JAVA仿写ArrayList

功能

1.     Object get(int index);  获取该位置数据
2.     boolean add(Object obj);  添加数据
3.     void set(int index, Object obj); 替换该位置数据
4.     boolean remove(int index);    清除该位置数据
5.     boolean isEmpty();  list是否为空
6.     boolean isFull();  list是否已满
7.     int size();       返回当前list大小
8.     void clear();   清除list中所有数据
9.     void show()；遍历显示list内容
10.     void extend()； list扩容

代码：

//接口

package copyList;

public interface List {

    Object get(int index);

    boolean add(Object obj);

    void set(int index, Object obj);

    boolean remove(int index);

    boolean isEmpty();
    
    boolean isFull();
    
    int size();
    
    void clear();
    
}

//实现
package copyList;

import java.util.Arrays;

public class MyArrayList implements List {

	// 数组默认大小
	private static int Length = 0;
	// 数组下标
	private static int tag = 0;
	// 核心数组
	private static Object[] obj;


	public void show() {
		if (obj==null) {
			System.out.println("当前ArrayList空");
		}else {
			for (Object object : obj) {
				if (object==null) {
					continue;
				}else {
					System.out.print(object + " ");
				}
			}
			System.out.println();
		}
		
	}

	@Override
	public Object get(int index) {
		if (obj[index]==null) {
			System.out.print("当前位置没有数据，返回 ");
		}
		return obj[index];
	}
	
	@Override
	public boolean add(Object object) {
		if (isFull()||isEmpty()) {
			extend();
		}
		obj[tag] = object;
		tag++;
		return false;
	}
	
	private void extend() {
		if (Length==0) {
			obj = new Object[10];
			Length = 10;
		}else if (isFull()) {
			Length = (Length>>1)+Length;
			obj = Arrays.copyOf(obj, Length);
		}
	}

	@Override
	public void set(int index, Object obj) {
		this.obj[index] = obj;
	}

	@Override
	public boolean remove(int index) {
		for (int i = index; i < tag; i++) {
			obj[index] = obj[index+1];
			index++;
		}
		tag--;
		return true;
	}

	@Override
	public boolean isEmpty() {
		return obj==null ? true:false;
	}
	
	@Override
	public boolean isFull() {
		return tag==Length ? true:false;
	}

	@Override
	public int size() {
		return tag;
	}

	@Override
	public void clear() {
		obj = null;
		Length = 0;
		tag = 0;
	}

	

}

示例：

本文地址：https://blog.csdn.net/qq_35697978/article/details/107694171