如何在多线程环境中交换布尔值? [英] How to swap boolean value in multi-threaded environment?

问题描述

1.

volatile boolean bool = false;
// ...
bool = !bool;

2.

volatile AtomicBoolean bool= new AtomicBoolean(false);
// ...
bool.set(!bool.get());

如果有多个线程正在运行，并且其中一个需要交换bool的值并使新值对于其他线程可见，那么这两种方法是否存在相同的问题，即允许在另一个线程中进行操作-在读写之间，还是AtomicBoolean是否确保在.get()和.set()的调用之间什么都不会发生?

If there are multiple threads running, and one of them needs to swap the value of bool and making the new value visible for other threads, do these 2 approaches have the same problem of allowing for another thread's operation to happen in-between the read and write, or does AtomicBoolean assure that nothing will happen in-between the call to .get() and .set()?

推荐答案

AtomicBoolean无法保证get()和set()之间不会发生任何事情.
您可以创建在同一个对象上同步的3个方法get()，set()和swap().

AtomicBoolean cannot assure nothing will happen between the get() and set().
You could create 3 methods get(), set() and swap() that synchronize on the same object.

您可以尝试这样的事情:

You could try something like this:

public class SyncBoolean
{
  public SyncBoolean()
  {
    value = false;
  }

  public synchronized boolean get()
  {
    return (value);
  }

  public synchronized void set(boolean newValue)
  {
    value = newValue;
  }

  public synchronized void swap()
  {
    value = !value;
  }

  private boolean value;

} // class SyncBoolean

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