Java 基础(集合三)

ListTest.java

package com.klvchen.java;

import org.junit.Test;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;

public class ListTest {

    @Test
    public void test3(){
        ArrayList list = new ArrayList();
        list.add(123);
        list.add(456);
        list.add("AA");

        //方式一: Iterator迭代器方式
        Iterator iterator = list.iterator();
        while (iterator.hasNext()){
            System.out.println(iterator.next());
        }

        System.out.println("********************");

        //方式二:
        for(Object obj: list){
            System.out.println(obj);
        }

        System.out.println("********************");

        //方式三
        for (int i = 0; i < list.size(); i++){
            System.out.println(list.get(i));
        }
    }

    @Test
    public void test2(){
        ArrayList list = new ArrayList();
        list.add(123);
        list.add(456);
        list.add("AA");
        list.add(new Person("Tom", 12));
        list.add(456);

        //int indexOf(Object obj):返回obj在集合中首次出现的位置。如果不存在，返回-1
        int index = list.indexOf(456);
        System.out.println(index);

        //int lasterIndexOf(Object obj):返回obj在当前集合中末次出现的位置
        System.out.println(list.lastIndexOf(456));

        //Object remove(int index):移除指定位置的元素，并返回此元素
        Object obj = list.remove(0);
        System.out.println(obj);
        System.out.println(list);

        //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);

        //List subList(int fromIndex, int toIndex):返回从fromIndex到toIndex位置的左闭右开集合
        List subList = list.subList(2, 4);
        System.out.println(subList);
        System.out.println(list);
    }

    @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);

        //void add(int index, Object ele): 在index位置插入ele元素
        list.add(1, "BB");
        System.out.println(list);

        //boolean addAll(int index, Collection eles): 从index位置开始将eles中的所有元素
        List list1 = Arrays.asList(1, 2, 3);
        //list.add(list1);
        list.addAll(list1);

        System.out.println(list.size());

        //Object get(int index): 获取指定index位置的元素
        System.out.println(list.get(0));

    }
}

ListExer.java

package com.klvchen.exer;

import org.junit.Test;

import java.util.ArrayList;
import java.util.List;

public class ListExer {

    @Test
    public void testListRemove(){
        List list = new ArrayList();
        list.add(1);
        list.add(2);
        list.add(3);
        updateList(list);
        System.out.println(list);

    }

    private void updateList(List list){
        //list.remove(2);
        list.remove(new Integer(2));
    }
}