Which Package Is Automatically Imported In Any Java Program?

Java lang package (java.lang) This packages contains the fundamental or core classes of java language without which it won’t be possible to write program in java. This package is automatically imported to each program, which means we can use the classes of this package directly in our program.
java. lang package is automatically imported.

Which package is imported by default in Java?

Which Package is Imported by Default in Java? In Java, the package is the collection of Java classes and interfaces. When we use the classes of a particular package, we need to import that particular package in which that classes are defined. The class uses the fully qualified name that includes the package name.

What is a package in Java?

In Java, the package is the collection of Java classes and interfaces. When we use the classes of a particular package, we need to import that particular package in which that classes are defined. The class uses the fully qualified name that includes the package name. In most of the basic Java programs, we do not import any package.

How do I import a class from another package in Java?

All we need to do is put related classes into packages. After that, we can simply write an import class from existing packages and use it in our program. A package is a container of a group of related classes where some of the classes are accessible are exposed and others are kept for internal purpose.

Which package is imported by default in Java?

Which Package is Imported by Default in Java? In Java, the package is the collection of Java classes and interfaces. When we use the classes of a particular package, we need to import that particular package in which that classes are defined. The class uses the fully qualified name that includes the package name.

What is a package in Java?

In Java, the package is the collection of Java classes and interfaces. When we use the classes of a particular package, we need to import that particular package in which that classes are defined. The class uses the fully qualified name that includes the package name. In most of the basic Java programs, we do not import any package.

What is a package with no name in Java?

In every Java program there can be one unnamed package, which is simply a package with no name. If you omit the package statement while writing the class definition, the class name is placed into the default package, which has no name. Java compiler automatically imports this package. Second, the java.lang package is imported implicitly.

Built in packages in Java – Predefined Packages

  • Built-in packages or predefined packages are packages that have already been specified and included in the Java program. These packages are referred to as built-in packages or preconfigured packages. These packages provide a huge number of classes and interfaces that are beneficial for java programmers who are working on a variety of different projects. Programmers can include these packages in their programs and make use of the classes and interfaces provided by these packages in their own programs, as well. The built-in packages are automatically included in your Java development kit or Java runtime environment download. The jar files that include these packages are used to distribute them. When you unzip the jar file, you will be able to see the packages that are contained within it. Using the example above, if you unzip the rt.jar file located in the lib folder of the JRE, you will notice the directory java, which contains packages such as lang, io, util and sql, among others, In Java, there are a plethora of built-in packages to choose from. The purpose of this tutorial is to introduce you to some of the built-in packages and show you how to utilize their classes in our application. Some of the pre-installed packages in Java are as follows: java.awt: This package contains classes for designing user interfaces as well as classes for painting graphics and pictures on the screen. This package contains classes such as Button, Color, Event, Font, Graphics, and Image, among others
  • java.io: This package contains classes for system input/output operations. This package contains classes and interfaces that are fundamental to the design of the Java programming language, such as BufferedReader and BufferedWriter, File, InputStream, OutputStream, PrintStream, Serializable, and so on. java.lang: This package contains classes and interfaces that are fundamental to the design of the Java programming language, such as BufferedReader and BufferedWriter, File, InputStream, OutputStream, PrintStream, Serializable, and so This package contains classes such as String, StringBuffer, System, Math, Integer, and so on
  • java.net: This package contains classes for developing and deploying networking applications. This package contains classes such as Authenticator, HttpCookie, Socket, URL, URLConnection, URLEncoder, URLDecoder, and others.
  • Java.sql: This package contains the classes necessary for accessing and processing data stored in a database in Java. Class types such as Connection, DriverManager, PreparedStatement, ResultSet, and Statement, among others, are contained inside this package.
  • This package contains the collections framework, as well as certain internationalization support classes, properties, and random number generating classes. java.util It contains classes such as ArrayList, LinkedList, HashMap, Calendar, Date, TimeZone, and so on
  • it also contains classes such as HashMap.
  • The list of all java packages may be found by unzipping the jar files, as previously said; alternatively, you can visit this page for the complete listing of all java packages accessible in Java 11.
  • Because the package java.lang is automatically imported into every program that we write, we don’t need to include an import line in our programs when utilizing classes such as String, StringBuffer, System, and so on.
  • Other packages, with the exception of java.lang, must be imported into your application before you may utilize the classes and interfaces that are available in those packages.
  • Refer to the package import tutorial for detailed instructions on how to import packages into a Java program.

Java awt package(java.awt)

  • This package, known as the Java AWT(Abstract Window Toolkit), comprises classes and interfaces that are used to construct graphical user interface (GUI) or window-based programs in Java.
  • Java AWT components are platform-dependent, as they make use of operating system resources to generate components such as textboxes, buttons, and checkboxes, among other types of controls.
  • The program that follows constructs a frame that contains a label by utilizing the java.awt classes and their counterparts.

Java awt package program

  • Import java.awt.Frame; import java.awt.Label; create a class using these imports.
  • The JavaAWTExample class has the following members: fm = new Frame(); Label lb = new Label(″ Welcome to refresh java″); fm.add(lb); fm.setSize(300, 200); fm.setVisible(true); public static void main() takes the following arguments: awt = new JavaAWTExample(); fm.add(lb); fm.setSize Here Frame and Label are two classes that are specified in the java.awt library.
  • To make a frame, the Frame class is used, and the Label class is used to generate a label.
  • Because of its platform requirement and heavy-weight nature, the AWT package is only seldom used these days.
  • Swing is the recommended API for designing graphical user interfaces in Java, as opposed to the AWT API.

Output:

Java lang package(java.lang)

  • This package includes the fundamental or core classes of the Java programming language, without which it would be impossible to construct a program in java.
  • This package contains the core classes of the Java programming language.
  • This package is automatically imported into each program, which implies that we may utilize the classes included inside this package immediately within our own program without any further effort.
  • The program below demonstrates how to make use of the Math class, which is part of the java.lang package and contains a plethora of methods for performing various mathematical operations.

Java program of demonstrating use of java.lang package

  • The following code is from the JavaLangExample class: public static void main(String args) a = 20, b =30; int sum = Math.addExact(a,b); int max = Math.max(a,b); double pi = Math.PI; System.out.printf(″Sum = ″+sum+″, Max = ″+max+″, PI = ″+pi); Sum = 50, Max = 30, and PI = 3.141592653589793 are the outputs.
  • As you can see, we are able to utilize the Math and System classes specified in the java.lang package without having to use an import statement.
  • This is because the java.lang package is imported implicitly, as demonstrated in the previous section.

Java io package(java.io)

  • The Java IO(Input/Output) package contains classes and interfaces that are used to handle system input and output activities (on computers, laptops, and other similar devices).
  • By utilizing these classes, a programmer may take in user input and perform actions on it, after which the outcome is displayed to the user In most cases, input is provided through the use of a keyboard or keypad.
  • Using the classes in this package, we can also do file handling (read/write) operations.
  • When a user enters information into a console, the java.io package’s Console class is used to receive that information and display it on the user’s screen (command prompt or any other terminal used).

Java program of demonstrating use of java.io package

  • Inherit java.io.Console; create a new JavaIOExample class with the following members: public static void main(String args); Console cs = System.console(); System.out.println(″Enter your name: ″); String name = cs.readLine(); System.out.println(″Welcome: ″+name); The first time you start this application, it will prompt you for your name, after which it will display your name in the terminal window.
  • Output: Fill in the blanks with your name: Rahul Welcome: Rahul

Java util package(java.util)

  • Java programmers can take advantage of the fundamental utility classes provided by the Java util package.
  • It is one of the most useful packages for Java programmers since it allows them to quickly and simply fulfill a variety of various needs by utilizing its preset classes.
  • An array of numbers is sorted using the Arrays class of this package, as seen in the program below.
  • The Arrays class provides a plethora of APIs (methods) to cater to a variety of array requirements.

Java program of demonstrating use of java.util package

Import java.util.Arrays; create a new JavaUtilExample class with the following members: public static void main(String args); int intArray =; Arrays.sort(intArray); System.out.printf(″Sorted array: percent s″, Arrays.toString(intArray)); java.util.Arrays import java.util.Arrays import java.util.Arrays import java. The following is the output: sorted array:

Which Package is Imported by Default in Java – Javatpoint

  • The package is a collection of Java classes and interfaces in the Java programming language.
  • When we want to utilize the classes from a certain package, we must first import the package that contains the classes we want to use.
  • The class makes use of the fully qualified name, which includes the package name, to identify itself.
  • We don’t import any packages in the majority of the fundamental Java apps.
  • In this case, the question arises as to how Java applications are able to make use of classes specified in a particular package when we do not import the package in question.

The Java Virtual Machine (JVM) internally resolves this problem by default importing the java.lang package.

java.lang Package

  • By default, the Java compiler includes the java.lang package in its internal representation.
  • It makes available the core classes that are required for the development of a basic Java program.
  • The most significant classes are Object, which serves as the base of the class hierarchy, and Class, which represents classes at run time through instances of the class.
  • Let’s write a Java application to determine whether a given integer is even or odd.
  • We haven’t imported any packages into this particular software.

Output from FindEvenOdd.java Take a look at the program above; we haven’t imported any packages at all.Despite this, we have made use of the String class.When creating a class, it is necessary to start with its fully qualified name, followed by the import keyword, at the top of the program.

  • We, on the other hand, have not done so.
  • This is due to the fact that the Java compiler by default imports the java.lang package, which contains the String class definition.
  • In order to determine whether this is true or false, we can decompile the Java program.
  • If you do not know how to decompile a Java program manually, you may utilize a Java decompiler online or go via the link process.
  • We have decompiled the aforementioned Java application and discovered that java.io is involved.
  • The PrintStream package is automatically imported.

The following is the hierarchy for importing the PrintStream class: In the hierarchy, it can be seen that the Object class of the java.lang package is imported by default by other classes.It indicates that the java.lang package is imported by default, but is not visible to the user.After decompiling the above program, the following is what the program looks like: As a result, we do not need to explicitly import the java.lang package.We may utilize the classes from the java.lang package in our Java application without having to import the package from the Java platform.

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Packages In Java

  • In Java, a package is a technique for encapsulating a collection of classes, subpackages, and interfaces into a single object. Packages are used for the following purposes:Preventing naming conflicts. For example, there can be two classes with the name Employee in two packages, college.staff.cse.Employee and college.staff.ee.Employee
  • and there can be two classes with the name Employee in two packages, college.staff.cse.Employee and college.staff.ee.Employee.
  • Making it easy to search for and locate classes, interfaces, enumerations, and annotations, as well as to use them
  • Protected and default have access control at the package level, allowing for more regulated access. All classes in the same package, as well as their subclasses, have access to a protected member. A default member (one that does not have an access specifier) is only available by classes that are part of the same package.
  • Packages can be thought of as data encapsulation (also known as data concealing).
  • All that is required is the organization of related classes into packages. After that, we can easily develop an import class that pulls in data from existing packages and incorporate it into our application. A package is a container for a collection of related classes, some of which are visible to the public and others which are reserved for internal use. There is no limit to the number of times we may reuse existing classes from the packages in our application. What is the procedure for sending packages? The names of packages and the structure of their directories are tightly connected. Consider this scenario: if a package’s name is ″college.staff.cse,″ then there are three directories with the names ″college,″ ″staff,″ and ″cse,″ with cse present in staff and college present in cse. The directory college is also accessible through the CLASSPATH variable, which means that the path to the college’s parent directory is included in the CLASSPATH variable. The objective is to make sure that classes are easy to find while searching for them. naming standards for packages: Packages are named in the opposite order of the domain names, for example, org.geeksforgeeks.practice instead of org.geeksforgeeks. If you’re at a college, for example, the suggested convention is college.tech.cse, college.tech.ee, college.art.history, or any variation on that theme. Adding a class to a Package is as follows: By including the package name at the start of the program and putting it in the package directory, we may expand the functionality of a previously developed set of classes. If we want to define a public class, we must create a new java file
  • otherwise, we may add the new class to an existing.java file and recompile it. Subpackages are packages that are contained within another package and are referred to as subpackages. These are not automatically imported
  • instead, they must be imported explicitly. Additionally, members of a subpackage do not have access rights, i.e., they are treated as a separate package for the purposes of protected and default access specifiers. As an illustration, import java.util.*
  • util is a subpackage that was developed within the java package. Getting at classes contained within a package Take a look at the following two statements: The Vector class from the util package is imported with the keyword import java.util.vector
  • / all of the classes from the util package are imported using the keyword import java.util.*
  • The first statement is used to import the Vector class from the util package, which is included within the Java runtime environment.
  • It imports all of the classes from the util package in the second sentence.
  1. Package.*
  2. / Only the classes and interfaces mentioned in this package will be accessible
  3. however, subpackages will not be accessible. import package.*
  4. / Only the classes and interfaces of this package will be accessible. import package.classname
  5. / import package.classname
  6. When two packages have the same / class name, it is common practice to utilize the class name. For example, in the code below, both packages contain the / date class
  7. hence, a fully qualified name is used to avoid a conflict. I’ve included imports for date and vector, as well as imports for my package’s date and vector, and public classes for both. ImportDemo public static void main(String arg) ImportDemo public static void main() Packages are classified into the following categories: Packages that are pre-installed These packages contain a significant number of classes that are a component of the Java programming language’s API. The following are examples of widely used built-in packages: 1) java.lang: This package contains classes that provide language support (e.g classed which defines primitive data types, math operations). This package is imported without user intervention. 2) java.io: This package contains classes that are used to facilitate input and output operations. 3rd class: java.util: This package contains utility classes that implement data structures such as Linked List and Dictionary, and also provides support for Date and Time operations. 4) java.applet: This package contains classes for generating Applets in Java. It contains classes for creating the components of graphical user interfaces (GUIs). It is part of the Java Awt package (like button,
  8. Menus etc). 6) java.net: This package contains classes for assisting with networking activities. Packages created by the user These are the packages that have been defined by the end user or administrator. To begin, we create a directory named myPackage (name should be same as the name of the package). then construct a class named MyClass inside of that directory with its first statement including the package names as its parameters. / • The package’s name must correspond to that of the directory / in which this file is saved package public class myPackage
  9. myPackage MyClass consists of the public void getNames(String s) and the System.out.println(s) functions. We can now include the MyClass class into our software. /* import the ‘MyClass’ class from the ‘names’ myPackage */ import the myPackage.MyClass public class from the ‘names’ myPackage In this example, the String variable is initialized with the string name = ″GeeksforGeeks″
  10. / In this example, the class MyClass is created in the package. In the following example, MyClass obj = new MyClass()
  11. obj.getNames(name)
  12. Please keep in mind that MyClass.java must be saved within the myPackage directory because it is a component of the package. Making Use of Static Import When using the Java programming language (versions 5 and higher), static import is a feature that allows members (fields and methods) specified in a class as public static to be utilized in Java code without mentioning the class in which the field is defined. The following program shows how to use static import: import static java.lang.System.*
  13. Class StaticImportDemo
  14. import static java.lang.System.*
  15. Class StaticImportDemo GeeksforGeeks is the final product. Handling name disputes is a complicated process. The only time we need to pay attention to packages is if there is a naming dispute between two of them. For example, the Date class is found in both the java.util and the java.sql packages, respectively. As a result, if we import the following two packages into the program: • • • • • • • • • • • • • • • • • • • • • • • • • If we use the Date class after that, we will receive the following compile-time error: Date today
  16. /ERROR- java.util.Date or java.sql.Date? When it comes to Date classes, the compiler will not be able to figure out which one we want. It is possible to resolve this issue by employing the following import statement: import java.util.Date
  17. import java.sql.*
  18. import java.sql.*
  19. Consequently, if we require both Date classes, we must use the whole package name every time we declare a new instance of that type. As an illustration: java.util.Date Java.sql.Date today = new java.sql.Date()
  20. deadLine = new java.util.Date()
  21. Directory structure = new java.sql.Date()
  22. The name of the package is strongly related with the directory structure that is used to store the classes in that package. The classes (and other things) that belong to a single package are all stored in the same directory as the package itself. Furthermore, they are stored in a sub-directory structure that is provided by the package name that was used to create them. If the class Circle is found in package com.zzz.project1.subproject2, it will be kept in the following format: ″$BASE DIRcom.zzz.project1 subproject2Circle.class,″ where $BASE DIR signifies the package’s root directory. In this case, it is clear that the ″dot″ in the package name refers to a subdirectory of the file system. This means that the base directory ($BASE DIR) can be found anywhere in the file system’s hierarchy. As a result, in order for the Java compiler and runtime to identify the classes, the location of the $BASE DIR must be sent to them. This is performed through the use of an environment variable known as CLASSPATH. It is analogous to another environment variable PATH, which is used by the command shell to look for executable applications in the directory where they are stored. Setting the CLASSPATH: The CLASSPATH can be established in a variety of methods, including the following: CLASSPATH may be established permanently in the environment by using the following command: Select Control Panel from the Start menu in Windows. System? Advanced? Variables in the environment? Choose between ″System Variables″ (which affects all users) and ″Person Variables″ (which affects only the user who is currently logged in). If CLASSPATH already exists, should you select ″Edit″ or ″New″? Do you want to use the variable name ″CLASSPATH″? As the value, enter the path to the appropriate folders and JAR files (separated by semicolons), for example, ″.
  23. C:javaprojectclasses
  24. D:tomcatlibservlet-api.jar″ Keep in mind that you must include the current working directory (denoted by the letter ‘.’) in the CLASSPATH variable. To determine the current configuration of the CLASSPATH variable, use the following command:> THE SET CLASSPATH command may be used to set the CLASSPATH variable for the duration of a CMD shell session by executing the following command:> SET CLASSPATH=.
  25. C:javaprojectclasses
  26. D:tomcatlibservlet-api.jar
  27. SET CLASSPATH=.
  28. C:javaprojectclasses
  29. SET CLASSPATH=.
  30. C:javaprojectclasses
  31. Instead of utilizing the CLASSPATH environment variable, you can use the command-line options -classpath or -cp of the javac and java commands, for example,> java –classpath or> java –classpath. com.abc.project1.subproject2.MyClass3 is located in the c:javaprojectclasses directory. User-defined packages are illustrated as follows: Creating our first package entails the following steps: ClassOne.java is the file name
  32. package name is the package name
  33. public class name is ClassOne is a kind of class. Creating our second package entails the following steps: Name of the file: ClassTwo.javapackage package one
  34. Public class ClassTwo ClassTwo Making use of both of the packages that have been created: File name: Testing.javaimport package one.ClassTwo
  35. Import package name.ClassOne
  36. Public class Testing
  37. Import package name.ClassTwo
  38. Public class Testing Hello, my name is ClassTwo and I’d like to introduce myself. The name is ClassOne, and I’m here to welcome you. After that, we’ll have a look at the directory structure of both package files and the testing class file: The following are important points:
  1. Every class is a component of a larger package.
  2. The classes in the file are placed in a special unnamed package (which is the same nameless package for all files) if no package is given
  3. otherwise, the classes are placed in a special named package.
  4. All classes and interfaces included within a single file are members of the same package. It is possible to provide the same package name in several files.
  5. The file must be located in a subfolder named name (i.e., the directory name must match the package name) if package name is supplied
  6. otherwise, it must be located in a subdirectory named name if package name is not specified
  7. Accessing public classes in another (named) package may be accomplished by using the syntax: package-name.class-name
  • Articles that are related: Nikhil Meherwal and Prateek Agarwal have contributed to this article, which is titled ″Quiz on Packages in Java.″ If you like GeeksforGeeks and would like to contribute, you can write an article using write.geeksforgeeks.org or send your article to [email protected]
  • If you like GeeksforGeeks and would like to contribute, you can also use write.geeksforgeeks.org or send your article to [email protected]
  • See your article appear on the GeeksforGeeks main page and assist other Geeks by sharing it with them.
  • Please leave comments if you see anything that is inaccurate or if you have further information to give regarding the subject matter addressed above.
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Which Packages Are Imported By Default in Java?

  • In order to provide a speedy response, three packages are automatically imported for each source file.
  • First and foremost, there is the box with no name.
  • The second package is the java.lang package.
  • Third, the existing legislative package (the package in which the current file is defined).
  • Every Java application may have one or more unnamed packages, which are simply packages that do not have a name.

If you do not include the package statement while writing the class definition, the class name is placed in the default package, which does not have a named package.This package is automatically imported by the Java compiler.Second, the java.lang package is imported without the user having to do anything.

  • Java is a true object-oriented programming language, which means that code is expressed in the form of classes rather than procedures.
  • Types are the components of a class that make up the class.
  • Built-in or basic types, as well as types derived from components, are the two categories of types in Java.
  • When it comes to components, primitive types may be used directly, but component types must typically be purchased from an external library by importing them from the relevant package.
  • Bringing a component into scope is the technical term used to describe the process of ordering a component from a library.
  • The java.lang package, which is included by default in the Java standard libraries, provides a number of components that are extremely often used in Java programs and is part of the Java standard libraries.

As a result, Java is rendered ineffective without most of the functionality contained in java.lang, which is why java.lang is automatically imported by the compiler for all projects.However, it is possible to import the same package or the same class more than once.Although neither the compiler nor the JVM will complain if you explicitly import java.lang in your program, the JVM will internally load the needed class only once, regardless of how many times you explicitly import the same class in your program.Third, the current package is the one that contains the definition of the class that is now being executed.The Java compiler automatically imports the currently selected Java package.I hope you have enjoyed learning about Java packages that are automatically imported.

Please contact us if you have any suggestions or comments, or if you see any typographical or grammatical errors on this page.Thank you for taking the time to read this!

About the Author

Is the founder of cs-fundamentals.com and the primary contributor to the site. He is a software professional (with a postgraduate degree from BITS-Pilani) who enjoys writing technical essays on topics such as programming and data structure design.

Which Packages Are Imported By Default in Java?

  • In order to provide a speedy response, three packages are automatically imported for each source file.
  • First and foremost, there is the box with no name.
  • The second package is the java.lang package.
  • Third, the existing legislative package (the package in which the current file is defined).
  • Every Java application may have one or more unnamed packages, which are simply packages that do not have a name.

If you do not include the package statement while writing the class definition, the class name is placed in the default package, which does not have a named package.This package is automatically imported by the Java compiler.Second, the java.lang package is imported without the user having to do anything.

  • Java is a true object-oriented programming language, which means that code is expressed in the form of classes rather than procedures.
  • Types are the components of a class that make up the class.
  • Built-in or basic types, as well as types derived from components, are the two categories of types in Java.
  • When it comes to components, primitive types may be used directly, but component types must typically be purchased from an external library by importing them from the relevant package.
  • Bringing a component into scope is the technical term used to describe the process of ordering a component from a library.
  • The java.lang package, which is included by default in the Java standard libraries, provides a number of components that are extremely often used in Java programs and is part of the Java standard libraries.

As a result, Java is rendered ineffective without most of the functionality contained in java.lang, which is why java.lang is automatically imported by the compiler for all projects.However, it is possible to import the same package or the same class more than once.Although neither the compiler nor the JVM will complain if you explicitly import java.lang in your program, the JVM will internally load the needed class only once, regardless of how many times you explicitly import the same class in your program.Third, the current package is the one that contains the definition of the class that is now being executed.The Java compiler automatically imports the currently selected Java package.I hope you have enjoyed learning about Java packages that are automatically imported.

Please contact us if you have any suggestions or comments, or if you see any typographical or grammatical errors on this page.Thank you for taking the time to read this!

About the Author

Is the founder of cs-fundamentals.com and the primary contributor to the site. He is a software professional (with a postgraduate degree from BITS-Pilani) who enjoys writing technical essays on topics such as programming and data structure design.

Packages in Java – organizing types in Java

Last edited on December 15, 2021. Table of contents Previous Next Java packages are discussed in detail in this section of the Java tutorial. When you group similar types together, you may provide access security and name space management for the group. Packages in Java are analogous to namespaces in C in terms of functionality.

Creaging a package in Java

  • The package keyword is used to identify a particular package.
  • This remark must be included at the start of each and every source-code document.
  • There can only be one sentence like this in a single source file.
  • The Java source files must be stored in folders that are named after the package in which they are to be used.
  • package Package name: com.zetcode; This package contains all of the types declared in the file associated with the aforementioned package.

The fully qualified name of a class named Being is com.zetcode.Being.Java programmers number in the millions all over the world.

  • In order to eliminate any name conflicts, the Java programming language has a naming standard.
  • The package names are based on Internet domain names that have been inverted.
  • The letters are written in lowercase for readability.
  • Because there can only be one zetcode.com domain name, using the reversed name com.zetcode for the packages will distinguish them from one another.
  • com.zetcode package must be included in the Java source file, which must be located in the com/zetcode subdirectory.
  • Package names are written entirely in lower case in order to minimize confusion with the names of classes or interfaces within the package.

It is used at the beginning of a source file to define types (classes, interfaces, enumerations, or annotations) or complete Java packages that will be referred to later without specifying their package names in the referenced source file.Since Java SE 5.0, import statements may be used to import static members of a class that is being imported (methods and variables).import java.awt.*; We may import the entire package at once by using the wildcard character *.Following this import, we will be able to refer to all of the types in the java.awt package without having to use their fully qualified names.It is not necessary to import java.awt.event.* as part of the java.awt.* import because it is included in the java.awt.event subpackage’s namespace.Subpackages must be imported separately from the main package.

import java.util.Random; In this scenario, just the Random class is imported from the source code.The Random class can now be referred to by its basic class name instead of its full name.

Core packages in Java 8

  • Listed below is a comprehensive list of Java 8’s most important packages: Java.lang provides basic language capabilities and fundamental types
  • java.util provides collection data structure classes
  • and java.sql provides SQL-like capability.
  • Java.io is a Java API for performing file operations.
  • Java.math – arithmetics with several precisions
  • Java.nio is a non-blocking I/O framework for Java
  • java.net is a networking framework that supports sockets and DNS lookups
  • and java.sockets is a socket-based I/O framework for Java.
  • Java.security contains functions for key creation, encryption, and decryption.
  • JDBC (Java Database Connectivity) is used to connect to databases in java.sql.
  • Basic package hierarchy for native GUI components in Java
  • java.awt — the most basic package hierarchy for native GUI components
  • Javax.swing is a package hierarchy that contains platform-independent rich graphical user interface components.
  • Java.applet consists of classes for developing applets in Java.
  • Java.beans—Contains classes that are used in the development of beans, which are components that are based on the JavaBean architecture.
  • Text-handling classes and interfaces that are independent of natural language are provided by the java.text package. text-handling classes and interfaces are provided by the java.text package.
  • Java.rmi is a Java API for invoking methods from a remote location.
  • JRE java.time — This is the primary API for dealing with dates, times, instants, and durations.

The java.lang package can be accessed without the need for an import line in the code.

Practical example

  • Creating a package and importing types are demonstrated in the following example.
  • Packages.java package com.zetcode; import java.util.Random; public class Packages { public static void main(String args) { Random r = new Random(); int x = r.nextInt(); System.out.println(x); java.util.Calendar c = java.util.Calendar.getInstance(); System.out.println(c.getTime()); } } The example makes use of two types: the Random class and the Calendar class, both of which are derived from the same base class.
  • The first class is imported, and the second class is referred to by its fully qualified name in the second class definition.
  • package com.zetcode; Using the package keyword, we may declare a new package.
  • Packages.java must be located in the com/zetcode subfolder in order to function properly.

import java.util.Random; This code line enables us to utilize the Random class without the package name.Random r = new Random(); Here we utilize the Random without mentioning its entire name.java.util.Calendar c = java.util.Calendar.getInstance(); If we did not utilize the import keyword on a type, we may refer to it just by its complete name – java.util.Calendar in our case.

  • The import keyword saves a lot of typing.
  • $ ls com/zetcode/ Packages.java The Packages.java source file is placed in the com/zetcode subfolder.
  • The package name must reflect the directory structure.
  • $ javac com/zetcode/Packages.java We build the source file with the javac tool.
  • The tool is called from the parent directory of the com/zetcode directory.
  • $ java com.zetcode.Packages 179489124 Thu Jan 19 20:53:08 CET 2017

Java package-private visibility

It is possible to have a package-private visibility if we do not provide an access modifier (e.g., private, protected, or public). It is possible to access variables and methods from inside the same package in this situation. Classes and members defined with package-private access cannot be accessed by classes and members in other packages.

Java default package

  • If no package is specified in the file, all types described in that file are considered to be part of a default, unidentified package.
  • It is suggested that you keep your kinds in a sealed package at all times.
  • Even for tiny initiatives, it’s important to be creative.
  • DefaultPackage.java is a public class that may be used to create a package.
  • DefaultPackage public static void main(String args); System.out.println(″A class in a default package″); DefaultPackage public static void main(String args); The default package includes the DefaultPackage class, which is defined as follows: ls DefaultPackage.java $ ls DefaultPackage.java In the absence of a package, the source file is not placed in a specified subfolder of the current directory.

$ javac DefaultPackage.java $ javac DefaultPackage.java java DefaultPackage $ java DefaultPackage A class that is included in the default package It is necessary to compile the code before running the program.The source file and the bytecode are both located in the current working directory of the application.

Java automatic imports

  • Automatically, the Java compiler imports two packages: java.lang and the current package, which are both required.
  • Constants.java package com.zetcode; public class Constants public static final String version = ″1.0″; com.zetcode Constants.java package com.zetcode Constants.java package com.zetcode Constants.java package com.zetcode The Constants class is situated in the same package as the AutomaticImports class, which is referring to the version member of the Constants class in its reference.
  • Package AutomaticImports.java is owned by the com.zetcode organization.
  • Public class AutomaticImports has the following members: public static void main(String args) String os = System.getProperty(″os.name″); System.out.println(os); System.out.println(Constants.version); String os = System.getProperty(″os.name″); String o In this example, we are referring to several classes that are automatically imported by the Java compiler when the program is executed.
  • In this case, the string os is equal to System.getProperty(″os.name″); java.lang contains the String and System classes, which are both used by the Java programming language.

System.out.println(Constants.version); The Constants class, which is placed in the same package as the AutomaticImports class, is used to print the version of the constants.As a result, we are able to access the class and its members without having to use the fully qualified name or the import keyword to do this.$ ls com/zetcode/AutomaticImports.java AutomaticImports.java Constants.java Both the AutomaticImports.java and the Constants.java files are contained in the same subfolder of the project.

  • $ javac com/zetcode/AutomaticImports.java com/zetcode/Constants.java com/zetcode/AutomaticImports.java Both of the files have been assembled.
  • AutomaticImports Linux 1.0 is imported by $ java com.zetcode.AutomaticImports Linux 1.0.
  • A screenshot of the com.zetcode.AutomaticImports program’s output may be seen in the next section.
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Java static imports

  • If we frequently refer to some static members, we may utilize the import static statement to refer to them without having to type the complete class name in the future.
  • The usage of static imports should be done with extreme caution.
  • staticImport.java file in the root package com.zetcode; import static java.lang.Math.E; import static java.lang.Math.PI; import static java.lang.Math.abs; public class staticImport.java file in the root package com.zetcode The StaticImport function is a public static void main(String args) that calls System.out.println(E); System.out.println(PI); System.out.println(abs(-5)); and other functions.
  • Throughout this example, we will make use of two constants and a static method.
  • It is necessary to use the import static statement in order to refer to them without their complete names, as in: import static java.lang.Math.E; import static java.lang.Math.PI; import static java.lang.Math.abs; System.out.println(E); System.out.println(PI); System.out.println(abs(-5)); These three members are referred to as ″System.out.println(E); System.out.println(PI); System.out.println(abs(-5)); $ java com.zetcode.StaticImport 2.718281828459045 3.141592653589793 5 2.718281828459045 3.141592653589793 5 The topic of packages in Java was explored in this chapter.

We’ve demonstrated how to structure our code into packages.Table of Contents Previous Page of Next

Using Package Members (The Java™ Tutorials > Learning the Java Language

  • Those kinds that are included in a package are referred to as package members. For a public package member to be used outside of its package, one of the following actions must be taken. In all cases, refer to the member by his or her entire legal name.
  • Import the package member into the program.
  • Import the whole package from the member

Each is suited for a distinct context, as will be detailed in further detail in the next sections.

Referring to a Package Member by Its Qualified Name

Each is suited for a certain context, as detailed in further detail in the following sections.

Importing a Package Member

  • A specific member into the current file can be imported using an import statement, which should be placed before any type definitions but after the package statement, if there is one, at the beginning of the file.
  • Using the graphics package you built in the previous part, you can import the Rectangle class.
  • Here’s how to do that.
  • graphics.Rectangle is imported; You will now be able to refer to the Rectangle class by its short name.
  • new Rectangle(); Rectangle myRectangle = new Rectangle() This method is effective if you just need to use a few members from the graphics package.

However, if you want to utilize a large number of types from a package, you should import the full package.

Importing an Entire Package

  • To import all of the types included within a certain package, use the import statement with the asterisk (*) wildcard character in the import statement.
  • You may now refer to any class or interface in the graphics package by its short name instead of its full name.
  • Circle myCircle = new Circle(); myRectangle = new Rectangle(); myCircle = new Circle(); Asterisks are only allowed to be used in the import statement to indicate all of the classes contained inside a package, as demonstrated above.
  • When searching for a subset of the classes in a package, it cannot be utilized.
  • In the graphics package, for example, the following does not match all of the classes that begin with the letter A.

/ does not function properly when importing graphics.A*; instead, it creates a compiler error message.In most cases, the import statement is used to import a single package member or a whole package.Keep in mind that you may also import the public nested classes of an enclosing class using a different, less popular type of import.

  • For example, if the graphics.Rectangle class contained useful nested classes such as Rectangle.DoubleWide and Rectangle.Square, you could import Rectangle and its nested classes by using the following two statements: import Rectangle and its nested classes; import Rectangle and its nested classes; import Rectangle and its nested classes; import Rectangle and its nested classes; import Rectangle and its nested classes; import graphics.Rectangle; import graphics.Rectangle.*; import graphics.Rectangle.
  • Rectangle will not be imported by the second import statement, so keep that in mind.
  • The static import statement, which is a less frequent type of import statement, will be described at the conclusion of this section.
  • The Java compiler automatically imports two complete packages for each source file, which is done for your convenience: Specifically, (1) the java.lang package and (2) the currently installed package (the package for the current file).

Apparent Hierarchies of Packages

  • Packages appear to be hierarchical at first glance, however this is not the case.
  • For example, the Java API offers several packages that begin with the prefix java.awt, such as the java.awt.color package, the java.awt.font package, and many more that begin with the prefix java.awt.
  • There are certain packages that are not included in the java.awt package, such as the java.awt.color package and the java.awt.font package, as well as additional packages in the java.awt.xxxxxx package.
  • The prefix java.awt (the Java Abstract Window Toolkit) is used for a variety of related packages to indicate their relationship, rather than to indicate that they are included in the group.
  • It is possible to import all of the types in the java.awt package by using the java.awt.* import command, but it is not possible to import the java.awt.color, the java.awt.font, or any other java.awt.xxxxxx packages by specifying the java.awt.xxxxxx command.

In order to utilize the classes and other kinds in java.awt.color as well as the classes and other types in java.awt, you must import both packages, together with all of their files: import both packages, along with all of their files import java.awt.*; import java.awt.color.*; import java.awt.color.*;

Name Ambiguities

  • If a member in one package has the same name as a member in another package, and both packages are imported, you must refer to each member by the qualified name that it was assigned when the package was created.
  • For example, the graphics package has a class named Rectangle that may be used.
  • Rectangle is a class that may be found in the java.awt package.
  • The following is unclear if both graphics and java.awt have been loaded into the project.
  • It is necessary to utilize the member’s fully qualified name in this circumstance in order to specify the Rectangle class you want.

As an illustration,

The Static Import Statement

  • If a member in one package has the same name as a member in another package, and both packages are imported, you must refer to each member by the qualified name that it was assigned when the member was created.
  • Examples include a class named Rectangle that was defined by the graphics package.
  • Rectangle is a class that is included in the java.awt package.
  • The following is unclear if both graphics and java.awt have been imported into the system.
  • It is necessary to use the fully qualified name of the member in this scenario in order to specify which Rectangle class you want.

Think of it this way:

Which is default package imported in every Java programming?

By default, the Java compiler includes the java.lang package in its internal libraries. It makes available the core classes that are required for the development of a basic Java program.

Which package is always imported by default?

By default, the java.lang package is always included in the import path.

What is import package in Java?

It is necessary to utilize the Java import keyword in order to import a java package into a class. This keyword is used to access a package and its classes within a java application. In order for your class to refer to a class that is located in another package by utilizing its name directly, import must be used to access built-in and user-defined packages within your java source code file.

What is meant by default package in Java?

The default package is a collection of Java classes whose source files do not contain any package declarations and which are not included in the default package. These packages serve as the default package for classes of this kind. This feature makes it convenient for developers to quickly create tiny apps while the development of a project or application is just getting started.

Which package is imported to all classes in Java?

All of the classes from the util package are imported in the second sentence.

Which Java package is automatically imported?

Java. lang package and (2) the current package are automatically imported by the Java compiler for the sake of convenience when a source file is opened with the Java compiler (the package for the current file).

Which Java package is automatically imported in a Java program?

The package java.lang is automatically loaded into the project.

What is a package in programming?

It is possible to group together similar classes and interfaces using the namespace package…. Class options are virtually limitless, with literally hundreds to select from. This frees up your time as a programmer to concentrate on the design of your specific application rather than the infrastructure necessary to make it operate.

Can we import packages in Java?

Using Java’s import statement, you may either import a whole package, as was done in the previous examples, or utilize only the classes and interfaces declared in the package. Java does not need the use of an import statement.

What is package in Java Mcq?

An A package is a collection of files of the types Java Class, Java Interface, or Java Abstract Class that are used together.

Which is default package imported in every Java programming Mcq?

By default, the Java compiler includes the java.lang package in its internal libraries. It makes available the core classes that are required for the development of a basic Java program.

What is default package eclipse?

If you’ve been using Eclipse for a while, you’ve undoubtedly noticed that the new classes you build don’t just appear in the list of available classes. They are grouped together under the ″default package″ node in the hierarchical structure. In this case, because your class is not assigned to a package, it will be grouped with all of the other non-packaged classes in the default package.

What is a default class in Java?

Default. When we don’t explicitly provide access to a class, method, or property, Java will set a default access to that class, method, or property. Package-private is another name for the default access modifier, which indicates that all members are visible inside a single package but are not available from other packages: package com.

Which is root packages for all the packages in Java?

It is the root class in Java, i.e., it is the super class of every user-defined/predefined class in the language. The Object class is found in the java.lang package. This class contains methods that are implemented by all objects, including arrays.

What package is a part of the wrapper class which is imported by default into all Java programs Java Lang Java AWT Java IO Java Util?

The Object class in the java.lang package is the root class in Java, which means it is the super class of every user-defined/predefined class in the language. It is specified in the Java language specification. The methods of this class are implemented by all objects, including arrays, in some way.

What are the types of packages in Java?

  • The built-in package and the user-defined package are the two types of packages that may be found in Java.
  • In addition to the standard Java and Lang packages, there are many more built-in packages such as Awt and javax.
  • There are also several built-in packages such as net, io, util and sql.
  • Here, we will go through the specifics of building and utilizing user-defined packages in greater depth.

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