What is AutoBoxing and UnBoxing in java 5?

Answer 1

Conversion of primitive data types automatically to their corresponding wrapper classes is called AutoBoxing and the reverse of this operation is called UnBoxing.

Ex:

Long L = new Long(100);

long x = L;

Now x will have a value 100.

Answer 2

New to Java 5 is a feature known variously as: autoboxing, auto-unboxing, boxing, and unboxing. We'll stick with the terms boxing and unboxing. Boxing and unboxing make using wrapper classes more convenient. In the old, pre-Java 5 days, if you wanted to make a wrapper, unwrap it, use it, and then rewrap it, you might do something like this:

Integer y = new Integer(111);

int x = y.intValue();

x++;

y = new Integer(x);

System.out.println("y = " + y);

Now, with new and improved Java 5 you can say

Integer y = new Integer(111);

y++;

System.out.println("y = " + y);

Both examples produce the same output:

y = 112

And yes, you read that correctly. The code appears to be using the postincrement operator on an object reference variable! But it's simply a convenience. Behind the Scenes, the compiler does the unboxing and reassignment for you.

Note: When == is used to compare a primitive to a wrapper, the wrapper will be unwrapped and the comparison will be primitive to primitive