A package is a namespace that organizes a set of related classes and interfaces.
Package is a collection of classes, interfaces, multiple sub packages etc.
Some of the existing packages in Java are:
· java.lang - bundles the fundamental classes
· java.io - classes for input , output functions are bundled in this package
Advantages of packages -:
· Reusability: Reusability of code is one of the most important requirements in the software industry. Reusability saves time, effort and also ensures consistency. A class once developed can be reused by any number of programs wishing to incorporate the class in that particular program.
· Easy to locate the files.
· In real life situation there may arise scenarios where we need to define files of the same name. This may lead to “name-space collisions”. Packages are a way of avoiding “name-space collisions”.
Types of package:
1. User defined package: The package we create is called user-defined package.
2. Built-in package: The already defined package like java.io.*, java.lang.* etc are
known as built-in packages
// define package
package packagename;
// import packages
Import mypack;
//class declaration
class Sample
{
// instance members
//method implementation
}
}
Define a package
package <package name>;
Example of package of creation
package mypack;
class Book
{
String bookname;
String author;
Book(String b, String c)
{
this.bookname = b;
this.author = c;
}
public void show()
{
System.out.println(bookname+" "+ author);
}
}
class test
{
public static void main(String[] args)
{
Book bk = new Book("java","Herbert");
bk.show();
}
}
Access of package-:
Import.mypack;
import java.util.Date;
Subpackage in java-:
Package inside the package is called the subpackage. It should be created to categorize the package further.
Example of sub packages
package com.midstick.core;
class Sample{
public static void main(String args[]){
System.out.println("Demo subpackage");
}
}
package com.mindstick.core
import static java.lang.Math.*;
public class Test
{
public static void main(String[] args)
{
System.out.println(sqrt(144));
}
}
output -: 12
Leave Comment