Java synchronized可以修饰 synchronized修饰方法和代码块

public class Thread1 implements Runnable { 
     public void run() { 
          synchronized(this) { 
               for (int i = 0; i < 5; i++) { 
                    System.out.println(Thread.currentThread().getName() + " synchronized loop " + i); 
               } 
          } 
     } 
     public static void main(String[] args) { 
          Thread1 t1 = new Thread1(); 
          Thread ta = new Thread(t1, "A"); 
          Thread tb = new Thread(t1, "B"); 
          ta.start(); 
          tb.start(); 
     }
}
public class Thread2 {
     public void m4t1() { 
          synchronized(this) { 
               int i = 5; 
               while( i-- > 0) { 
                    System.out.println(Thread.currentThread().getName() + "_synchronized"+" : " + i);
                    try { 
                         Thread.sleep(500); 
                    } catch (InterruptedException ie) { 
                    } 
               } 
          } 
     } 
     public void m4t2() { 
          int i = 5; 
          while( i-- > 0) { 
               System.out.println(Thread.currentThread().getName() + " : " + i); 
               try { 
                    Thread.sleep(500); 
               } catch (InterruptedException ie) { 
               } 
          } 
     } 
     public static void main(String[] args) { 
          final Thread2 myt2 = new Thread2(); 
          Thread t1 = new Thread(  new Runnable() {  public void run() {  myt2.m4t1();  }  }, "t1"  );
          //java多线程实际上是实现了run()方法的多线程，所以构造器里面只要构造他的run()方法即可
          Thread t2 = new Thread(  new Runnable() {  public void run() { myt2.m4t2();   }  }, "t2"  ); 
          t1.start(); 
          t2.start(); 
     }
}
public class Thread2 {
     public void m4t1() { 
          synchronized(this) { 
               int i = 5; 
               while( i-- > 0) { 
                    System.out.println(Thread.currentThread().getName() + "_synchronized"+" : " + i);
                    try { 
                         Thread.sleep(500); 
                    } catch (InterruptedException ie) { 
                    } 
               } 
          } 
     } 
     public void m4t2() {
          //其实 synchronized 全用来修饰代码块也可以，把方法的所有代码都包进去就相当于修饰方法（作用上）
          synchronized(this) {
               int i = 5;
               while (i-- > 0) {
                    System.out.println(Thread.currentThread().getName() + " : " + i);
                    try {
                         Thread.sleep(500);
                    } catch (InterruptedException ie) {
                    }
               }
          }
     } 
     public static void main(String[] args) { 
          final Thread2 myt2 = new Thread2(); 
          Thread t1 = new Thread(  new Runnable() {  public void run() {  myt2.m4t1();  }  }, "t1"  );
          //java多线程实际上是实现了run()方法的多线程，所以构造器里面只要构造他的run()方法即可
          Thread t2 = new Thread(  new Runnable() {  public void run() { myt2.m4t2();   }  }, "t2"  ); 
          t1.start(); 
          t2.start(); 
     }
}
//修改Thread2.m4t2()方法如下
     public synchronized void m4t2() { 
//synchronized 修饰方法同样会锁住方法的对象
          int i = 5; 
          while( i-- > 0) { 
               System.out.println(Thread.currentThread().getName() + " : " + i); 
               try { 
                    Thread.sleep(500); //睡，就是让他切换线程
               } catch (InterruptedException ie) { 
               } 
          } 
     }
public class Thread2 {
     public synchronized void m4t1() {
//          synchronized(this) {
               int i = 5; 
               while( i-- > 0) { 
                    System.out.println(Thread.currentThread().getName() + "_synchronized"+" : " + i);
                    try { 
                         Thread.sleep(500); 
                    } catch (InterruptedException ie) { 
                    } 
               } 
//          }
     } 
     public synchronized void m4t2() {
          //其实 synchronized 全用来修饰代码块也可以，把方法的所有代码都包进去就相当于修饰方法（作用上）
//          synchronized(this) {
               int i = 5;
               while (i-- > 0) {
                    System.out.println(Thread.currentThread().getName() + " : " + i);
                    try {
                         Thread.sleep(500);
                    } catch (InterruptedException ie) {
                    }
               }
//          }
     } 
     public static void main(String[] args) { 
          final Thread2 myt2 = new Thread2(); 
          Thread t1 = new Thread(  new Runnable() {  public void run() {  myt2.m4t1();  }  }, "t1"  );
          //java多线程实际上是实现了run()方法的多线程，所以构造器里面只要构造他的run()方法即可
          Thread t2 = new Thread(  new Runnable() {  public void run() { myt2.m4t2();   }  }, "t2"  ); 
          t1.start(); 
          t2.start(); 
     }
}
public class Thread3 {
     class Inner {
          private  void m4t1() {
               int i = 5;
               while(i-- > 0) {
                    System.out.println(Thread.currentThread().getName() + " : Inner.m4t1()=" + i);
                    try {
                         Thread.sleep(500);
                    } catch(InterruptedException ie) {
                    }
               }
          }
          private  void m4t2() {
               int i = 5;
               while(i-- > 0) {
                    System.out.println(Thread.currentThread().getName() + " : Inner.m4t2()=" + i);
                    try {
                         Thread.sleep(500);
                    } catch(InterruptedException ie) {
                    }
               }
          }
     }
     private void m4t1(Inner inner) {
          synchronized (inner) { //使用对象锁
               inner.m4t1();
          }
     }
 
     private void m4t2(Inner inner) {
          inner.m4t2();
     }
    
     public static void main(String[] args) {
          final Thread3 myt3 = new Thread3();
          final Inner inner = myt3.new Inner();
          final Inner inner1 = myt3.new Inner();
          Thread t1 = new Thread( new Runnable() {public void run() { myt3.m4t1(inner);} }, "t1");
     Thread t2 = new Thread( new Runnable() {public void run() { myt3.m4t2(inner);} }, "t2");
     t1.start();
     t2.start();
  }
}
private synchronized void m4t2() { 
          int i = 5; 
          while(i-- > 0) { 
               System.out.println(Thread.currentThread().getName() + " : Inner.m4t2()=" + i); 
               try { 
                    Thread.sleep(500); 
               } catch(InterruptedException ie) { 
               } 
          } 
     }