Java

$Class 1$ :

public class Main {
    public static void main(String[] args) {
        System.out.printf("Hello and welcome!\n");
        double x=0.3d; //后缀要加d或者f或者l
        boolean y=false; //不能与数据一起运算
        System.out.println(x);
        System.out.println(y);
        //各种数据类型不支持转换,但是长字节的可以转换到短字节
        short myshort=7;
        byte mybyte=(byte)myshort; //可以进行强制转换
        System.out.println(mybyte);
        byte _x=9;
        short _y=10;
        //_x=_y; //由于y的字节比x长,可能会损失,所以不行
        //_y=_x; //这个就可以,因为y的字节可以完全覆盖掉x
        System.out.println(_y);
    }
}

$Class 2$ :

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

public class Main {
    public static void main(String[] args) {
        int x, y, z;
        x = 1;
        y = 2;
        z = 3;
        //逻辑与,逻辑或,逻辑非等等都与c语言中的类似
        //&&,||表示 并且 和 或者\
        //在逻辑关系中,如果是操作符在判断条件中,会进行逻辑操作,如果是两个整型变量,会进行位操作
        if (x >= 2) System.out.println(1);
        else System.out.println(2);
        boolean f = false;
        System.out.println(!f); //非
        System.out.println(x ^ y); //异或
        System.out.println(x | y); //或
        int now = 8;
        System.out.println(now >> 1); //与c语言类似
        System.out.println(now << 1);

        // 判断 ? 变量 : 变量
        int abc = 1, a = 2, b = 3;
        System.out.println(7 > 5 ? abc : a + b);

        String name = "Alice";
        int age = 30;
        System.out.println("Name: " + name + ", Age: " + age); // 打印多个值，并在最后换行
        System.out.println("Tab\tSeparated\tText"); // 打印带有制表符的文本
        System.out.println("Formatted Number: " + String.format("%.2f", 3.14159)); // 打印格式化的数字

        Scanner scanner = new Scanner(System.in);

        String s = scanner.next();
        String ss = scanner.next();
        System.out.println(s + ss);

        System.out.print("请输入一个整数: ");
        int num = scanner.nextInt();

        System.out.print("请输入一个字符串: ");
        String str = scanner.next();

        System.out.println("你输入的整数是: " + num);
        System.out.println("你输入的字符串是: " + str);

        // 记得关闭Scanner
        scanner.close();
    }
}

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int x, y;
        x = scanner.nextInt();
        y = scanner.nextInt();
        if (x > y) {
            System.out.println(x);
        }
        else {
            System.out.println(y);
        }
        int grade=x/10;
        // switch ,case 语句中在case判断中一定要加break
        switch (grade){
            case 10:
            case 9:
                System.out.println("优秀");
                break;
            case 8:
                System.out.println("lainghao");
                break;
            case 7:
                System.out.println("zhongdeng");
                break;
            case 6:
                System.out.println("jige");
                break;
            default:
                System.out.println("NO");
                break;
        }
        
    }
}