Java Packages

1. Built-in Packages

The Java API provides hundreds of ready-to-use classes organized into packages such as java.util, java.io, java.time, and more.

Importing a single class

import java.util.Scanner;

public class DemoImport {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter your name:");
        String name = sc.nextLine();
        System.out.println("Hello " + name);
    }
}

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Importing an entire package

import java.util.*;

public class DemoList {
    public static void main(String[] args) {
        List names = Arrays.asList("Amit", "Ravi", "Neha");
        for (String n : names) {
            System.out.println(n);
        }
    }
}

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2. User-defined Packages

You can create your own packages to keep code modular and maintainable. A package corresponds to a folder structure.

Example: Creating a package

package mypack;

public class MyPackageClass {
    public void greet() {
        System.out.println("Hello from mypack!");
    }

    public static void main(String[] args) {
        MyPackageClass obj = new MyPackageClass();
        obj.greet();
    }
}

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Using a class from a user-defined package

import mypack.MyPackageClass;

public class UsePackage {
    public static void main(String[] args) {
        MyPackageClass obj = new MyPackageClass();
        obj.greet();
    }
}

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