Java基础题目

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!