java.util.concurrent.atomic.AtomicLong
jdk1.6类 java.util.concurrent.atomic.AtomicLong
java.util.concurrent.atomic.AtomicLong
- private static native boolean VMSupportsCS8()
- public AtomicLong(long initialValue)
- public AtomicLong()
- public final long get()
- public final void set(long newValue)
- public final void lazySet(long newValue)
- public final long getAndSet(long newValue)
- public final boolean compareAndSet(long expect, long update)
- public final boolean weakCompareAndSet(long expect, long update)
- public final long getAndIncrement()
- public final long getAndDecrement()
- public final long getAndAdd(long delta)
- public final long incrementAndGet()
- public final long decrementAndGet()
- public final long addAndGet(long delta)
- public String toString()
- public int intValue()
- public long longValue()
- public float floatValue()
- public double doubleValue()
/*
* %W% %E%
*
* Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.util.concurrent.atomic;
import sun.misc.Unsafe;
/**
* A {@code long} value that may be updated atomically. See the
* {@link java.util.concurrent.atomic} package specification for
* description of the properties of atomic variables. An
* {@code AtomicLong} is used in applications such as atomically
* incremented sequence numbers, and cannot be used as a replacement
* for a {@link java.lang.Long}. However, this class does extend
* {@code Number} to allow uniform access by tools and utilities that
* deal with numerically-based classes.
*
* @since 1.5
* @author Doug Lea
*/
/**
* 可以用原子方式更新的 long 值。有关原子变量属性的描述，
* 请参阅 java.util.concurrent.atomic 包规范。AtomicLong 可用在应用程序中
* （如以原子方式增加的序列号），并且不能用于替换 Long。但是，此类确实扩展了 Number，
* 允许那些处理基于数字类的工具和实用工具进行统一访问。
*/
public class AtomicLong extends Number implements java.io.Serializable {
private static final long serialVersionUID = 1927816293512124184L;
// setup to use Unsafe.compareAndSwapLong for updates
private static final Unsafe unsafe = Unsafe.getUnsafe();
private static final long valueOffset;
/**
* Records whether the underlying JVM supports lockless
* CompareAndSet for longs. While the unsafe.CompareAndSetLong
* method works in either case, some constructions should be
* handled at Java level to avoid locking user-visible locks.
*/
static final boolean VM_SUPPORTS_LONG_CAS = VMSupportsCS8();
/**
* Returns whether underlying JVM supports lockless CompareAndSet
* for longs. Called only once and cached in VM_SUPPORTS_LONG_CAS.
*/
private static native boolean VMSupportsCS8();
static {
try {
valueOffset = unsafe.objectFieldOffset
(AtomicLong.class.getDeclaredField("value"));
} catch (Exception ex) { throw new Error(ex); }
}
private volatile long value;
/**
* Creates a new AtomicLong with the given initial value.
*
* @param initialValue the initial value
*/
/**
* 创建具有给定初始值的新 AtomicLong。
* @param initialValue 初始值
*/
public AtomicLong(long initialValue) {
value = initialValue;
}
/**
* Creates a new AtomicLong with initial value {@code 0}.
*/
/**
* 创建具有初始值 0 的新 AtomicLong。
*/
public AtomicLong() {
}
/**
* Gets the current value.
*
* @return the current value
*/
/**
* 获取当前值。
* @return 当前值
*/
public final long get() {
return value;
}
/**
* Sets to the given value.
*
* @param newValue the new value
*/
/**
* 设置为给定值。
* @param newValue 新值
*/
public final void set(long newValue) {
value = newValue;
}
/**
* Eventually sets to the given value.
*
* @param newValue the new value
* @since 1.6
*/
/**
* 最后设置为给定值。
* @param newValue 新值
*/
public final void lazySet(long newValue) {
unsafe.putOrderedLong(this, valueOffset, newValue);
}
/**
* Atomically sets to the given value and returns the old value.
*
* @param newValue the new value
* @return the previous value
*/
/**
* 以原子方式设置为给定值，并返回旧值。
* @param newValue 新值
* @return 以前的值
*/
public final long getAndSet(long newValue) {
while (true) {
long current = get();
if (compareAndSet(current, newValue))
return current;
}
}
/**
* 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.
*/
/**
* 如果当前值 == 预期值，则以原子方式将该值设置为给定的更新值。
* @param expect 预期值
* @param update 新值
* @return 如果成功，则返回 true。返回 false 指示实际值与预期值不相等。
*/
public final boolean compareAndSet(long expect, long update) {
return unsafe.compareAndSwapLong(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.
*/
/**
* 如果当前值 == 预期值，则以原子方式将该值设置为给定的更新值。
* 可能意外失败并且不提供排序保证，所以只能在很少的情况下对 compareAndSet 进行适当地选择。
* @param expect 预期值
* @param update 新值
* @return 如果成功，则返回 true。
*/
public final boolean weakCompareAndSet(long expect, long update) {
return unsafe.compareAndSwapLong(this, valueOffset, expect, update);
}
/**
* Atomically increments by one the current value.
*
* @return the previous value
*/
/**
* 以原子方式将当前值加 1。
* @return 以前的值
*/
public final long getAndIncrement() {
while (true) {
long current = get();
long next = current + 1;
if (compareAndSet(current, next))
return current;
}
}
/**
* Atomically decrements by one the current value.
*
* @return the previous value
*/
/**
* 以原子方式将当前值减 1。
* @return 以前的值
*/
public final long getAndDecrement() {
while (true) {
long current = get();
long next = current - 1;
if (compareAndSet(current, next))
return current;
}
}
/**
* Atomically adds the given value to the current value.
*
* @param delta the value to add
* @return the previous value
*/
/**
* 以原子方式将给定值添加到当前值。
* @param delta 要添加的值
* @return 以前的值
*/
public final long getAndAdd(long delta) {
while (true) {
long current = get();
long next = current + delta;
if (compareAndSet(current, next))
return current;
}
}
/**
* Atomically increments by one the current value.
*
* @return the updated value
*/
/**
* 以原子方式将当前值加 1。
* @return 更新的值
*/
public final long incrementAndGet() {
for (;;) {
long current = get();
long next = current + 1;
if (compareAndSet(current, next))
return next;
}
}
/**
* Atomically decrements by one the current value.
*
* @return the updated value
*/
/**
* 以原子方式将当前值减 1。
* @return 更新的值
*/
public final long decrementAndGet() {
for (;;) {
long current = get();
long next = current - 1;
if (compareAndSet(current, next))
return next;
}
}
/**
* Atomically adds the given value to the current value.
*
* @param delta the value to add
* @return the updated value
*/
/**
* 以原子方式将给定值添加到当前值。
* @param delta 要添加的值
* @return 更新的值
*/
public final long addAndGet(long delta) {
for (;;) {
long current = get();
long next = current + delta;
if (compareAndSet(current, next))
return next;
}
}
/**
* Returns the String representation of the current value.
* @return the String representation of the current value.
*/
/**
* 返回当前值的字符串表示形式。
* @return 当前值的字符串表示形式。
*/
public String toString() {
return Long.toString(get());
}
/**
* 从类 Number 复制的描述
* 以 int 形式返回指定的数值。这可能会涉及到舍入或取整。
*/
public int intValue() {
return (int)get();
}
/**
* 从类 Number 复制的描述
* 以 long 形式返回指定的数值。这可能涉及到舍入或取整。
*/
public long longValue() {
return (long)get();
}
/**
* 从类 Number 复制的描述
* 以 float 形式返回指定的数值。这可能会涉及到舍入。
*/
public float floatValue() {
return (float)get();
}
/**
* 从类 Number 复制的描述
* 以 double 形式返回指定的数值。这可能会涉及到舍入。
*/
public double doubleValue() {
return (double)get();
}
}