Increment a Integer's int value?

Question

How do I increment a Integer's value in Java? I know I can get the value with intValue, and I can set it with new Integer(int i).

playerID.intValue()++;

does not seem to work.

Note: PlayerID is a Integer that has been created with:

Integer playerID = new Integer(1);

Answer 1

Integer objects are immutable, so you cannot modify the value once they have been created. You will need to create a new Integer and replace the existing one.

playerID = new Integer(playerID.intValue() + 1);

Answer 2

Integer objects are immutable. You can't change the value of the integer held by the object itself, but you can just create a new Integer object to hold the result:

Integer start = new Integer(5);
Integer end = start + 5; // end == 10;

Answer 3

You can use IntHolder as mutable alternative to Integer. But does it worth?

Answer 4

As Grodriguez says, Integer objects are immutable. The problem here is that you're trying to increment the int value of the player ID rather than the ID itself. In Java 5+, you can just write playerID++.

As a side note, never ever call Integer's constructor. Take advantage of autoboxing by just assigning ints to Integers directly, like Integer foo = 5. This will use Integer.valueOf(int) transparently, which is superior to the constructor because it doesn't always have to create a new object.