Wrapper class in Java

Wrapper class in java are the Object representation of eight primitive types in java. All the wrapper classes in java are immutable and final.

Java 5 autoboxing and unboxing allows easy conversion between primitive types and their corresponding wrapper classes in java programs.

Wrapper Class in Java

Below table shows the primitive types and their wrapper class in java.

Why do we need wrapper classes?

I think it was a smart decision to keep primitive types and Wrapper classes separate to keep things simple. We need wrapper classes when we need a type that will fit in the Object-Oriented Programming like Collection classes. We use primitive types when we want things to be simple.

Primitive types can’t be null but wrapper classes can be null.

Wrapper classes can be used to achieve polymorphism.

Here is a simple program showing different aspects of wrapper classes in java.

WrapperClasses.java

package com.journaldev.misc;

import java.util.ArrayList;
import java.util.List;

public class WrapperClasses {

    private static void doSomething(Object obj){
        
    }
    
    public static void main(String args[]){
        int i = 10;
        char c = 'a';
        
        //primitives are simple to use
        int j = i+3;
        
        //polymorphism achieved by Wrapper classes, we can't pass primitive here
        doSomething(new Character(c));
        
        List<Integer> list = new ArrayList<Integer>();
        //wrapper classes can be used in Collections
        Integer in = new Integer(i);
        list.add(in);
        
        //autoboxing takes care of primitive to wrapper class conversion
        list.add(j);
        
        //wrapper classes can be null
        in = null;
    }
}