まだ意味は全く分からない！一々覚えましょう

import javax.swing.*;
import java.util.ArrayList;
import java.util.Random;
import java.util.Scanner;

public class Main {

public  static void main(String[] args) {
    System.out.println("Hello world!");
    System.out.println("35");
    System.out.println("35 + 30");
    System.out.println("x + 20");
    x = 40;
    System.out.println(X);
    final int y =30;
    y = 20;
    //정수
    int x = 30;
    long l = 30L;
    short s = 30;
    byte b = 30;

    int i = (int) 30L;
    long ll = 30; //int

    dd = ff;
    ff = (float) dd;
    double dd= 30.0;
    float ff = 30.0f;

    boolean isMarried = true;
    char c = 'a';
    char cc = '한';

    String str = "여러 글자";
    System.out.printf("저는 %s입니다. 나이는 %d살이구요, 키는 %fcm입니다.","홍길동"/n;, 20, 180.5f);
    String str2 = String.format("저는 %s입니다. 나이는 %d살이구요, 키는 %fcm입니다.","홍길동", 20, 180.5f);
    System.out.println(str2);
}
}

    public  static void main(String[] args) {
    String str = "100";
    int i= Integer.parseInt(str);
        long l =Long.parseLong(str);
    String str2 = String.valueOf(i);
        System.out.println(i);
        System.out.println(str2);
    )
Random = new Random();
int rand = random.nextInt(bound:4) + 5; // 5 ~ 9
 //0 ~ 4 => 5 ~ 14
 // 5~9
        System.out.println(rand);


            Scanner scanner = new Scanner(System.in);

            String str = scanner.next()
                    int i = scanner.nextInt();
            long l = scanner.nextLong();
            System.out.println(next);

        public  static void main(String[] args) {
            int i = 6;
            if (i>5) {
                System.out.println("참");
            }  else if ( i < 5) {
                System.out.println("거짓");
            }else{
                System.out.println("나머지");
            }
        }
    }
    public  static void main(String[] args) {
    boolean isMarried = true;
        boolean isMam = false;
    String str;
    str = isMarried ? "결혼했다" : "결혼 안 했다";

        if (!isMarried !isMarried) {
    if (isMarried) {
        str = "결혼했다";
    } else {
        str = "결혼 안 했다";
    }
switch (str) {
    case "결혼했다":
        System.out.println("o");
        break;
    case "결혼 안 했다":
        System.out.println("x");
        break;
    default:
        System.out.println("?");
}
        System.out.println(str);
}
        public  static void main(String[] args) {
            for (int i = 0; i <10; i++) {
                System.out.println(i);
                int i = 0;
                while (i < 10) {
                    System.out.println(i);
                    i++;
                }
                int i = 0;
                do {
                    System.out.println(i);
                    i++;
                } while (i < 10);
                public  static void main(String[] args) {
                    for (int i = 0; i <10; i++) {
                        System.out.println(i);  }
                }
                if ( i = 6) {
            }break;
                if ( i = 6) {
continue;
                    public  static void main(String[] args) {
                        int[] score ={ 10, 20, 30, 40, 50};
                        score = new int[5]
                        int count = score.length;
                        System.out.println(count);

                        score[0] = 10;
                        System.out.println(score[score.length - 1]);

                        String[] names = {"홍길동", " 이순신"};
                        String[] names = news String[2];


                        System.out.println(names[0].length());
                }
    }ArrayList<Integer> scoreList = new ArrayList<>();
                scoreList.add(10);
                scoreList.add(20);
                scoreList.add(30);
                scoreList.add(40);
                scoreList.add(50);
                scoreList.add(index:2, element:200);
                scoreList.remove()
                System.out.println(scoreList);

                public  static void main(String[] args) {
                    public static int add(int x, int y){
                        System.out.println(x + y);

                        return x + y;
                        public static int add(int x, int y, int z){
                            return x + y + z;
                 public static int add(int... numbers){
                     int sum = 0;
                     for (int i = 0; i < numbers.length; i++){
                         sum = sum + i;
                     }
                            }
                        }
                }
                import models.Person
                class Person{
                private String name;
                    private int age;
Person(){
}

                }
                    public String getName() {
                        return name;
                    }

                    public void setName(String name, int age) {
                        this.name = name;
                    }this.age = age;

                    public int getAge() {
                        return age;
                    }

                    public void setAge(int age) {
                        this.age = age;
                    }
                }

    @Override
    public String toString() {
        return "Person{" +
   "name='" + name + '/'' +
                    ", age=" + age +
                            '}';
                }