Java Autoboxing and Unboxing with examples

Primitive type	Wrapper class
boolean Boolean
byte Byte
char Character
float Float
int Integer
long Long
short Short
double Double

When does the autoboxing and unboxing happens in Java

Autoboxing

class AutoboxingExample1
{
public static void myMethod(Integer num){
System.out.println(num);
}
public static void main(String[] args) {
/* passed int (primitive type), it would be
* converted to Integer object at Runtime
*/
myMethod(2);
}
}
2
Integer inum = 3; //Assigning int to Integer: Autoboxing
Long lnum = 32L; //Assigning long to Long: Autoboxing
ArrayList<Integer> arrayList = new ArrayList<Integer>();
arrayList.add(11); //Autoboxing - int primitive to Integer
arrayList.add(22); //Autoboxing

Unboxing

class UnboxingExample1
{
public static void myMethod(int num){
System.out.println(num);
}
public static void main(String[] args) {

Integer inum = new Integer(100);

/* passed Integer wrapper class object, it
* would be converted to int primitive type
* at Runtime
*/
myMethod(inum);
}
}
100
Integer inum = new Integer(5);
int num = inum; //unboxing object to primitive conversion
ArrayList arrayList = new ArrayList()
int num = arrayList.get(0); // unboxing because get method returns an Integer object

What happens behind the scenes?

Integer number = 100;
Integer number = Integer.valueOf(100);
Integer num2 = new Integer(50);
int inum = num2;
Integer num2 = new Integer(50);
int inum = num2.intValue();

Few things you should take care:

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