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  1. import java.util.ArrayList;
  2. import java.util.List;
  3.  
  4. import sun.misc.Unsafe;
  5. import java.lang.reflect.Field;
  6.  
  7. class HelloWorld
  8. {
  9.  
  10.   static final Unsafe unsafe = getUnsafe();
  11.   static final boolean is64bit = true; 
  12.  
  13.   private static class OBJ {
  14.     int one;
  15.     String two;
  16.  
  17.     public OBJ() {
  18.       this.one = 1;
  19.       this.two = "two";
  20.     }
  21.   }
  22.  
  23.   public static void do_it(OBJ o) {
  24.   	System.out.println("o.two is: " + o.two); 
  25.   }
  26.  
  27.   public static void main(String[] args)
  28.   {
  29.  
  30.     System.out.println("start");
  31.  
  32.     List<OBJ> list = new ArrayList<>();
  33.     list.add(new OBJ());
  34.     list.add(new OBJ());
  35.     list.add(new OBJ());
  36.  
  37.     OBJ x = list.get(2);
  38.  
  39.     printAddresses("Address x", x);
  40.  
  41.     for (int idx = 0; idx < 1000000; idx++) {
  42.     	list.add(new OBJ());    
  43.     }
  44.  
  45.     OBJ x2 = list.get(2);
  46.     x2.two = "haha";
  47.  
  48.     printAddresses("Address x", x);
  49.  
  50.     do_it(x);
  51.  
  52.   }
  53.  
  54.     public static void printAddresses(String label, Object... objects) {
  55.         System.out.print(label + ": 0x");
  56.         long last = 0;
  57.         int offset = unsafe.arrayBaseOffset(objects.getClass());
  58.         int scale = unsafe.arrayIndexScale(objects.getClass());
  59.         switch (scale) {
  60.             case 4:
  61.                 long factor = is64bit ? 8 : 1;
  62.                 final long i1 = (unsafe.getInt(objects, offset) & 0xFFFFFFFFL) * factor;
  63.                 System.out.print(Long.toHexString(i1));
  64.                 last = i1;
  65.                 for (int i = 1; i < objects.length; i++) {
  66.                     final long i2 = (unsafe.getInt(objects, offset + i * 4) & 0xFFFFFFFFL) * factor;
  67.                     if (i2 > last)
  68.                         System.out.print(", +" + Long.toHexString(i2 - last));
  69.                     else
  70.                         System.out.print(", -" + Long.toHexString( last - i2));
  71.                     last = i2;
  72.                 }
  73.                 break;
  74.             case 8:
  75.                 throw new AssertionError("Not supported");
  76.         }
  77.         System.out.println();
  78.     }
  79.  
  80.     private static Unsafe getUnsafe() {
  81.         try {
  82.             Field theUnsafe = Unsafe.class.getDeclaredField("theUnsafe");
  83.             theUnsafe.setAccessible(true);
  84.             return (Unsafe) theUnsafe.get(null);
  85.         } catch (Exception e) {
  86.             throw new AssertionError(e);
  87.         }
  88.     }
  89. }
  90.  
Success #stdin #stdout 0.45s 320512KB
comments (?)
stdin 
Standard input is empty
stdout 
start
Address x: 0x525554440
Address x: 0x550882b80
o.two is: haha
https://ideone.com/P3j6xF
language:
Java (HotSpot 12)
created:
9 years ago
visibility:
public

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