23.讀寫鎖ReadWriteLock

ReentrantReadWriteLock

    所謂的讀寫鎖，是訪問資源共享共享鎖、互斥鎖，若是對資源加了寫鎖，其餘線程沒法獲取寫鎖與讀鎖，可是持有寫鎖的線程，能夠對資源

    加讀鎖；若是一個線程對資源加了讀鎖，那麼其餘線程能夠繼續加讀鎖。讀讀共享、讀寫互斥、寫寫互斥

 
 
 
 
 

  
  
  
  
  
   
   
   
   
   

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

   
   
   
   
   
 
 
 
 
 
 
 
 
 
 

  
  
  
  
  
 
   
    
    
    
    
    

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

     
     
     
     
     

    
    
    
    
    
 
  
  
  
  
  
  
 
   
 
    
     
     
     
     
     

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

      
      
      
      
      

     
     
     
     
     
 
   
  
  
 
 
 
 
 
package dmeo9;public class MyAccount { private String oid; private int cash; public MyAccount(){ } public MyAccount(String oid, int cash) { this.oid = oid; this.cash = cash; } public String getOid() { return oid; } public void setOid(String oid) { this.oid = oid; } public int getCash() { return cash; } public void setCash(int cash) { this.cash = cash; }}package dmeo9;import java.util.concurrent.locks.ReadWriteLock;public class User implements Runnable { private String name;//用戶名 private MyAccount myAccount;//操做的帳戶 private int ioCash;//操做的金額 private ReadWriteLock readWriteLock;//讀寫鎖操做鎖須要的鎖 private boolean isCheck;//是否操做？ public User() { } public User(String name, MyAccount myAccount, int ioCash, ReadWriteLock readWriteLock, boolean isCheck) { this.name = name; this.myAccount = myAccount; this.ioCash = ioCash; this.readWriteLock = readWriteLock; this.isCheck = isCheck; } public String getName() { return name; } public void setName(String name) { this.name = name; } public MyAccount getMyAccount() { return myAccount; } public void setMyAccount(MyAccount myAccount) { this.myAccount = myAccount; } public int getIoCash() { return ioCash; } public void setIoCash(int ioCash) { this.ioCash = ioCash; } public ReadWriteLock getReadWriteLock() { return readWriteLock; } public void setReadWriteLock(ReadWriteLock readWriteLock) { this.readWriteLock = readWriteLock; } public boolean isCheck() { return isCheck; } public void setCheck(boolean check) { isCheck = check; } @Override public void run() { if (isCheck) { /*獲取讀鎖*/ try { readWriteLock.readLock().lock(); System.err.println("\n讀：" + getName() + "\t正在read 查詢\t" + getMyAccount() + "\t帳戶，當前金額爲：" + myAccount.getCash()); } catch (Exception e) { e.printStackTrace(); } finally { /*釋放讀鎖*/ readWriteLock.readLock().unlock(); } } else { /*獲取寫的鎖*/ try { readWriteLock.writeLock().lock(); System.err.println("寫：" + getName() + "\t正在write 操做\t" + getMyAccount() + "帳戶，當前金額爲：" + myAccount.getCash()); getMyAccount().setCash(getMyAccount().getCash() + getIoCash()); System.err.println("操做成功：金額爲" + getIoCash() + "\t當前金額爲：" + getMyAccount().getCash()+"\n\n"); } catch (Exception e) { e.printStackTrace(); } finally { /*釋放寫鎖*/  /** * 通常用lock或者 readwritelock時，須要把 unlock方法放在一個 fianlly 塊中，由於程序運行的時候可能會 出現一些咱們人爲控制不了的因素，致使鎖一直沒釋放，那其餘線程就進不來了. */ readWriteLock.writeLock().unlock(); } } }}package dmeo9;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.locks.ReadWriteLock;import java.util.concurrent.locks.ReentrantReadWriteLock;public class DemoReadWriteLock { public static void main(String[] args){ MyAccount myAccount = new MyAccount("工商銀行95599200901215522",160000); ReadWriteLock readWriteLock = new ReentrantReadWriteLock(false); ExecutorService executorService = Executors.newFixedThreadPool(2); User u1 = new User("張三", myAccount, -4000, readWriteLock, false); User u2 = new User("小明", myAccount, 6000, readWriteLock, false); User u3 = new User("小明", myAccount, -8000, readWriteLock, false); User u4 = new User("小明", myAccount, 800, readWriteLock, false); User u5 = new User("小明他爹", myAccount, 0, readWriteLock, true); executorService.execute(u1); executorService.execute(u2); executorService.execute(u3); executorService.execute(u4); executorService.execute(u5); /*關閉線程池*/ executorService.shutdown(); }}輸出：寫：張三 正在write 操做 dmeo9.MyAccount@1a8fdcaa帳戶，當前金額爲：160000 操做成功：金額爲-4000 當前金額爲：156000 寫：小明 正在write 操做 dmeo9.MyAccount@1a8fdcaa帳戶，當前金額爲：156000 操做成功：金額爲6000 當前金額爲：162000 寫：小明 正在write 操做 dmeo9.MyAccount@1a8fdcaa帳戶，當前金額爲：162000 操做成功：金額爲-8000 當前金額爲：154000 寫：小明 正在write 操做 dmeo9.MyAccount@1a8fdcaa帳戶，當前金額爲：154000 操做成功：金額爲800 當前金額爲：154800 讀：小明他爹 正在read 查詢 dmeo9.MyAccount@1a8fdcaa 帳戶，當前金額爲：154800