java输出一个对象在内存中的地址

package com.reflection;

import java.lang.reflect.Field;
import sun.misc.Unsafe;
public class test01 {
    static final Unsafe unsafe = getUnsafe();
    static final boolean is64bit = true; // auto detect if possible.
    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);
        }
    }
    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();
    }


    public static void main(String[] args) throws ClassNotFoundException {
        User user1=new User();
        User user2=new User();
int a=0;
        printAddresses("Address", a);
        printAddresses("Address", user1);
        printAddresses("Address", user2);
    }

}
class User
{
    int id;
    String name;
    String school;

    @Override
    public String toString() {
        return "a{" +
                "id=" + id +
                ", name=" + name +  +
                ", school=" + school +  +
                };
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSchool() {
        return school;
    }

    public User() {
    }

    public void setSchool(String school) {
        this.school = school;
    }

    public User(int id, String name, String school) {
        this.id = id;
        this.name = name;
        this.school = school;
    }
}