Test Index

Multi Threading

Question : 27

Total: 44

1. public class Transfers {
2.   public static void main(String[] args) throws Exception {
3.    Record r1 = new Record();
4.    Record r2 = new Record();
5.    doTransfer(r1, r2, 5);
6.    doTransfer(r2, r1, 2);
7.    doTransfer(r1, r2, 1);
8.    /*print the result*/
9.    System.out.println("rl = " + r1.get() +", r2=" + r2.get());
10.   }
11.   private static void doTransfer(
12.   final Record a, final Record b, final int amount) {
13.    Thread t = new Thread() {
14.     public void run() {
15.     new Clerk().transfer(a, b, amount);
16.    }
17.   };
18.   t.start();
19.   }
20. }
21. class Clerk {
22.   public synchronized void transfer(Record a, Record b, int amount){
23.    synchronized (a) {
24.     synchronized (b) {
25.      a.add(-amount);
26.      b.add(amount);
27.     }
28.    }
29.   }
30. }
31. class Record {
32.  int num=10;
33.   public int get() { return num; }
34.   public void add(int n) { num = num + n; }
35.   }

If Transfers.main() is run, which three are true? (Choose three.)

The output may be “r1 = 6, r2 = 14”.
The output may be “r1 = 5, r2 = 15”.
The output may be “r1 = 8, r2 = 12”.
The code may run (and complete) with no output.
The code may deadlock (without completing) with no output.
M IllegalStateException or InterruptedException may be thrown at runtime.

Validate

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