Java Unsynchronized Threads, How Could This Answer Appear and How to Explain It
Which Two Are Possible Results? (Select Two) Public Class Cruiser { Private Int a = 0; Public Void Foo() { Runnable R = New Littlecruiser(); New Thread(R)...
Which two are possible results? (Select two)
public class Cruiser {
private int a = 0;
public void foo() {
Runnable r = new LittleCruiser();
new Thread(r).start();
new Thread(r).start();
}
public static void main(String arg[]) {
Cruiser c = new Cruiser();
c.foo();
}
public class LittleCruiser implements Runnable {
public void run() {
int current = 0;
for (int i = 0; i < 4; i++) {
current = a;
System.out.print(current + ", ");
a = current + 2;
}
}
}
}
- A) 0, 2, 4, 0, 2, 4, 6, 6,
- B) 0, 2, 4, 6, 8, 10, 12, 14,
- C) 0, 2, 4, 6, 8, 10, 2, 4,
- D) 0, 0, 2, 2, 4, 4, 6, 6, 8, 8, 10, 10, 12, 12, 14, 14,
- E) 0, 2, 4, 6, 8, 10, 12, 14, 0, 2, 4, 6, 8, 10, 12, 14,
The correct answers are A and B, however I don't really understand how this code generated A on lower level.
1 Answer
A) 0, 2, 4, 0, 2, 4, 6, 6,
Thread-1: read a = 0;
Thread-2: read a = 0;
Thread-1: output 0, 2, 4
Thread-2: output 0
Thread-2: write 2 back to a
Thread-2: output 2, 4, 6
Thread-2: write 6 back to a;
Thread-1: read a = 6 and output 6
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