what is difference between integer a = 5 and new Integer(5)?

Question

if i write below code(in java):

Integer a =new Integer(5);
Integer b=new Integer(5);
if(a==b){
  System.out.println(\"In ==\");
}
if(a.equals(b)){
 System.o         


        

Answer 1

In Java, you should never use the new Integer, even though it is valid syntax it is not the best way to declare integers as you have found out. Use instead Integer.valueOf(int) This has multiple advantages.

You are not creating extra objects needlessly. Whenever you use the new operator you are forcing the vm to create a new object which is not needed in most cases. valueOf(int) will return a cached copy. Since Integer objects are immutable this works great. This means that you can use == though in practice you should use a null safe compare like in Apache ObjectUtils

The == operator tests for equality. References are only equal when they refer to the same object in memory. equals method ensures 2 object instances are 'equivalent' to each other.

Integer a = new Integer(5);
Integer b = a;

a == b; // true!
a.equals(b); // true
b = new Integer(5);
a == b; // false
a.equals(b); // true

Primitives are equal whenever their value is the same.

int a = 5; int b = a;
a == b;  // true!