Adding elements to an array without arrayList

Question

I am trying to define a method called add() that adds an object Fish to an array fish[]. How would I got about this without using arrayList? I keep receiving the error: Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1

public class Pond {
private Fish[] fish;
private int numFish ;
private int capacity;

public Pond(int capacity){
    this.capacity = capacity;
}
public int getNumFish(){ return numFish;
}
public boolean isFull(){//Ponds can only have so many fish
    boolean Full = false;
    if (numFish >= capacity){
        Full = true;}
    return Full;
}
public void add(Fish aFish) {// puts a fish in the pond--OR-- replaces a fish that has been temporarily removed 
    if (numFish < capacity){
        fish[numFish++] = aFish;}
}

What error are you getting? It looks like the fish array has not been initialised... — CarllDev
– CarllDev, Commented Jan 31, 2014 at 23:47
the error I receive is: Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1 — theGuy05
– theGuy05, Commented Jan 31, 2014 at 23:53
That error is because the array had not been initialised. Do it in the constructor and you'll be fine — CarllDev
– CarllDev, Commented Jan 31, 2014 at 23:54
@CarlDev an uninitialized array would mean throwing a NullPointerException. — SJuan76
– SJuan76, Commented Jan 31, 2014 at 23:59

Ashot Karakhanyan · Accepted Answer · 2014-02-01 00:10:44Z

1

Here dynamic array solution, which is a simple implementation of ArrayList method.

public void add(Fish aFish) {
    ensureCapacity();
    fish[numFish++] = aFish;
}

private void ensureCapacity() {
    if (numFish == fish.length) {
        int newSize = fish.length * 2;
        Fish[] newFish = new Fish[newSize];

        System.arraycopy(fish, 0, newFish, 0, fish.length);
        fish = newFish;
    }
}

edited Feb 1, 2014 at 0:10

answered Feb 1, 2014 at 0:04

Ashot Karakhanyan

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Comments

Alex - GlassEditor.com · Accepted Answer · 2014-02-01 00:05:42Z

0

In your constructor for pond you can add fish = new Fish[capacity] to set the initial size of the fish array to the capacity of your pond. Remember you can not add values to an array only change the values already there.

answered Feb 1, 2014 at 0:05

Alex - GlassEditor.com

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