Java入门

[toc]

Helloworld

public class Helloworld {
    public static void main(String[] args) {
        System.out.println("你好世界！！！");
    }
}

Scanner

import java.util.Scanner;

public class ScannerDemo {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入第一个数字");
        int number01 = sc.nextInt();
        System.out.println("请输入第二个数字");
        int number02 = sc.nextInt();
        System.out.println(number01 + number02);
    }
}

键盘录入三位数，取其个十百三位

import java.util.Scanner;

public class TextDemo1 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入一个三位数");
        int number01 = sc.nextInt();
        int ge = number01 % 10;
        int shi = number01 / 10 % 10;
        int bai = number01 / 100 % 10;
        System.out.println(ge);
        System.out.println(shi);
        System.out.println(bai);

    }
}

三个和尚

public class Tests {
    public static void main(String[] args) {
        int height1 = 150;
        int height2 = 210;
        int height3 = 165;

        int temp = height1 > height2 ? height1 : height2;
        int max = temp > height3 ? temp : height3;
        System.out.println(max);
    }
}

求回文数

public class Demo01 {
    public static void main(String[] args) {
        int x = 121;
        int temp = x;  //备份x
        int num = 0;  
        while (x != 0){        //从右往左取每一位数字
            int ge = x % 10;   
            x = x / 10;        //修改x记录值
            num = num * 10 + ge;//拼接
        }
        System.out.println(num == temp);

    }

}

求商和余数

public class Demo01 {
    public static void main(String[] args) {
        //定义被除数
        int dividend = 10;
        //定义除数
        int divisor = 3;
        //定义一个变量用来统计相减了多少次
        int count = 0;
        //循环while,在循环中不断用 被除数 - 被数，只要 被除数 > 除数,则一直循环，减剩下的则是余数
        while (dividend >= divisor){
            dividend = dividend - divisor;
            count ++;
        }
        System.out.println("余数为:" + dividend);
        System.out.println("商为:" + count);

    }

}

逢七过

public class Demo01 {
    public static void main(String[] args) {
        for(int i = 1;i <= 100;i ++){
            if(i % 10 == 7 || i / 10 % 10 == 7 || i % 7 == 0){
                System.out.println("过");
                continue;
            }
            System.out.println(i);
        }
    }
}

求平方根

import java.util.Scanner;

public class Demo01 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("请输入一个整数:");
        int number = sc.nextInt();
        for (int i = 1;i <= number;i ++){
            if(i * i == number){
                System.out.println(i + "就是" + number + "的平方根");
                break;
            }else if(i * i > number){
                System.out.println((i - 1) + "就是" + number + "平方根的整数部分");
                break;
            }

        }

    }

}

Random

import org.w3c.dom.ranges.Range;
import java.util.Random;

public class Demo01 {
    public static void main(String[] args) {
        Random r = new Random();
        int number = r.nextInt(100) + 1; // 1~100
        System.out.println(number);
    }
}

猜数字

import org.w3c.dom.ranges.Range;
import java.util.Random;
import java.util.Scanner;

public class Demo01 {
    public static void main(String[] args) {
        Random r = new Random();
        int number = r.nextInt(100) + 1; // 1~100
        Scanner sc = new Scanner(System.in);
        while (true){
            System.out.print("输入你想要输入的数字:");
            int guessNumber = sc.nextInt();
            if (guessNumber > number){
                System.out.println("大了");
            }else if(guessNumber < number){
                System.out.println("小了");
            }else{
                System.out.println("猜中了");
                break;
            }
        }
    }
}