List in thread..

Question

hi All,
i'm new with thread. so i just starting with the simple program like:
class thread1 implements Runnable{
     private String name;
     public thread1(String nameThread){
          name = new String(nameThread);
     public void run(){
          System.out.println(name+" was sleeping");
           System.out.println(name+" wake up");
class thread{
     public static void main(String[] args){
          Thread student = new Thread(new thread1("student"));
          Thread kid = new Thread(new thread1("kid"));
          Thread sherlock  = new Thread(new thread1("sherlock"));
          student.start();
          kid.start();
          sherlock.start();
}and output:
student was sleeping
kid was sleeping
sherlock was sleeping
student wake up
kid wake up
sherlock wake up
after that, i'm trying to modify this code that create thread automatically depend on element in list but the i still want output was same. so, this my code.
class thread1 implements Runnable{
     private String name[] = {"Student", "kid", "sherlock"} ;
     java.util.List threads = new java.util.ArrayList(Arrays.asList(name));
     public thread1(String name[]){
          this.name = name;
     public void run(){
          for(int i=0; i<2; i++){
          System.out.println(name[i]+" was sleeping");
           System.out.println(name[i]+" wake up");
class thread{
     public static void main(String[] args){
          int T=100;
          String name[] = new String[T];
          Runnable r = new thread1(name);
          Thread t = new Thread(r);
          t.start();
}but the output is:
null was sleeping
null wake up
null was sleeping
null wake up
so, what the problem with my code. hope can anybody give any solution.
thanks.

Answer 1

problem is in your second program you have a private string array names name and that is initialized to a array or nont null strings. But the constructor accepts a string array argument and replace the name with the value of that argument. As a result initialising the name array with the declaration is pointless.
And when you creating a thread1 instance you pass a 'new String[T]' to the constructor which will be assigned to the name array in the thread1 class. But that argument is an uninitialized array which has 100 null elements.