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

User · Accepted Answer

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

User · Answer

AtomicInteger  Maybe this is of some worth also  there is a Java class called AtomicInteger   This class has some useful methods like addAndGet int delta  or incrementAndGet    and their counterparts  which allow you to increment decrement the value of the same instance  Though the class is designed to be used in the context of concurrency  it s also quite useful in other scenarios and probably fits your need   final AtomicInteger count   new AtomicInteger  0         count incrementAndGet        Ignoring the return value

User · Answer

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

User · Answer

All the primitive wrapper objects are immutable   I m maybe late to the question but I want to add and clarify that when you do playerID    what really happens is something like this   playerID   Integer valueOf  playerID intValue     1     Integer valueOf int  will always cache values in the range -128 to 127  inclusive  and may cache other values outside of this range

User · Answer

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

User · Answer

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

User · Answer

Maybe you can try   final AtomicInteger i   new AtomicInteger 0   i set 1   i get

User · Answer

Java 7 and 8  Increment DOES change the reference  so it references to another Integer object  Look    Test public void incInteger         Integer i   5      Integer iOrig   i        i     Same as i   i   1      Assert assertEquals 6  i intValue         Assert assertNotEquals iOrig  i       Integer by itself is still immutable

User · Answer

For Java 7  increment operator      works on Integers  Below is a tested example      Integer i   new Integer  12        System out println i     12     i   i        System out println i     13

[java] Increment a Integer's int value?

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