public interface IList {
    //新增元素,默认在数组最后新增
    public void add(int data);
    // 在 pos 位置新增元素
    public void add(int pos, int data);
    // 判定是否包含某个元素
    public boolean contains(int toFind) ;
    // 查找某个元素对应的位置
    public int indexOf(int toFind);
    // 获取 pos 位置的元素
    public int get(int pos);
    // 给 pos 位置的元素设为 value  更新
    public void set(int pos, int value);
    //删除第一次出现的关键字key
    public void remove(int toRemove) ;
    // 获取顺序表长度
    public int size();
    // 清空顺序表
    public void clear() ;
    // 打印顺序表，注意：该方法并不是顺序表中的方法，为了方便看测试结果给出的
    public void display();
  //判断是否已满
    boolean isFull();
  //判断是否为空
    public boolean isEmpty();
}

public class MyList implements IList{
    public int[] elem ;
    public int usedSize;//0
    //顺序表的 默认大小
    public static final int DEFAULT_SIZE = 10;
    public MyList(){
        this.elem = new int[DEFAULT_SIZE];
    }
    public MyList(int capacity){
        this.elem = new int[capacity];
    }
 }

public void display(){
        for (int i = 0; i < usedSize; i++) {
            System.out.print(elem[i]+" ");
        }
        System.out.println();
    }

public boolean isFull(){
        return usedSize == elem.length;
     }

 private void checkCapacity(){
        if(isFull()){
            elem = Arrays.copyOf(elem,elem.length*2);
        }
    }
    public void add(int data){
        checkCapacity();
        elem[this.usedSize] = data;
        this.usedSize++;
    }

public void checkPosOnAdd(int pos) throws PosIllegality{
        if(pos < 0 || pos >usedSize){
            System.out.println("不合法！");
            throw new PosIllegality("获取指定下标的元素异常: "+pos);
        }
    }
    public void add(int pos, int data){
        try{
            checkPosOnAdd(pos);
        }
        catch (PosIllegality e){
            e.printStackTrace();
            return;
        }
        checkCapacity();
        for (int i = usedSize-1; i >= pos; i--) {
            elem[i+1] = elem[i];
        }
        elem[pos] = data;
        usedSize++;
    }

package mylist;
public class PosIllegality extends RuntimeException{
    public PosIllegality(String msg){
        super(msg);
    }
}

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

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

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

public void checkPosOnGetAndSet(int pos) throws PosIllegality {
        if(pos < 0 || pos >= usedSize){
            System.out.println("不合法");
            throw new PosIllegality("获取指定下标的元素异常: "+pos);
        }
    }
    public int get(int pos) throws MyArrayListEmpty{
        checkPosOnGetAndSet(pos);
        if(isEmpty()){
                throw new MyArrayListEmpty("获取指定下标元素时" +
                        "顺序表为空！");
        }
            return elem[pos];
    }

package mylist;
public class MyArrayListEmpty extends RuntimeException{
    public MyArrayListEmpty(String msg){
        super(msg);
    }
}

public void set(int pos, int value){
        checkPosOnGetAndSet(pos);
        elem[pos] = value;
    }

  public void remove(int toRemove){
        int index = indexOf(toRemove);
        if(index == -1){
            System.out.println("没有找到");
            return;
        }
        for (int i = index; i < usedSize - 1; i++) {
            elem[i] =elem[i+1];
        }
        usedSize--;
    }

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

public void clear() {
        usedSize = 0;
    }