Java program runtime error

Question

public class Hobbits {
 String name;

 public static void main(String[] args){

  Hobbits [] h = new Hobbits[3];
  int z = 0;

  while (z<4) {
   z = z + 1;
   h[z] = new Hobbits();
   h[z].name = "Bilbo";
   if (z == 1) {
    h[z].name = "Frodo";
   }
   if (z == 2){
    h[z].name = "Sam";
   }
   System.out.print(h[z].name+ " is a ");
   System.out.println("good Hobbit name");

  }
 }
}

At runtime this program is giving the exception:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException

Some exception, you say? Well, then something is wrong. :) (hint: be more specific) — Bart Kiers
– Bart Kiers, Commented Jan 15, 2011 at 15:53
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 3 Frodo is a good Hobbit name Sam is a good Hobbit name at Hobbits.main(Hobbits.java:12) — Sam
– Sam, Commented Jan 15, 2011 at 15:54
You can use a for loop and it will do the index incrementing in a cleaner manner. Also, use z < h.length as the loop condition and you will never overrun an array. — unholysampler
– unholysampler, Commented Jan 15, 2011 at 16:00

biziclop · Accepted Answer · 2011-01-15 15:56:08Z

3

Agree with the comment, you should've been more specific, however by looking at the code I can see that your loop runs from 1 to 3 and your array has a length of only 3 (so the highest available index is 2).

answered Jan 15, 2011 at 15:56

biziclop

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Comments

Nanne · Accepted Answer · 2011-01-15 15:56:11Z

2

H has h[0], h[1] and h[2]. You're asking for h[3] there :)

answered Jan 15, 2011 at 15:56

Nanne

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Comments

jzd · Accepted Answer · 2011-01-15 15:58:10Z

2

Your array is 3 long.

1: Array indices start at 0.

2: Your code goes up to index 4 when 2 is the highest in your array:

 while (z<4) {
       z = z + 1;
       h[z] = new Hobbits();
       ...
 }

answered Jan 15, 2011 at 15:58

jzd

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Comments

Noray · Accepted Answer · 2011-01-15 15:55:33Z

1

I guess you are getting IndexOutOfBoundsException - and it, because you are incrementing z before creating h[z] instance. just increment in the end of the loop.

answered Jan 15, 2011 at 15:55

Noray

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2 Comments

Sam Over a year ago

If I increment z in the end of the loop, still I am getting exception belowBilbo is a good Hobbit name Frodo is a good Hobbit name Sam is a good Hobbit name Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 3 at Hobbits.main(Hobbits.java:11)

dm76 Over a year ago

Noray is right, your array has a length of 3 meaning it cna have index 0, 1 and 2. So the condition must be that z doesn't reach 3

fmucar · Accepted Answer · 2011-01-15 16:03:24Z

1

you need to move z = z + 1; to the end of the while loop

answered Jan 15, 2011 at 16:03

fmucar

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2 Comments

jzd Over a year ago

This will not solve the problem because the code will still go to index 3 with is still out of bounds.

fmucar Over a year ago

Correct, sysout at the end will throw an exception. that should also be converted to [z-1]

Peter Lawrey · Accepted Answer · 2011-01-15 16:13:30Z

1

For your interest, a shorter version might look like this.

String[] names = "Bilbo,Frodo,Sam".split(",");
Hobbits[] h = new Hobbits[names.length];
for(int i=0;i<names.length;i++) {
   h[i] = new Hobbits();
   h[i].name = names[i];
   System.out.print(h[i].name+ " is a good Hobbit name");
}

The class Hobbits is redundant and you would get the same output with.

for(String name: "Bilbo,Frodo,Sam".split(","))
   System.out.print(name+ " is a good Hobbit name");

answered Jan 15, 2011 at 16:13

Peter Lawrey

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Comments

dm76 · Accepted Answer · 2011-01-15 18:56:45Z

1

move z=z+1 to the end of the loop
change the condition of the while loop to z<3

answered Jan 15, 2011 at 18:56

dm76

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Comments

Costis Aivalis · Accepted Answer · 2011-01-15 16:00:48Z

0

The exception is because of subscript error, but what is the point of having such a class?
I think that it would be a better approach to have a Hobbit class with one or two constructors some accessors and some mutators. Then it would make sense to add either a main or a TryHobbit class with a main that does its tricks with the array etc. That would provide a "cleaner" learning example.

answered Jan 15, 2011 at 16:00

Costis Aivalis

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Comments

YK-47 · Accepted Answer · 2011-08-18 02:11:26Z

0

Try this and it should work.

int  z  =  -1
while   (z  < 2)

answered Aug 18, 2011 at 2:11

YK-47

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