反射、Unsafe、直接调用性能大比拼

package com.hundsun.jrescloud;

import sun.misc.Unsafe;

import java.lang.reflect.Field;

/**
 * @author zjhua
 * @description
 * @date 2020/1/26 20:20
 */
public class TestUnSafe {
    static final Unsafe unsafe;
    static final long stateOffset;
    static final long volStateOffset;
    private volatile long volState = 0;
    private long state = 0;

    static {
        try {
            Field field = Unsafe.class.getDeclaredField("theUnsafe");
            field.setAccessible(true);
            unsafe = (Unsafe) field.get(null);
            stateOffset = unsafe.objectFieldOffset(TestUnSafe.class.getDeclaredField("state"));
            volStateOffset = unsafe.objectFieldOffset(TestUnSafe.class.getDeclaredField("volState"));
        } catch (Exception ex) {
            System.out.println(ex.getLocalizedMessage());
            throw new Error(ex);
        }
    }

    public static void main(String[] args) {
        TestUnSafe test = new TestUnSafe();
        long beg = System.currentTimeMillis();
        for (int i = 0; i < 100000000; i++) {
            unsafe.putLong(test, stateOffset,i);
        }
        System.out.println("unsafe put non volatile: " + (System.currentTimeMillis() - beg));
        beg = System.currentTimeMillis();
        for (int i = 0; i < 100000000; i++) {
            test.state = i;
        }
        System.out.println("pojo put non volatile: " + (System.currentTimeMillis() - beg));

        beg = System.currentTimeMillis();
        for (int i = 0; i < 100000000; i++) {
            unsafe.putLong(test, stateOffset,i);
        }
        System.out.println("unsafe put volatile: " + (System.currentTimeMillis() - beg));
        beg = System.currentTimeMillis();
        for (int i = 0; i < 100000000; i++) {
            test.volState = i;
        }
        System.out.println("pojo put volatile: " + (System.currentTimeMillis() - beg));
    }
}

unsafe put non volatile: 179  // 普通属性，直接操作更快。如果使用setter的话，则有时候unsafe快，有时候pojo快。
pojo put non volatile: 68  
unsafe put volatile: 114   // volatile属性，unsafe要快近6倍。
pojo put volatile: 795