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  1. import sun.misc.Unsafe;
  2. import java.lang.reflect.Field;
  3.  
  4. public class Main {
  5.  
  6.     public static void main(String[] args) throws NoSuchFieldException, IllegalAccessException, InstantiationException {
  7.         /* too lazy to run with VM args, use Reflection */
  8. 	    Field f = Unsafe.class.getDeclaredField("theUnsafe");
  9. 	    f.setAccessible(true);
  10. 	    /* get array address */
  11. 	    Unsafe unsafe = (Unsafe)f.get(null);
  12. 		byte four_bytes[] = {25, 25, 25, 25};
  13. 	    Object trash[] = new Object[] { four_bytes };
  14. 	    long base_offset_bytes = unsafe.arrayBaseOffset(Object[].class);
  15. 	    long four_bytes_address = unsafe.getLong(trash, base_offset_bytes); // <- this is it
  16. 	    long ints_addr = unsafe.allocateMemory(16); // allocate 4 * 4 bytes, i.e. 4 ints
  17. 	    unsafe.copyMemory(four_bytes_address + base_offset_bytes, ints_addr, 4); // copy all four bytes
  18. 	    for(int i = 0; i < 4; i++) {
  19. 		    System.out.println(unsafe.getInt(ints_addr + i)); //run through entire allocated int[],
  20. 		                                                      // get some intestines
  21. 	    }
  22.         System.out.println("************************************");
  23.         for(int i = 0; i < 16; i++) {
  24.     	    System.out.println(unsafe.getByte(ints_addr + i)); //run through entire allocated int[],
  25. 		                                                      // get some intestines
  26. 	    }
  27.     }
  28. }
Success #stdin #stdout 0.06s 380224KB
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stdin
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Standard input is empty
stdout
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421075225
1644825
6425
25
************************************
25
25
25
25
0
0
0
0
0
0
0
0
115
0
0
0
https://ideone.com/e14Omr
language:
Java (12.0.1)
created:
10 years ago
visibility:
public

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