Java多线程编程中线程锁与读写锁的使用示例

线程锁Lock
Lock  相当于 当前对象的 Synchronized

import java.util.concurrent.locks.Lock; 
import java.util.concurrent.locks.ReentrantLock; 
 
public class LockTest { 
  public static void main(String[] args) { 
    final Outer outer = new LockTest().new Outer(); 
    new Thread(new Runnable() { 
 
      @Override 
      public void run() { 
 // TODO Auto-generated method stub 
 while (true) { 
   outer.out1("zhangxiaoxiao"); 
   outer.out2("lihuoming"); 
 } 
      } 
 
    }).start(); 
    new Thread(new Runnable() { 
 
      @Override 
      public void run() { 
 // TODO Auto-generated method stub 
 while (true) { 
   outer.out1("zhangxiaoxiao"); 
   outer.out2("lihuoming"); 
 } 
      } 
 
    }).start(); 
 
  } 
  class Outer { 
    Lock lock = new ReentrantLock(); 
    void out1(String name) { 
      lock.lock(); 
      int len = name.length(); 
      for (int i = 0; i < len; i++) { 
 System.out.print(name.charAt(i)); 
      } 
      System.out.println(); 
      lock.unlock(); 
    } 
    void out2(String name) { 
      lock.lock(); 
      int len = name.length(); 
      for (int i = 0; i < len; i++) { 
 System.out.print(name.charAt(i)); 
      } 
      System.out.println(); 
      lock.unlock(); 
    } 
  } 
} 

读写锁 ReentrantReadWriteLock

 读写锁：允许多条线程同时读；不能读中有写；不能写中有读；不能写中有写

import java.util.HashMap; 
import java.util.Map; 
import java.util.concurrent.locks.ReadWriteLock; 
import java.util.concurrent.locks.ReentrantReadWriteLock; 
 
public class ReadWriteLockTest2 { 
  private Map data = new HashMap(); 
  private ReadWriteLock lock = new ReentrantReadWriteLock();  
  //读写锁 
  public Object getInstance1(String key, Object obj) { 
    lock.readLock().lock(); 
    Object value = null; 
    try { 
      value = data.get(key); 
      if (value == null) {//一条线程进入这里， 
 lock.readLock().unlock();//读锁解了，其他线程就可能也到这了 
 lock.writeLock().lock();//只能有一条线程到这，写锁开启，要写入数据了 
 if (data.get(key) == null) { 
   value = obj;   
         
   data.put(key, value);  
 } 
 lock.writeLock().unlock();//写完了，解锁 
 lock.readLock().lock(); 
      } 
    } finally { 
      lock.readLock().unlock(); 
    }   
    return value; 
  }