How to increment AtomicInteger twice?

Question

I need to increment AtomicInteger twice, like: ++i; ++i; By the endless ciycle, i want to increment counter twice and check it on the parity. But i'm always getting the variable which was incremented once. How to fix it?

the question is not complete, add some code here to explain your question. — S Jayesh, May 10 '17 at 11:46
public int increment() { atomic.incrementAndGet(); atomic.incrementAndGet(); System.out.println(atomic.get()); return atomic.get(); } — Илья Александрович, May 10 '17 at 11:54
Your code works for me. How about we see all your code? And add it to the question, not as a comment. — Steve Smith, May 10 '17 at 11:59

score 13 · Answer 1 · answered May 10 '17 at 11:55

13

    AtomicInteger counter = new AtomicInteger(100);
    counter.addAndGet(2);
    System.out.println(counter);

or

    AtomicInteger counter = new AtomicInteger(100);        
    counter.incrementAndGet();
    counter.incrementAndGet();
    System.out.println(counter);

answered May 10 '17 at 11:55

Eritrean

15,851
3
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run it in the endless cycle and check it`s parity. – Илья Александрович May 10 '17 at 12:05
@ИльяАлександрович It works. Even if you put the incrementAndGet part into an infinite loop it still works. Did you put the initialization of the AtomicInteger (`final AtomicInteger counter = new AtomicInteger(100);`) into a loop as well by any chance? – OH GOD SPIDERS May 10 '17 at 12:10
No. I put it to the another class. – Илья Александрович May 10 '17 at 12:18

score 3 · Answer 2 · answered May 10 '17 at 12:14

3

Gives me an even number every time:

import java.util.concurrent.atomic.AtomicInteger;

public class HelloWorld {
  public static void main(String[] args) {
        AtomicInteger counter = new AtomicInteger(100);
        int limit = 100;
        while ( limit-- != 0 ){
            counter.incrementAndGet();
            counter.incrementAndGet();
            System.out.println(counter.get());
        }
  }
}

answered May 10 '17 at 12:14

didiz

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I suppose there aren't, unless atomic guarantees that stuff won't be optimized away, or something esoteric like that. http://stackoverflow.com/questions/9749746/what-is-the-difference-between-atomic-volatile-synchronized – didiz May 10 '17 at 12:16
2

AFAIK the point of atomics is in case another thread changes a value. If you've only got one thread, there's no reason to use them. – Steve Smith May 10 '17 at 12:49

How to increment AtomicInteger twice?

2 Answers2