Wrapper classes in java

Introduction

Java mein primitive data types hote hain jaise int, char, boolean, etc. Lekin Java ek object-oriented language hai, aur kabhi-kabhi humein objects ki zarurat padti hai instead of primitives. Yahi kaam karti hain Wrapper Classes. Wrapper Classes primitive data types ko objects mein convert karne ke liye use hote hain.

Primitive vs Wrapper Example

Primitive Wrapper Class

int → Integer

char → Character

boolean → Boolean

byte → Byte

short → Short

long → Long

float → Float

double → Double

Kyu Zarurat Hai Wrapper Classes Ki?

1. Collections ke sath kaam karne ke liye – Java Collections (like ArrayList) sirf objects handle karte hain.
2. Utility Methods chahiye – Wrapper classes mein kai helpful methods hote hain.
3. Conversion between types – String se number, number se string, etc.

Autoboxing and Unboxing

Java mein Wrapper classes ka use easy banane ke liye Autoboxing aur Unboxing exists karta hai.

• Autoboxing: Primitive → Object. Autoboxing mein Primitive data type se Object mein conversion hota hai.

int num = 10;
Integer obj = num;  // Autoboxing

• Unboxing: Object → Primitive. Unboxing mein reverse hota hai, Object se primitive data type mein conversion hota hai.

Integer obj = 20;
int num = obj;  // Unboxing

Examples with Explanation

Example 1: Integer ke sath kaam

public class WrapperExample {
    public static void main(String[] args) {
        int num = 100;
        Integer obj = Integer.valueOf(num); // manually boxing
        int unboxed = obj.intValue();       // manually unboxing

        System.out.println("Object: " + obj);
        System.out.println("Primitive: " + unboxed);
    }
}

Example 2: ArrayList mein Wrapper ka use

import java.util.ArrayList;

public class WrapperArrayList {
    public static void main(String[] args) {
        ArrayList<Integer> list = new ArrayList<>();

        list.add(10); // Autoboxing
        list.add(20);

        int sum = list.get(0) + list.get(1); // Unboxing
        System.out.println("Sum: " + sum);
    }
}

Useful Methods in Wrapper Classes

• Integer.parseInt("123") → String ko int mein convert karta hai.
• Integer.toString(100) → int ko String mein convert karta hai.
• Character.isLetter('a') → true return karega agar character letter hai.
• Boolean.parseBoolean("true") → String ko boolean mein convert karta hai.