Homework 4 - Explain the interesting elements related to threads

CMSC 405 CMSC 335

Homework 4 1. (10 pts)

For the following program, explain the interesting elements related to threads. Focus on explaining the output of the program.

1 public class TaskThreadDemo { 2 public static void main (String args []) { 3 String [] sa = {"a", "X", "+", "."}; 4 for (String s: sa) { 5 Runnable ps = new PrintChar (s, 200); 6 Thread ts = new Thread (ps, s); 7 ts.start (); 8 } // end for each character 9 } // end main 10 } // end class TaskThreadDemo 11 12 class PrintChar implements Runnable { 13 String ch; 14 int times; 15 16 public PrintChar (String c, int n) { 17 ch = c; 18 times = n; 19 } // end constructor 20 21 public void run () { 22 for (int i = 0; i < times; i++) { 23 System.out.print (ch); 24 } // end for loop 25 } // end method run 26 } // end class PrintChar

2. (10 pts) What is changed if the method called on line 7, start(), is replaced with run()? Explain (of course). Focus on explaining the output of the program.

3. (10 pts) What is changed if the method Thread.yield() is added between lines 23 and 24? Explain. Focus on explaining the output of the program.

4. (10 pts) Modify the above program so that the Thread.sleep method is called after each character has been printed causing it to sleep for 500 milliseconds. Describe how that modification has altered the output and explain why the change had the effect that you described.

5. (10 pts) Modify the above program so that the Thread.sleep method is called after each thread is created in the main method causing it to sleep for 500 milliseconds. Describe how that modification has altered the output and explain why the change had the effect that you described.