Java ArrayList底层方法的实现深度解析

public class MyArrayList implements IList{
    private int[] arr;//存储数据
    private int usedSize;//有效数据个数
    public static final int DEFAULT_CAPACITY = 10;//默认数组容量
    public MyArrayList(){
        this.arr = new int[DEFAULT_CAPACITY];
    }

 public void add(int data) {
        //判断顺序表是否满了
        if (isFull()) {
            //扩容
            grow();
        }
        //存储
        this.arr[this.usedSize] = data;
        this.usedSize++;
    }
    public boolean isFull(){
        return this.usedSize == this.arr.length;
    }
    public void grow(){
        this.arr = Arrays.copyOf(this.arr,2*this.arr.length);
    }

public void add(int pos, int data) {
        //检查是不是满的
        if(isFull()){
            grow();
        }
        checkPos(pos,"add方法执行的时候pos位置不合法");
            //判断是不是放在usedSize位置
            if(pos == usedSize){
                arr[pos] = data;
                usedSize++;
                return;
            }
            //如果放在前面，就要移动数据
            for (int i = usedSize-1; i >= pos; i++) {
                arr[i+1] = arr[i];
            }
            arr[pos] = data;
            usedSize++;
    }
    private void checkPosAdd(int pos,String msg) {
        if (pos < 0 || pos > usedSize) {
            throw new PosIllegalityException(msg);
        }
    }

public boolean contains(int toFind) {
        for (int i = 0; i < this.usedSize; i++) {
            if(arr[i] == toFind){
                return true;
            }
        }
        return false;
    }

public int indexOf(int toFind) {
        for (int i = 0; i < this.usedSize; i++) {
            if(arr[i] == toFind){
                return i;
            }
        }
        return -1;
    }

public int get(int pos) {
        if(isEmpty()){
            throw new EmptyListException("当前顺序表为空");
        }
        checkPos(pos,"get方法的pos位置不合法");
        return arr[pos];
    }
    private void checkPos(int pos,String msg){
        if (pos<0 || pos >= usedSize){
            throw new PosIllegalityException(msg);
        }
    }
    public boolean isEmpty(){
        return usedSize == 0;
    }

public void set(int pos, int value) {
        if(isEmpty()){
            throw new EmptyListException("当前顺序表为空");
        }
        checkPos(pos,"set方法执行的时候pos位置不合法"+pos);
        arr[pos] = value;
    }

public void remove(int toRemove) {
        if(isEmpty()){
            throw new EmptyListException("当前顺序表为空");
        }
        //查找要删除数据的下标
        int index = indexOf(toRemove);
        if(index == -1){
            System.out.println("没有你要删除的数据");
            return;
        }
        for (int i = index; i < usedSize-1; i++) {
            arr[i] = arr[i+1];
        }
        usedSize--;
    }
     //arr[usedSize] = null;如果是引用类型，需要手动置空

public int size() {
        return this.usedSize;
    }

public void clear(){
        for (int i = 0; i < this.usedSize; i++) {
            arr[i] = 0;
        }
        usedSize = 0;
    }