Thread: What is going on here?

Hey all,

So about two weeks ago I decided that I was going to dive in and finally learn a programming language. Of course I am here because I chose Java. Aside from numerous online resources, I also purchased Head First Java, which I think has been really amazing at explaining concepts. I have to admit some of the assignments it give are really difficult for a beginner, but I have been managing up until now. Can someone please tell me what is going on here? The assignment is to determine which of the reference variable refer to which objects. Not all reference variables will be used.

class HeapQuiz {
 
   int id = 0;
 
   public static void main (String [] args) {
      int x = 0
      HeapQuiz [] hq = new HeapQuiz[5];
      while ( x < 3) {
          hq[x] = new HeapQuiz();
          hq[x].id = x;
          x = x = 1;
       }
 
       hq[3] = hq[1];
       hq[4] = hq[1];
       hq[3] = null;
       hq[4] = hq[0];
       hq[0] = hq[3];
       hq[3] = hq[2];
       hq[2] = hq[0];
    }
}

Here are the answers...

hq[1] -----> id = 1
hq[3] -----> id = 2
hq[4] -----> id = 0


I understand that an array is created. I think I understand the hq[x] represents the the array positions, but how is x being assigned? How does the JVM progress through the loop? The answers are posted above, but I have not idea how the loop is producing those answers. Any help is greatly appreciated. Thanks in advance.

The Noobiest of all Noobs

Hey all,

So about two weeks ago I decided that I was going to dive in and finally learn a programming language. Of course I am here because I chose Java. Aside from numerous online resources, I also purchased Head First Java, which I think has been really amazing at explaining concepts. I have to admit some of the assignments it give are really difficult for a beginner, but I have been managing up until now. Can someone please tell me what is going on here? The assignment is to determine which of the reference variable refer to which objects. Not all reference variables will be used.

class HeapQuiz {
 
   int id = 0;
 
public static void main (String [] args) {
      int x = 0; 
     HeapQuiz [] hq = new HeapQuiz[5];
          while ( x < 3) {
          hq[x] = new HeapQuiz();
          hq[x].id = x;
         x = x = 1;
     }
 
        hq[3] = hq[1];
        hq[4] = hq[1];
        hq[3] = null;
        hq[4] = hq[0];
        hq[0] = hq[3];
        hq[3] = hq[2];
        hq[2] = hq[0];
    }
}

Here are the answers...

hq[1] -----> id = 1
hq[3] -----> id = 2
hq[4] -----> id = 0


I understand that an array is created. I think I understand the hq[x] represents the the array positions, but how is x being assigned? How does the JVM progress through the loop? The answers are posted above, but I have not idea how the loop is producing those answers. Any help is greatly appreciated. Thanks in advance.

The Noobiest of all Noobs

Have you tried to compile the posted code? Were there any errors?

I don't see where x is declared. That should cause a compiler error.

Please edit your post and wrap your code with code tags:

[code]
**YOUR CODE GOES HERE**
[/code]

to get highlighting and preserve formatting.

What happens when you compile and execute the posted code?
How do you know what is in any of the variables? There aren't any print statements to show the contents of the variables.