集合06/List接口方法

迈不过友情╰ 2023-10-04 16:52 110阅读 0赞

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA_size_16_color_FFFFFF_t_70]

> 一、

package com.jh;
    
    import java.util.ArrayList;
    import java.util.Arrays;
    import java.util.List;
    
    import org.junit.Test;
    
    public class ListTest {
        
    
        @Test
        public void test1() {
        
            ArrayList list = new ArrayList();
            list.add(123);
            list.add(456);
            list.add("AA");
            list.add(new Person("Tom", 12));
            list.add(456);
            System.out.println(list);
    
            System.out.println("========");
            //void add(int index,Object ele):在index位置插入eLe元素
            list.add(1,"BB");
            System.out.println(list);
    
            System.out.println("========");
            //boolean addAll(int index,Collection eles):从index位置开始将eLes中的所有元素添加进来
            List list1 = Arrays.asList(1,2,3);
            //list.add(list1);//会变成[1, 2, 3]
            list.addAll(list1);//1, 2, 3
            System.out.println(list.size());//9
            System.out.println(list);
    
            System.out.println("========");
            //Object get(int index):获取指定index位置的与元素
            System.out.println(list.get(0));
            
        }
    }

> 结果：  
> ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA_size_16_color_FFFFFF_t_70 1]

> 二、

package com.jh;
    
    import java.util.ArrayList;
    import java.util.List;
    
    import org.junit.Test;
    
    public class ListTest {
        
    
        @Test
        public void test1() {
        
            ArrayList list = new ArrayList();
            list.add(123);
            list.add(456);
            list.add("AA");
            list.add(new Person("Tom", 12));
            list.add(456);
            System.out.println(list);
    
            System.out.println("========");
            //int indexOf(Object obj):返回obj在集合中首次出现的位置
            int index = list.indexOf("AA");//不存在返回-1
            System.out.println(index);
    
            System.out.println("========");
            //int lastIndexOf(Object obj):返回obj在当前集合中末次出现的位置，不存在返回-1
            System.out.println(list.lastIndexOf(456));
    
            System.out.println("========");
            //Object remove(int index):移除指定index位置的元素，并返回此元素
            Object obj = list.remove(0);
            System.out.println(obj);
            System.out.println(list);
    
            System.out.println("========");
            //Object set(int index,Object ele):设置指定index位置的元素为eLe
            list.set(1,"CC");
            System.out.println(list);
    
            System.out.println("========");
            //List subList(int fromIndex,int toIndex):返回从fromIndex到toIndex位置的子集合
            List subList = list.subList(2, 4);
            System.out.println(subList);
            System.out.println(list);//不影响本身list
        }
    }

> 结果：  
> ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA_size_16_color_FFFFFF_t_70 2]

**总结:常用方法**：

> 增: **add(Object obj)**  
> 删: **remove(int index) / remove(Object obj)**  
> 改: **set(int index, Object ele)**  
> 查: **get(int index)**  
> 插: **add(int index,Object ele)**  
> 长度: **size()**  
> 遍历:
> 
> 1.  **Iterator迭代器方式**
> 2.  **增强for循环**
> 3.  **普通的循环**

> [遍历的回顾][Link 1]

--------------------

> ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA_size_16_color_FFFFFF_t_70 3]  
> 这里删除的是索引2
> 
> --------------------
> 
> ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA_size_16_color_FFFFFF_t_70 4]  
> 这里删除的是元素2

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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/7f5b5224b38b4ac0a29cfd52a06417ca.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/383aaebbe4a04f578f7635b669b064bf.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA==,size_16,color_FFFFFF,t_70
[Link 1]: https://blog.csdn.net/weixin_48063660/article/details/119763160?spm=1001.2014.3001.5501
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA_size_16_color_FFFFFF_t_70 4]: https://img-blog.csdnimg.cn/b1e4eccfc96e4feda8d5dda6d8af37f3.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA==,size_16,color_FFFFFF,t_70