Java学习-常用API-ArrayList

  • ArrayList的遍历并删除元素(案例)
  • ArrayList的常用api
  • ArrayList是一种泛型集合
  • ArrayList是什么?有何特点?作用?

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importjava.util.ArrayList;

importjava.util.List;

publicclassapiArrayListDemo1{

publicstaticvoidmain(String[]args){

//常用api的使用

//1.创建一个空的集合对象

ArrayListList=newArrayList<>();List.add("黑马");List.add(5);

System.out.println(List);

//2.将指定元素添加到集合末尾

List.add("程序员");

System.out.println(List);

//3.在集合中指定位置插入指定的元素

List.add(1,"HHH");

System.out.println(List);

//4.返回指定索引处的元素

System.out.println(List.get(2));

//5.返回集合中元素的个数

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

//6.删除指定索引处的元素,返回删除元素

System.out.println(List.remove(2));

System.out.println(List);

//7.删除指定索引处的元素,返回是否删除成功

System.out.println(List.remove("HHH"));

System.out.println(List);

//8.修改指定索引处的元素,返回被修改元素

System.out.println(List.set(1,"黑马"));

System.out.println(List);

}

}

Java学习-常用API-ArrayList_第5张图片

packageapi;

importjava.awt.*;

importjava.util.ArrayList;

publicclassapiArrayListDemo2{

publicstaticvoidmain(String[]args){

//遍历并删除元素:去除低于80的数

//为集合初始化

ArrayListnumList=newArrayList<>();//这里不能使用基本数据类型,所以用Integer

numList.add(88);

numList.add(73);

numList.add(98);

numList.add(66);

numList.add(89);

numList.add(99);

numList.add(88);

numList.add(94);

System.out.println(numList);

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

for(inti=0;i

if(numList.get(i)<=80){

Integerrm=numList.get(i);

numList.remove(rm);i--;

}

}

System.out.println(numList);

}

}

案例:1

Java学习-常用API-ArrayList_第6张图片

packageapi;

importjava.util.ArrayList;

publicclassapiArrayListDemo3{

publicstaticvoidmain(String[]args){

ArrayListshopList=newArrayList<>();

shopList.add("Java入门");

shopList.add("宁夏枸杞");

shopList.add("黑枸杞");

shopList.add("人字拖");

shopList.add("枸杞子");

/*for(inti=0;i

if(shopList.get(i).contains("枸杞")){

shopList.remove(shopList.get(i));i--;//此处如果不加i--,会出现bug

}

}*/

//方法二:倒着遍历数组

for(inti=shopList.size()-1;i>=0;i--){

if(shopList.get(i).contains("枸杞")){

shopList.remove(shopList.get(i));

}

}

System.out.println(shopList);

}

}

案例2:

Java学习-常用API-ArrayList_第7张图片

 

packageapi;

publicclassfood{

privateStringname;

privateStringdesc;

privatedoubleprice;

publicfood(){

}

publicfood(Stringname,Stringdesc,doubleprice){

this.name=name;

this.desc=desc;

this.price=price;

}

publicStringgetName(){

returnname;

}

publicvoidsetName(Stringname){

this.name=name;

}

publicStringgetDesc(){

returndesc;

}

publicvoidsetDesc(Stringdesc){

this.desc=desc;

}

publicdoublegetPrice(){

returnprice;

}

publicvoidsetPrice(doubleprice){

if(price>0)

this.price=price;

}

}

packageapi;

importjava.util.ArrayList;

importjava.util.Scanner;

publicclassfoodOperate{

privateArrayListfoodList=newArrayList<>();

//上架功能

publicvoidaddFood(){

Scannersc=newScanner(System.in);

foodf=newfood();

System.out.println("请输入菜名:");

f.setName(sc.next());

System.out.println("请输入价格:");

f.setPrice(sc.nextDouble());

System.out.println("请输入描述:");

f.setDesc(sc.next());

foodList.add(f);

System.out.println("上架完成~~");

}

//浏览功能

publicvoidlookFood(){

if(foodList.size()==0){

System.out.println("您还没有上架菜品哦,快去上架~~");

}

for(inti=0;i<foodList.size();i++){

System.out.println("菜名:"+foodList.get(i).getName());

System.out.println("价格:"+foodList.get(i).getPrice());

System.out.println("描述:"+foodList.get(i).getDesc());

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

}

}

//设计功能选择页

publicvoidstart(){

Scannersc=newScanner(System.in);

System.out.println("欢迎光临!");

while(true){

System.out.println("请输入您希望办理的业务编号:");

System.out.println("1.上架菜品");

System.out.println("2.浏览菜单信息");

System.out.println("3.退出");

Stringcommand=sc.next();

switch((command)){

case"1":

addFood();

break;

case"2":

lookFood();

break;

case"3":

System.out.println("欢迎下次光临!!");

return;

default:

System.out.println("您输入的信息有误,请检查后重新输入!");

}

}

}

}

importapi.foodOperate;

publicclassapiArrayListDemo4{

publicstaticvoidmain(String[]args){

//结合面向对象编程完成案例

foodOperateFood=newfoodOperate();

Food.start();;

}

}

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