标签:mini jee junit erro err tac logs min 获取值
package com.thinkgem.jeesite.test; import org.junit.Test; import sun.misc.Unsafe; /** * Created by zhuangyan on 2016/12/8 0008. */ import java.lang.reflect.Field; import java.util.concurrent.atomic.AtomicInteger; import java.util.concurrent.atomic.AtomicLong; public class transationTest { private static String ready ="sdfassdf"; private volatile int numberValue=0; private static final Unsafe unsafe = getUnsafe(); private static final long valueOffset; private long test; static { try { //利用反射获取值地址 valueOffset = unsafe.objectFieldOffset (transationTest.class.getDeclaredField("numberValue")); } catch (Exception ex) { throw new Error(ex); } } //利用反射方式拿到 unsafe 不然会包Security错误, public static Unsafe getUnsafe() { try { Field f = Unsafe.class.getDeclaredField("theUnsafe"); f.setAccessible(true); return (Unsafe)f.get(null); } catch (Exception e) { /* ... */ return null; } } private class ReaderThread extends Thread { @Override public synchronized void run() { for(int i=1;i<=2000;i++){ System.out.println(Thread.currentThread()+ " :" + numberValue); // number = number + 1; // numberValue = numberValue + 1; casTest(1); // ttt(0); System.out.println(Thread.currentThread()+ " :" +numberValue); } } } //cast ++ public int casTest( int except){ for(;;){ int currNum = numberValue; int tmpNumber = numberValue + 1; //cas 如果currnum 等于当前值(valueOffset指定了值),则更新当前值为tmpNumber if(unsafe.compareAndSwapInt(this,valueOffset,currNum,tmpNumber)){ System.out.println(Thread.currentThread()+ " iudddfifififtmp:" + tmpNumber); return tmpNumber; } } } public void mainTest() { System.out.println("begin"); for(int i=1;i<=50;i++){ Thread Re = new ReaderThread(); Re.start(); } System.out.println("1249"); } } -------------- 测试方法代码 package com.thinkgem.jeesite.test; import org.junit.*; /** * Created by Administrator on 2017/2/19 0019. */ public class junitTest { @org.junit.Test public void Test() throws InterruptedException { System.out.println("tst"); transationTest tt = new transationTest(); tt.mainTest(); Thread.sleep(15000); }; }
利用cas来实现了一个累加多线程方法,用于理解cas原理以及unsafe方法的swap使用
自己利用unsafe的cas实现的AtomicInteger
标签:mini jee junit erro err tac logs min 获取值
原文地址:http://www.cnblogs.com/zhuangyan728/p/6417883.html