Class AtomicReference

classpath/java/util/concurrent/atomic/AtomicReference.java:17–75

import sun.misc.Unsafe;

public class AtomicReference<T> implements java.io.Serializable {
  private static final long serialVersionUID = -1848883965231344442L;
  
  private static final Unsafe unsafe = Unsafe.getUnsafe();
  private static final long valueOffset;
  
  static {
    try {
      Field<?> f = AtomicReference.class.getDeclaredField("value");
      valueOffset = unsafe.objectFieldOffset(f);
    } catch (NoSuchFieldException e) {
      throw new Error(e);
    }
  }
  
  private volatile T value;
  
  public AtomicReference() {
    this(null);
  }
  
  public AtomicReference(T initialValue) {
    this.value = initialValue;
  }
  
  public T get() {
    return value;
  }
  
  public void set(T newValue) {
    value = newValue;
  }
  
  public void lazySet(T newValue) {
    unsafe.putOrderedObject(this, valueOffset, newValue);
  }
  
  public boolean compareAndSet(T expect, T update) {
    return unsafe.compareAndSwapObject(this, valueOffset, expect, update);
  }
  
  public boolean weakCompareAndSet(T expect, T update) {
    return unsafe.compareAndSwapObject(this, valueOffset, expect, update);
  }
  
  public final T getAndSet(T newValue) {
    while (true) {
      T current = value;
      if (compareAndSet(current, newValue)) {
        return current;
      }
    }
  }
  
  @Override
  public String toString() {
    return String.valueOf(value);
  }