231221 JAVA List01

package coll;

 

import java.util.ArrayList;

import java.util.Arrays;

import java.util.List;

 

public class List01 {

public static void main(String[] args) {

// 부모 //자식

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

 

list.add("홍길동");

list.add("김길동");

list.add("이길동");

list.add("박길동");

list.add("홍길동");

 

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

System.out.println(list.get(0));// 첫번째

System.out.println(list.get(4));// 마지막

System.out.println(list.get(list.size() - 1));// 마지막 size 전체 길이-1

 

System.out.println("==for문===================================");

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

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

}

 

System.out.println("==foteach문===================================");

for (String string : list) {

System.out.println(string);

}

 

System.out.println("==add===================================");

// [홍길동, 황길동, 김길동, 이길동, 박길동, 홍길동]

 

list.add(1, "황길동");// 김길동 자리에 황길동이 들어감

System.out.println(list);

 

// 새로운 컬렉션

List<String> list2 = new ArrayList<String>();

list2.add("데이비드");

list2.add("워쇼스키");

list2.add("바이드");

 

System.out.println("==addAll===================================");

// 두개의 list를 하나로 합치기

list.addAll(list2);

System.out.println(list);

 

System.out.println("==참거짓===================================");

boolean in = list.contains("당근쿤");// 참거짓

boolean in2 = list.contains("황길동");// 참거짓

System.out.println(in);// false

System.out.println(in2);// false

 

System.out.println("==lastIndexOf===================================");

System.out.println(list.lastIndexOf("데이비드"));

System.out.println(list.lastIndexOf("홍길동"));

System.out.println(list.indexOf("홍길동"));

 

System.out.println("==list.toArray===================================");

Object listToArr[] = list.toArray();

 

System.out.println(Arrays.toString(listToArr));

 

System.out.println("===3,5 자리==================================");

List<String> subList = list.subList(3, 5);

System.out.println(subList);// [이길동, 박길동]

 

}

 

}

 

5

홍길동

홍길동

홍길동

==for문===================================

홍길동

김길동

이길동

박길동

홍길동

==foteach문===================================

홍길동

김길동

이길동

박길동

홍길동

==add===================================

[홍길동, 황길동, 김길동, 이길동, 박길동, 홍길동]

==addAll===================================

[홍길동, 황길동, 김길동, 이길동, 박길동, 홍길동, 데이비드, 워쇼스키, 바이드]

==참거짓===================================

false

true

==lastIndexOf===================================

6

5

0

==list.toArray===================================

[홍길동, 황길동, 김길동, 이길동, 박길동, 홍길동, 데이비드, 워쇼스키, 바이드]

===3,5 자리==================================

[이길동, 박길동]