java中打印变量地址

import sun.misc.Unsafe;

import java.lang.reflect.Field;
import java.util.Arrays;
import java.util.Collections;
public class OrderOfObjectsAfterGCMain {
    static final Unsafe unsafe = getUnsafe();
    static final boolean is64bit = true; // auto detect if possible.

    public static void main(String... args) {
        Double[] ascending = new Double[16];
        for(int i=0;i<ascending.length;i++)
            ascending[i] = (double) i;

        Double[] descending = new Double[16];
        for(int i=descending.length-1; i>=0; i--)
            descending[i] = (double) i;

        Double[] shuffled=new Double[16];
        for(int i=0;i<shuffled.length;i++)
            shuffled[i] = (double) i;
        Collections.shuffle(Arrays.asList(shuffled));

        System.out.println("Before GC");
        printAddresses("ascending", ascending);
        printAddresses("descending", descending);
        printAddresses("shuffled", shuffled);

        System.gc();
        System.out.println("\nAfter GC");
        printAddresses("ascending", ascending);
        printAddresses("descending", descending);
        printAddresses("shuffled", shuffled);

        System.gc();
        System.out.println("\nAfter GC 2");
        printAddresses("ascending", ascending);
        printAddresses("descending", descending);
        printAddresses("shuffled", shuffled);
    }

    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);
        }
    }
}