Wrapper Classes in Java (original) (raw)

Last Updated : 6 Apr, 2026

In Java, wrapper classes allow primitive data types to be represented as objects. This enables primitives to be used in object-oriented features such as collections, generics, and APIs that require objects.

• Each wrapper class encapsulates a corresponding primitive value inside an object (e.g., Integer for int, Double for double).
• Java provides wrapper classes for all eight primitive data types to support object-based operations.

**Example: Converting Primitive to Wrapper (Autoboxing)

Java `

class Geeks { public static void main(String[] args) {

    int b = 357;
    
    // Autoboxing: primitive int -> Integer object
    Integer a = b;

    System.out.println("The primitive int b is: " + b);
    System.out.println("The Integer object a is: " + a);
}

}

`

Output

The primitive int b is: 357 The Integer object a is: 357

**Explanation: Here, the primitive int value is automatically converted into an Integer object by Java. This automatic conversion is called autoboxing.

Why Wrapper Classes Are Needed

Wrapper classes are required in Java for the following reasons:

• Java collections (ArrayList, HashMap, etc.) store only objects, not primitives.
• Wrapper objects allow primitives to be used in object-oriented features like methods, synchronization, and serialization.
• Objects support null values, while primitives do not.
• Wrapper classes provide utility methods such as compareTo(), equals(), and toString().

**Autoboxing and Unboxing

**1. Autoboxing

The automatic conversion of primitive types to the object of their corresponding wrapper classes is known as autoboxing. For example: conversion of int to Integer, long to Long, double to Double, etc.

Java program to demonstrate the automatic conversion of primitive to wrapper class (Autoboxing).

Java `

import java.util.ArrayList;

class Geeks { public static void main(String[] args) { char ch = 'a';

    // Autoboxing: char -> Character
    Character c = ch;

    ArrayList<Integer> list = new ArrayList<>();
    // Autoboxing: int -> Integer
    list.add(25);
    System.out.println(list.get(0));
}

}

`

**2. Unboxing

Unboxing is the automatic conversion of a wrapper class object back into its corresponding primitive type.

Java `

import java.util.ArrayList;

class Geeks { public static void main(String[] args) {

    Character ch = 'a';
    // Unboxing: Character -> char
    char c = ch;

    ArrayList<Integer> list = new ArrayList<>();
    list.add(24);
    // Unboxing: Integer -> int
    int num = list.get(0);

    System.out.println(num);
}

}

`

Java Wrapper Classes Example

Java `

class Geeks { public static void main(String[] args) {

    byte b = 1;
    Byte byteObj = Byte.valueOf(b);

    int i = 10;
    Integer intObj = Integer.valueOf(i);

    float f = 18.6f;
    Float floatObj = Float.valueOf(f);

    double d = 250.5;
    Double doubleObj = Double.valueOf(d);

    char c = 'a';
    Character charObj = c; // autoboxing

    System.out.println("Wrapper Objects:");
    System.out.println(byteObj);
    System.out.println(intObj);
    System.out.println(floatObj);
    System.out.println(doubleObj);
    System.out.println(charObj);

    // Unboxing
    byte bv = byteObj;
    int iv = intObj;
    float fv = floatObj;
    double dv = doubleObj;
    char cv = charObj;

    System.out.println("\nUnwrapped values:");
    System.out.println(bv);
    System.out.println(iv);
    System.out.println(fv);
    System.out.println(dv);
    System.out.println(cv);
}

}

`

**Output:

Output

Primitive Data Types & Wrapper Classes

Common Methods of Wrapper Classes