TransactionalDataStructure

import java.util.concurrent.atomic.AtomicReference;
 
public abstract class Helper {
 
    private static final class Data {
 
        final int value1;
        final int value2;
        final int value3;
 
        Data(int value1, int value2, int value3) {
            this.value1 = value1;
            this.value2 = value2;
            this.value3 = value3;
        }
    }
 
    private final AtomicReference<Data> data = new AtomicReference<>(new Data(0, 0, 0));
 
    protected abstract int combine(int x, int y);
 
    public final void update() {
        Data current;
        while (true) {
            current = data.get();
 
            // the following three operations must be performed in a "transaction" ...
            int v1 = combine(current.value1, current.value2);
            int v2 = combine(current.value2, current.value3);
            int v3 = combine(current.value3, current.value1);
            // either we want to apply them all or none at all!
 
            if (data.compareAndSet(current, new Data(v1, v2, v3))) {
                // CAS checks the value in data is still == to current
                // if so it changes it to new Data and we can return
                return;
            }
            // otherwise try again
        }
    }
}