Java -动态数组

1

public class ArrayList {

    //元素的数量
    private int size;
    //元素数组
    private int[] elements;
    //默认容量
    private static final int DEFAULT_CAPACITY= 10;
    //元素未找到
    private static final int ELEMENT_NOT_FOUND= -1;
    public ArrayList(int capacity){
        capacity = (capacity < DEFAULT_CAPACITY) ? DEFAULT_CAPACITY:capacity;
        elements=new int[capacity];
    }

    public ArrayList(){
        this(DEFAULT_CAPACITY);
    }

    public void clear(){

    }

    public int size(){
        return size;
    }

    public boolean isEmpty(){
        return size == 0;
    }

    public void add(int element){
        elements[size]=element;
        size++;
        //
        //elements[size++]=element;
    }

    public int get(int index){
        if (index<0 || index>=size){
            throw new IndexOutOfBoundsException("Index:"+index+", Size:"+size);
        }
        return elements[index];
    }

    public int set(int index,int element){
        if (index<0 || index>=size){
            throw new IndexOutOfBoundsException("Index:"+index+", Size:"+size);
        }
        int old = elements[index];
        elements[index]=element;
        return old;
    }

    public int indexOf(int element){
        for (int i=0;i<size;i++){
            if (elements[i] == element)
                return i;
        }
        return ELEMENT_NOT_FOUND;
    }

    public int remove(int index){
        
        return 0;
    }
}

clear方法

    public void clear(){
        size=0;
    }

让数量等于0，而不是销毁数组或者清空元素。