线程同步synchronized与Lock对比

谁借莪１个温暖的怀抱￠ 2022-05-29 06:23 228阅读 0赞

1.java关键字synchronized实现线程同步

@RequestMapping(value="xctb.htm", method={RequestMethod.GET, RequestMethod.POST})
    public void xctb(HttpServletRequest request) throws Exception{      
        synchronized (this) {
            String sql = "select number from tablename where id=1";
    	List<Map> list = baseDao.getResultMap(sql);
    	if(list != null && list.size() > 0){
    	    System.out.println("总数:"+list.get(0).get("number"));
    	    Thread.sleep(1000);
    	    String s = "update tablename set number=number-1 where id=1";
    	    baseDao.executeSQL(s);
    	}
        }		
    }

2.Lock接口实现线程同步

private ReentrantLock lock = new ReentrantLock();
    @RequestMapping(value="xctb.htm", method={RequestMethod.GET, RequestMethod.POST})
    public void xctb(HttpServletRequest request) throws Exception{
        if (lock.tryLock(3, TimeUnit.SECONDS)) {
    	try {
    	    String sql = "select number from tablename where id=1";
    	    List<Map> list = baseDao.getResultMap(sql);
    	    if(list != null && list.size() > 0){
    	        System.out.println("总数:"+list.get(0).get("number"));
    		Thread.sleep(1000);
    		String s = "update tablename set number=number-1 where id=1";
    		baseDao.executeSQL(s);
    	    }
    	}catch(Exception e){
    	    e.printStackTrace();
    	} finally {
    	    lock.unlock();
        }else{
            System.out.println("3秒内没有获得锁");
        }
    }

总结：synchronized适合少量线程并发，Lock适合大量线程并发，另ReentrantLock可设置锁的获取时间，使用起来相对灵活。