1. (20 pts) For the following program, explain the interesting elements related to threads. 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