循环进阶经典练习题

​ 案例一：输出1-100中被5整除的数，每行输出6个

package loopprc;

public class loopdemo01 {
//输出1-100中被5整除的数，每行输出6个
public static void main(String[] args) {
    int j=0;
    for (int i = 0; i <=100; i++) {
        if (i%5==0){
            System.out.print(i+"\t");
            j++;
            if (j%6==0){
                System.out.println();
            }
        }
    }
}

}

案例二：实现一个功能：

1. 请录入10个int类型的数字，当你输入的数是666的时候，中断程序
2. 判断其中录入的正数的个数并输出
3. 判断系统的推出状态：是正常的推出还是被迫退出

Scanner sc = new Scanner(System.in);
    int count = 0;
    for (int i = 1; i <= 10; i++) {
        System.out.println("请输入第一个："+i+"数字");
        int num = sc.nextInt();
        if (num==666){
            count = 1;
            break;
        }else {
            count = 2;
        }

    }
    if (count==1){
        System.out.println("被迫退出");
    }else {
        System.out.println("正常退出");
    }

案例三：输出乘法口诀

public static void  chengfa(){
    for ( int j =1; j <=9; j++) {
        for (int i = 1; i <=j; i++) {
            System.out.print(i+" * "+j+" = "+(i*j)+" ");
        }
        System.out.println();
    }
}

第二种方法：

for (int i = 9; i >0; i--){
         for ( int j =1; j <=i; j++){
            System.out.print(i+" * "+j+" = "+(i*j)+" ");
        }
        System.out.println();
    }

案例四：打印各种形状：

直角三角形：

public static void zhijiaosanjiao1(){
        for (int i = 0; i <5; i++) {
            for (int j =0; j <i; j++) {
                System.out.print(" "+"*");
            }
            System.out.println(" ");
        }

    }

    public static void zhijiaosanjiao(){
        for (int i = 0; i <5; i++) {
            for (int j =5; j >i; j--) {
                System.out.print(" "+"*");
            }
            System.out.println(" ");
        }
    }

等腰三角形：

public static void dengyaosanjiao(){

        for (int i = 0; i <5; i++) {
            for (int s =5; s >i; s--) {
                System.out.print(" ");
            }
            for (int j =0; j <=i; j++) {
                System.out.print("*"+" ");
            }
            System.out.println(" ");
        }
    }

等腰倒立三角形

public static void dengyaosanjiao2(){

        for (int i = 5; i >=0; i--) {
            for (int s =5; s >i; s--) {
                System.out.print(" ");
            }
            for (int j =0; j <=i; j++) {
                System.out.print("*"+" ");
            }
            System.out.println(" ");
        }
    }

菱形：

public static void lingxing(){
        for (int i = 0; i <5; i++) {
            for (int s =5; s >i; s--) {
                System.out.print(" ");
            }
            for (int j =0; j <=i; j++) {
                System.out.print("*"+" ");
            }
            System.out.println(" ");
        }
        for (int i = 5; i >=0; i--) {
            for (int s =5; s >i; s--) {
                System.out.print(" ");
            }
            for (int j =0; j <=i; j++) {
                System.out.print("*"+" ");
            }
            System.out.println(" ");
        }

空心菱形：

public static void lingxing(){
    for (int i = 0; i <5; i++) {
        for (int s =5; s >i; s--) {
            System.out.print(" ");
        }
        for (int j =0; j <=i; j++) {
            if (j==0||j==i){
                System.out.print(" "+"*");
            }else {
                System.out.print(" "+" ");
            }

        }
        System.out.println(" ");
    }
    for (int i = 5; i >=0; i--) {
        for (int s =5; s >i; s--) {
            System.out.print(" ");
        }
        for (int j =0; j <=i; j++) {
            if (j==0||j==i){
                System.out.print(" "+"*");
            }else {
                System.out.print(" "+" ");
            }
        }
        System.out.println(" ");
    }

}

输出空心的诀窍就是首尾输出。