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📜  Java并发-AtomicLong类

📅  最后修改于: 2020-11-15 03:54:17             🧑  作者: Mango

java.util.concurrent.atomic.AtomicLong类提供了对基础长值的操作，这些值可以原子方式读写，并且还包含高级原子操作。 AtomicLong支持对基本long变量的原子操作。它具有get和set方法，它们的工作方式类似于对易失性变量的读写。也就是说，一个集合与该变量的任何后续get都具有事前发生的关系。原子compareAndSet方法还具有这些内存一致性功能。

原子长方法

以下是AtomicLong类中可用的重要方法的列表。

Sr.No. Method & Description
1

public long addAndGet(long delta)

Atomically adds the given value to the current value.
2

public boolean compareAndSet(long expect, long update)

Atomically sets the value to the given updated value if the current value is same as the expected value.
3

public long decrementAndGet()

Atomically decrements by one the current value.
4

public double doubleValue()

Returns the value of the specified number as a double.
5

public float floatValue()

Returns the value of the specified number as a float.
6

public long get()

Gets the current value.
7

public long getAndAdd(long delta)

Atomiclly adds the given value to the current value.
8

public long getAndDecrement()

Atomically decrements by one the current value.
9

public long getAndIncrement()

Atomically increments by one the current value.
10

public long getAndSet(long newValue)

Atomically sets to the given value and returns the old value.
11

public long incrementAndGet()

Atomically increments by one the current value.
12

public int intValue()

Returns the value of the specified number as an int.
13

public void lazySet(long newValue)

Eventually sets to the given value.
14

public long longValue()

Returns the value of the specified number as a long.
15

public void set(long newValue)

Sets to the given value.
16

public String toString()

Returns the String representation of the current value.
17

public boolean weakCompareAndSet(long expect, long update)

Atomically sets the value to the given updated value if the current value is same as the expected value.

例

以下TestThread程序显示了在基于线程的环境中使用AtomicLong安全计数器的实现。

现场演示
import java.util.concurrent.atomic.AtomicLong;

public class TestThread {

   static class Counter {
      private AtomicLong c = new AtomicLong(0);

      public void increment() {
         c.getAndIncrement();
      }

      public long value() {
         return c.get();
      }
   }

   public static void main(final String[] arguments) throws InterruptedException {
      final Counter counter = new Counter();
      
      //1000 threads
      for(int i = 0; i < 1000 ; i++) {
         
         new Thread(new Runnable() {
            
            public void run() {
               counter.increment();
            }
         }).start();    
      }
      Thread.sleep(6000);                         
      System.out.println("Final number (should be 1000): " + counter.value());
   }
}

这将产生以下结果。

输出

Final number (should be 1000): 1000