java多线程与线程同步

 

             JAVA 线程同步的几种方式

 

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class SynTest {

 public static void main(String[] args) throws Exception{
  //1.两个线程共享变量，变量值不确定
  //nonsyn();
  //2.使用线程同步方法：synchronized save1
  //syn();
  //3.使用volatile 线程同步: volatile int account
  //vola();
  //4.使用重入锁ReentrantLock: save2() , new lock
  //lock();
  //5.使用局部变量ThreadLocal线程同步： ThreadLocal<int>
  Bank2 b=new Bank2();
  NewThread2 t=new NewThread2(b);
  
  Thread t1=new Thread(t,"t1");
  t1.start();
  Thread t2=new Thread(t,"t2");
  t2.start();
  
  
  t1.join();
  t2.join();
  System.out.println("非同步  account="+b.get());
 }

 static void nonsyn()throws Exception{
  Bank b=new Bank();
  NewThread t=new NewThread(b);
  
  Thread t1=new Thread(t,"t1");
  t1.start();
  Thread t2=new Thread(t,"t2");
  t2.start();
  
  
  t1.join();
  t2.join();
  System.out.println("非同步  account="+b.get());
 }
 
 static void syn()throws Exception{
  Bank b=new Bank();
  NewThread t=new NewThread(b);
  
  Thread t1=new Thread(t,"t1");
  t1.start();
  Thread t2=new Thread(t,"t2");
  t2.start();
  
  
  t1.join();
  t2.join();
  System.out.println("非同步  account="+b.get());
 }
 
 static void vola()throws Exception{
  Bank b=new Bank();
  NewThread t=new NewThread(b);
  
  Thread t1=new Thread(t,"t1");
  t1.start();
  Thread t2=new Thread(t,"t2");
  t2.start();
  
  
  t1.join();
  t2.join();
  System.out.println("非同步  account="+b.get());
 }
 
 static void lock()throws Exception{
  Bank b=new Bank();
  NewThread t=new NewThread(b);
  
  Thread t1=new Thread(t,"t1");
  t1.start();
  Thread t2=new Thread(t,"t2");
  t2.start();
  
  
  t1.join();
  t2.join();
  System.out.println("非同步  account="+b.get());
 }
}

class Bank{
 private int account;
 //private volatile int account;
 
 private Lock lock=new ReentrantLock();
 
 public void save(int money){
  this.account+=money;
 }
 
// public synchronized void save1(int money){
//  this.account+=money;
// }
 
 public void save2(int money){
  lock.lock();
  this.account+=money;
  lock.unlock();
 }
 
 public int get(){
  return this.account;
 }
}

class NewThread implements Runnable{
 private Bank bank;
 
 public NewThread(Bank bank){
  this.bank=bank;
 }

 public void run() {
  
  for(int i=0;i<30000;i++){
   //bank.save(10); //使用volatile 同步
   //bank.save1(10); //使用synchronized 同步
   bank.save2(10);//使用lock同步
   System.out.println("非同步  account="+bank.get());
   
  }
  
  //System.out.println( " account="+bank.get());//结果不确定20000
  
 }
 
}

class Bank2{
 private ThreadLocal<Integer> account=new ThreadLocal<Integer>(){
 
  protected Integer initialValue(){
   return 0;
  }
 };
 public void save(int money){
  account.set(account.get()+money);
 }
 
 public int get(){
  return this.account.get();
 }
}

class NewThread2 implements Runnable{
 private Bank2 bank;
 
 public NewThread2(Bank2 bank){
  this.bank=bank;
 }

 public void run() {
  
  for(int i=0;i<30000;i++){
   bank.save(10);
   //System.out.println(Thread.currentThread().getName()+"同步  account="+bank.get());
   
  }
  System.out.println(Thread.currentThread().getName()+"同步  account="+bank.get());
 }
 
}

 

   ThreadLocal 线程局部变量如何线程通信呢？