package com.yale.test.java;

import java.lang.reflect.Field;

import org.openjdk.jol.vm.VM;

import sun.misc.Unsafe;

public class JavaDemo {

public static void main(String[] args) {

try {

JavaDemo javaDemoAddr = new JavaDemo();

//GC前

System.out.println("-----------GC前------------");

print(javaDemoAddr);

System.out.println("GC垃圾回收前JavaDemo这个类的Class对象地址:" + VM.current().addressOf(JavaDemo.class));

System.out.println("GC垃圾回收前JavaDemo这个类的Class对象地址:" + Integer.toHexString(new JavaDemo().hashCode()));

System.out.println("GC垃圾回收前JavaDemo这个类的Class对象地址:" + Integer.toHexString(JavaDemo.class.hashCode()));

System.out.println("GC垃圾回收前javaDemoAddr对象的地址:" + VM.current().addressOf(javaDemoAddr));

int[] intArrAdrress = new int[10485760];

System.out.println("GC垃圾回收前数组intArrAdrress对象的地址:" + VM.current().addressOf(intArrAdrress));

System.out.println("注意观察这个大数组intArrAdrress是直接分配在了老年代了？还是直接分配在了新生代了?");

// for (int i=0;i<intArrAdrress.length;i++) {

// intArrAdrress[i] = Integer.MAX_VALUE;

// }

System.out.println("GC垃圾回收开始了");

//Thread.sleep(180000);

System.gc();

System.out.println("GC垃圾回收结束了");

System.out.println("GC垃圾回收之后javaDemoAddr对象的地址:GC垃圾回收之后注意看对象的引用地址发生变化了:" + VM.current().addressOf(javaDemoAddr));

System.out.println("GC垃圾回收之后数组intArrAdrress对象的地址:GC垃圾回收之后注意看对象的引用地址发生变化了:" + VM.current().addressOf(intArrAdrress));

System.out.println("GC垃圾回收之后JavaDemo这个类的Class对象地址:" + VM.current().addressOf(JavaDemo.class));

System.out.println("GC垃圾回收前JavaDemo这个类的Class对象地址:" + Integer.toHexString(new JavaDemo().hashCode()));

System.out.println("GC垃圾回收前JavaDemo这个类的Class对象地址:" + Integer.toHexString(JavaDemo.class.hashCode()));

//GC后

System.out.println("-----------GC后------------");

print(javaDemoAddr);

intArrAdrress[1] = 1024;

javaDemoAddr.equals(new JavaDemo());

Thread.sleep(10000000000000000L);

intArrAdrress[2] = 1024;

} catch (InterruptedException e) {

e.printStackTrace();

}

}

static final Unsafe unsafe = getUnsafe();

static final boolean is64bit = true; // auto detect if possible.

private static void print(JavaDemo a) {

// hashcode

System.out.println("Hashcode : " + a.hashCode());

System.out.println("Hashcode : " + System.identityHashCode(a));

System.out.println("Hashcode (HEX) : " + Integer.toHexString(a.hashCode()));// Integer.toHexString(int)是将一个整型转成一个十六进制数

// toString

System.out.println("toString : " + String.valueOf(a));

//通过sun.misc.Unsafe;

printAddresses("Address", a);

}

//https://blog.csdn.net/zhoufanyang_china/article/details/86750351

//从输出信息来看，printAddresses()方法和jol工具类打印的对象的内存地址是一致的，当然如果去深入研究jol工具类，它底层也是通过sun.misc.Unsafe实现的！

@SuppressWarnings("deprecation")

public static void printAddresses(String label, Object... objects) {

System.out.print(label + ": 0x");

long last = 0;

int offset = unsafe.arrayBaseOffset(objects.getClass());

int scale = unsafe.arrayIndexScale(objects.getClass());

switch (scale) {

case 4:

long factor = is64bit ? 8 : 1;

final long i1 = (unsafe.getInt(objects, offset) & 0xFFFFFFFFL) * factor;

System.out.print(Long.toHexString(i1));

last = i1;

for (int i = 1; i < objects.length; i++) {

final long i2 = (unsafe.getInt(objects, offset + i * 4) & 0xFFFFFFFFL) * factor;

if (i2 > last)

System.out.print(", +" + Long.toHexString(i2 - last));

else

System.out.print(", -" + Long.toHexString(last - i2));

last = i2;

}

break;

case 8:

throw new AssertionError("Not supported");

}

System.out.println();

}

private static Unsafe getUnsafe() {

try {

Field theUnsafe = Unsafe.class.getDeclaredField("theUnsafe");

theUnsafe.setAccessible(true);

return (Unsafe) theUnsafe.get(null);

} catch (Exception e) {

throw new AssertionError(e);

}

}

}