[Java多线程]-J.U.C.atomic包下的AtomicInteger，AtomicLong等类的源码解析

一、Atomic包下的所有类如下表：

boolean

int

int

volatileint

long

long

volatilelong

AtomicMarkableReference

volatile

AtomicStampedReference

二、AtomicInteger源码分析和基本的方法使用:

AtomicInteger()

0

AtomicInteger(int initialValue)

int

addAndGet(int delta)

boolean

compareAndSet(int expect,int update)

==

int

decrementAndGet()

double

doubleValue()

double

float

floatValue()

float

int

get()

int

getAndAdd(int delta)

int

getAndDecrement()

int

getAndIncrement()

int

getAndSet(int newValue)

int

incrementAndGet()

int

intValue()

int

void

lazySet(int newValue)

long

longValue()

long

void

set(int newValue)

String

toString()

boolean

weakCompareAndSet(int expect,int update)

==

byteValue, shortValue

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

/**
* An object reference that may be updated atomically. See the {@link
* java.util.concurrent.atomic} package specification for description
* of the properties of atomic variables.
* @since 1.5
* @author Doug Lea
* @param <V> The type of object referred to by this reference
*/
public class AtomicReference<V>  implements java.io.Serializable {
private static finallong serialVersionUID = -1848883965231344442L;

private static final Unsafe unsafe = Unsafe.getUnsafe();
private static finallong valueOffset;

static {
try {
valueOffset = unsafe.objectFieldOffset
(AtomicReference.class.getDeclaredField("value"));
} catch (Exception ex) { throw new Error(ex); }
}

private volatile V value;

/**
* Creates a new AtomicReference with the given initial value.
*
* @param initialValue the initial value
*/
public AtomicReference(V initialValue) {
value = initialValue;
}

/**
* Creates a new AtomicReference with null initial value.
*/
public AtomicReference() {
}

/**
* Gets the current value.
*
* @return the current value
*/
public final V get() {
return value;
}

/**
* Sets to the given value.
*
* @param newValue the new value
*/
public finalvoid set(V newValue) {
value = newValue;
}

/**
* Eventually sets to the given value.
*
* @param newValue the new value
* @since 1.6
*/
public finalvoid lazySet(V newValue) {
unsafe.putOrderedObject(this, valueOffset, newValue);
}

/**
* Atomically sets the value to the given updated value
* if the current value {@code ==} the expected value.
* @param expect the expected value
* @param update the new value
* @return true if successful. False return indicates that
* the actual value was not equal to the expected value.
*/
public finalboolean compareAndSet(V expect, V update) {
return unsafe.compareAndSwapObject(this, valueOffset, expect, update);
}

/**
* Atomically sets the value to the given updated value
* if the current value {@code ==} the expected value.
*
* <p>May <a href="package-summary.html#Spurious">fail spuriously</a>
* and does not provide ordering guarantees, so is only rarely an
* appropriate alternative to {@code compareAndSet}.
*
* @param expect the expected value
* @param update the new value
* @return true if successful.
*/
public finalboolean weakCompareAndSet(V expect, V update) {
return unsafe.compareAndSwapObject(this, valueOffset, expect, update);
}

/**
* Atomically sets to the given value and returns the old value.
*
* @param newValue the new value
* @return the previous value
*/
public final V getAndSet(V newValue) {
while (true) {
V x = get();
if (compareAndSet(x, newValue))
return x;
}
}

/**
* Returns the String representation of the current value.
* @return the String representation of the current value.
*/
public String toString() {
return String.valueOf(get());
}

}

import java.util.concurrent.atomic.AtomicReference;

public class AtomTest {
private static AtomicReference<Pig> pigtest;
public staticvoid main(String[] args) {
Pig pig = new Pig("猪坚强", 2);
Pig pig2 = new Pig("猪八戒", 2);
System.out.println("pig_hashCode:"+pig.hashCode());
System.out.println("pig2_hashCode:"+pig2.hashCode());
AtomTest.pigtest = new AtomicReference<Pig>(pig);
System.out.println(pigtest.get().toString());
System.out.println(pigtest.get().hashCode());
System.out.println(pigtest.compareAndSet(pig, pig2));
System.out.println(pigtest.compareAndSet(pig, pig2));
System.out.println(pigtest.get().toString());
System.out.println(pigtest.get().hashCode());
}
}

pig_hashCode:779824645
pig2_hashCode:420110874
[猪坚强,2]
779824645
true
false
[猪八戒,2]
420110874

五、总结：