Java那些事儿之线程安全

@线程：

线程安全：所谓的线程安全，就是要控制多个线程对某个资源的有序访问和修改。
保证线程安全的方法：
1.synchronized关键字用于修饰方法体或者包裹代码快，保证在多线程环境下，未返回结果前只能够被一个线程操作。

       public synchronized void count（）｛
	｝
	synchronized（lock）｛
	代码块
	｝

         public volatile num = 0;

	Lock lock = new ReentrantLock();
	public void count（）｛
	    lock.lock();//取得锁
	    代码块
	    lock.unlock();
	｝

int num = 0;
for（int i = 0;i<10;i++）｛
   num+=1;
｝

package com.zhaofeng;

public class Bank {  
	  
    private int balance;  
  
    public Bank(int balance) {  
        this.balance = balance;  
    }  
  
    public int getBalance() {  
        return balance;  
    }  
  
    public void add(int num) {  
        balance = balance + num;  
    }  
  
    public void out(int num) {  
        balance = balance - num;  
    }  
  
    public static void main(String[] args) throws InterruptedException {  
        Bank account = new Bank(1000);  
        Thread a = new Thread(new AddThread(account, 20000), "存款");  
        Thread b = new Thread(new OutThread(account, 10000), "取款");  
        a.start();  
        b.start();  
        a.join();  
        b.join();  
        System.out.println(account.getBalance());  
    }  
  
    static class AddThread implements Runnable {  
        Bank account;  
        int     amount;  
  
        public AddThread(Bank account, int amount) {  
            this.account = account;  
            this.amount = amount;  
        }  
  
        public void run() {  
            for (int i = 0; i < amount; i++) {  
                account.add(1);  
            }  
        }  
    }  
  
    static class OutThread implements Runnable {  
        Bank account;  
        int     amount;  
  
        public OutThread(Bank account, int amount) {  
            this.account = account;  
            this.amount = amount;  
        }  
  
        public void run() {  
            for (int i = 0; i < amount; i++) {  
                account.out(1);  
            }  
        }  
    }  
}  

 public synchronized void add(int num) {  
        balance = balance + num;  
    }  
  
    public synchronized void out(int num) {  
        balance = balance - num;  
    }  

Java那些事儿之线程安全

原文：http://blog.csdn.net/fengfeng91/article/details/18948575