Java简单题

几个比较基础的题目,夯实基础!

求n！+(n-1)!+(n-2)!+………+1！(多组输入)

 public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNext()) {
            int n = scanner.nextInt();
            int i = 1;
            int ret = 1;
            int sum=0;
            while (i<=n) {
                ret *= i;
                sum += ret;
                i++;
            }
            System.out.println(sum);
        }
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do{ 循环语句; }while(循环条件); 先执行循环语句, 再判定循环条件.

猜数字游戏

import java.util.Random;
import java.util.Scanner;

public class GuessNumbers {
    public static void main(String[] args) {
        Scanner scan=new Scanner(System.in);

        Random random = new Random();
        int randNum = random.nextInt(100);[0-99]
        while (true) {
            System.out.println("请输入数字：");
            int num = scan.nextInt();
            if (num < randNum)
                System.out.println("猜小了");
            else if (num > randNum) {
                System.out.println("猜大了");
            } else {
                System.out.println("恭喜你，猜对了");
                break;
            }
        }
    }
}


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根据年龄, 来打印出当前年龄的人是少年(低于18), 青年(19-28), 中年(29-55), 老年(56以上)

import java.util.Scanner;

public class JudgeAge {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNext()) {
            int n=scanner.nextInt();
            if (n <= 18) {
                System.out.println("少年");
            } else if (n < 28) {
                System.out.println("青年");
            } else if (n <= 55) {
                System.out.println("中年");
            } else {
                System.out.println("老年");
            }
        }

    }
}
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打印 1 - 100 之间所有的素数

public class PrintPrimeNum {
   public static void main(String[] args) {
        int count = 0;
        int j = 0;
        for (int i = 1; i <= 100; i += 2) {
            for (j = 2; j <= Math.sqrt(i); j++) {
                if (i % j == 0) {
                    break; //i就不是素数了
                }
            }
            if (j > Math.sqrt(i)) {
                System.out.print(i+"  ");
                count++;
            }
            //每行打印6个数字
            if (count % 6 == 0) {
                System.out.println();
            }
        }
    }
}

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最大公约数（辗转相除法）

import java.util.Scanner;

public class GCD {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNext()) {
            int a=scanner.nextInt();
            int b=scanner.nextInt();
            while (a % b != 0) {
                int c = a % b;
                a = b;
                b = c;
            }
            System.out.println(b);
        }

    }
}

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输入密码

import java.util.Scanner;

public class Password {
    public static void main(String[] args) {
        int n = 3;
        while (n != 0) {
            Scanner scanner = new Scanner(System.in);
            System.out.println("请输入密码：");
            String str=scanner.nextLine();
            if (str.equals("123456")) {
                System.out.println("密码正确");
                break;
            }
            n--;
            if (n == 0) {
                System.out.println("你已经失去机会");
                break;
            }
            System.out.println("你还有"+n+"次机会");
        }

    }
}

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do while 循环

先执行在判断

 public static void main(String[] args) {
        int i = 0;
        int sum=0;
        do {
            sum += i;
            i++;
        } while (i<=10);
        System.out.println(sum);
    }
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只有先夯实基础,才能更好的学习下去!

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