java - 将元素添加到没有arrayList的数组中

我试图定义一个称为add（）的方法，该方法将对象Fish添加到数组fish []中。不使用arrayList怎么办？我不断收到错误：
线程“主”中的异常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;}
}

最佳答案

这里是动态数组解决方案，它是ArrayList方法的简单实现。

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;
    }
}