Java类集-list

Posted 2020-09-19 blfbuaa

 




Collection 子接口：




 

ArrayList是List 接口和Collection接口的一个子类，用于实例化两种接口

 

package leiji;

import java.util.ArrayList;

import java.util.List;

import java.util.Collection;

public class ArryList {

public static void main(String args[]){

List<String> arrlt=new ArrayList<String>();

Collection<String> acoll=new ArrayList<String>();

arrlt.add("Hello");

arrlt.add(0,"World");

System.out.println(arrlt);

//添加元素

acoll.add("jerry");

acoll.add("weibo");

//添加对象

arrlt.addAll(acoll);

arrlt.addAll(0,acoll);

System.out.println(arrlt);

//移除元素

arrlt.remove(1);

arrlt.remove("weibo");

System.out.println(arrlt);

       

//获取元素

for(int i=0;i<=arrlt.size()-1;i++){

//System.out.println(arrlt.get(i));

}

//String a[] =new String[]{"1","2"};

//将集合变为对象数组

String str[]=arrlt.toArray(new String[]{});  //

for(int i=0;i<=str.length-1;i++){

//System.out.println(str[i]);

}

 

Object obj[]=arrlt.toArray();

for(int i=0;i<=obj.length-1;i++){

System.out.println((String)obj[i]);

}

//推断是否为空

System.out.println(arrlt.isEmpty());

//推断是否包括某一个元素

System.out.println(arrlt.contains("Hello")?"Hello is contains":"Hello is not contains");

//截取子集合

List l=arrlt.subList(1, 4);

for(int i=0;i<l.size();i++){

System.out.println(l.get(i));

}

 

System.out.println(l.indexOf("Hello"));

}

 

}