About List [Java]

Initialization ① add


package com.test;

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

public class Main {
    public static void main(String[] args) {
        List<String> animals = new ArrayList<>();
        System.out.println(animals); // [dog, cat, pig]

Initialization ② Arrays.asList


package com.test;

import java.util.Arrays;
import java.util.List;

public class Main {
    public static void main(String[] args) {
        List<String> animals = Arrays.asList("dog", "cat", "pig");
        System.out.println(animals); // [dog, cat, pig]

Returns the current number of elements size

System.out.println(animals.size()); // 3

Reference element by specifying index get (index)

0 → Refer to the first element See 1 → 2nd element See 2 → 3rd element ...etc

 for (int i = 0; i < animals.size(); i++) {
     System.out.print(animals.get(i) + ","); // dog,cat,pig,

Remove by specifying index remove (index)

0 → Delete 1st Delete 1 → 2 Delete 2nd → 3rd ...etc

System.out.println(animals); // [dog, pig]

Delete all elements clear

System.out.println(animals); // []

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