Object obj = new Object(); 
... 
synchronized(obj) { 
 //TODO: 访问临界资源 
} 

private volatile Boolean isTrue = false; 
 
publich void aMethod() { 
 ... 
 synchronized(isTrue) { 
  isTrue = !isTrue; 
  //TODO: 访问临界资源 
  isTrue = !isTrue; 
 } 
 ... 
} 

public class BooleanTest { 
   
  private volatile Boolean isTrue = Boolean.FALSE; //此处用false也一样 
   
  public void aMethod() { 
    for(int i=0;i<10;i++) { 
      Thread t = new Thread() { 
        public void run() { 
          synchronized(isTrue) { 
            isTrue = !isTrue; 
            System.out.println(Thread.currentThread().getName() + " - isTrue=" + isTrue); 
            try{ 
              Double ran = 1000 * Math.random(); 
              Thread.sleep(ran.intValue()); 
            }catch(InterruptedException e) {} 
             
            if(!isTrue) System.out.println(Thread.currentThread().getName() + " - Oh, No!"); 
 
            isTrue = !isTrue; 
          } 
        } 
      }; 
      t.start(); 
    } 
  } 
   
  public static void main(String... args) { 
    BooleanTest bt = new BooleanTest(); 
    bt.aMethod(); 
  } 
} 

private volatile Boolean aBoolean = Boolean.FALSE; 
 
private volatile Boolean anotherBoolean = false; 
 
public void aMethod() { 
 ... 
 synchronized(aBoolean) { 
  //TODO: 访问临界资源1 
 } 
 ... 
} 
 
public void anotherMethod() { 
 ... 
 synchronized(anotherBoolean) { 
  //TODO: 访问临界资源2 
 } 
 ... 
}