简单实现Arraylist链表底层代码

import java.util.Arrays;

public class MyArraylist {

        public int[] elem;
        public int usedSize;//0
        //默认容量
        private static final int DEFAULT_SIZE = 10;

        public MyArraylist() {
                this.elem = new int[DEFAULT_SIZE];
        }

        /**
         * 打印顺序表:
         * 根据usedSize判断即可
         */
        public void display() {
                for (int i = 0; i < this.usedSize; i++) {
                        System.out.print(this.elem[i] + " ");
                }
                System.out.println();
        }

        // 新增元素,默认在数组最后新增
        public void add(int data) {
                if (isFull()) {
                        System.out.println("原数组已经满了");
                        this.elem =
                                Arrays.copyOf(this.elem, 2 * this.elem.length);
                }
                this.elem[this.usedSize] = data;
                this.usedSize++;
        }

        /**
         * 判断当前的顺序表是不是满的！
         *
         * @return true:满   false代表空
         */
        public boolean isFull() {
                return this.usedSize >= this.elem.length;
        }


        private boolean checkPosInAdd(int pos) {
                if (pos >= this.elem.length || pos < 0) {
                        System.out.println("所输入的pos不合法");
                        return false;
                }
                return true;//合法
        }

        // 在 pos 位置新增元素
        public void add(int pos, int data) throws PosWrongfulException {
                if (isFull()) {
                        System.out.println("原数组已满");
                        this.elem =
                                Arrays.copyOf(this.elem, 2 * this.elem.length);
                }
                if (!checkPosInAdd(pos)) {
                        System.out.println("所输入的pos不合法");
                        throw new PosWrongfulException("pos位置不合法");
                }
                for (int i = this.usedSize - 1; i >= pos; i--) {
                        this.elem[i + 1] = this.elem[i];
                }
                this.elem[pos] = data;
                this.usedSize++;

        }

        // 判定是否包含某个元素
        public boolean contains(int toFind) {
                for (int i = 0; i < this.usedSize; i++) {
                        if (this.elem[i] == this.elem[toFind]) {
                                return true;
                        }
                }
                System.out.println("未包含该元素");
                return false;
        }

        // 查找某个元素对应的位置
        public int indexOf(int toFind) {
                for (int i = 0; i < this.usedSize; i++) {
                        if (this.elem[i] == toFind) {
                                return i;
                        }
                }
                return -1;
        }

                // 获取 pos 位置的元素
                public int get_pos ( int pos){
                if(isEmpty()){
                        System.out.println("数组为空无法获取");
                        throw new EmptyException("当前顺序表为空！");
                }
                if(!checkPosInAdd(pos)){
                        System.out.println("所输入的pos不合法");
                        throw new PosWrongfulException("pos位置不合法");
                }
                return this.elem[pos];
                }

                private boolean isEmpty () {
                        return this.usedSize == 0;
                }
                // 给 pos 位置的元素设为【更新为】 value
                public void set_pos ( int pos, int value){
                        if(isEmpty()){
                                System.out.println("数组为空无法获取");
                                throw new EmptyException("当前顺序表为空！");
                        }

                        if(!checkPosInAdd(pos)){
                                System.out.println("所输入的pos不合法");
                                throw new PosWrongfulException("pos位置不合法");
                        }

                        this.elem[pos]=value;

                }

                /**
                 * 删除第一次出现的关键字key
                 * @param key
                 */
                public void remove ( int key){
                        if(isEmpty()){
                                System.out.println("数组为空无法获取");
                                throw new EmptyException("当前顺序表为空！");
                        }
                        if(!checkPosInAdd(key)){
                                System.out.println("所输入的key不合法");
                                throw new PosWrongfulException("key位置不合法");
                        }
                        int index=indexOf(key);
                        if(index==-1){
                                System.out.println("不存在此数字");
                        }
                        for(int i=index;i<this.usedSize;i++){
                                this.elem[i]=this.elem[i+1];
                        }
                }

                // 获取顺序表长度
                public int size () {
                        return this.usedSize;
                }

                // 清空顺序表
                public void clear () {
            for(int i=0;i<this.usedSize;i++){
                    this.elem[i]=0;
                    this.usedSize--;
            }
                }

        }
----------------------分割线-------------------------------
public class PosWrongfulException extends RuntimeException{
    public PosWrongfulException() {

    }
    public PosWrongfulException(String message) {
        super(message);
    }
}
---------------------分割线---------------------------------
public class EmptyException extends RuntimeException{
    public EmptyException() {
    }

    public EmptyException(String message) {
        super(message);
    }
}