JAVA获取对象内存地址

为了观察JVM的GC过程中各个对象所处的位置，需要观察JVM各个对象的内存地址，与年轻代与老年代进行比对，确定对象位置。

package com.memory.tools;

import sun.misc.Unsafe;

import java.lang.reflect.Field;

public class AddressPrint {
    private static Unsafe unsafe;

    static
    {
        try
        {
            Field field = Unsafe.class.getDeclaredField("theUnsafe");
            field.setAccessible(true);
            unsafe = (Unsafe)field.get(null);
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }

    public static String addressOf(Object o)
            throws Exception
    {
        Object[] array = new Object[] {o};

        long baseOffset = unsafe.arrayBaseOffset(Object[].class);
        int addressSize = unsafe.addressSize();
        long objectAddress;
        switch (addressSize)
        {
            case 4:
                objectAddress = unsafe.getInt(array, baseOffset);
                break;
            case 8:
                objectAddress = unsafe.getLong(array, baseOffset);
                break;
            default:
                throw new Error("unsupported address size: " + addressSize);
        }

        return(Long.toHexString(objectAddress));
    }


    public static void printBytes(long objectAddress, int num)
    {
        for (long i = 0; i < num; i++)
        {
            int cur = unsafe.getByte(objectAddress + i);
            System.out.print((char)cur);
        }
        System.out.println();
    }
}