4.2java作业

1. 打印出所有的"水仙花数"，所谓"水仙花数"是指一个三位数，其各位数字立方和等于该数本身。例如：153是一个"水仙花数"，因为153=1的三次方＋5的三次方＋3的三次方。（知识点：循环语句、条件语句）

package demo01;
public class demo001 {

        public static void main(String[] args) {
             for(int i = 100 ; i <= 999 ; i++){
                 int bai = i/100;
                 int shi = i/10 % 10;
                 int ge = i % 10;
                 if( i==bai*bai*bai+shi*shi*shi+ge*ge*ge)
                 System.out.println(i);
             }
        }    
}

在控制台输出以下图形（知识点：循环语句、条件语句）

package demo01;
public class demo001 {

        public static void main(String[] args) {
             for(int i = 1; i <= 6; i++){
                 for (int j = 1; j <= i; j++) 
                     System.out.print(j);
                 System.out.println("
");
                 }
        }    
}

package demo01;
public class demo001 {

        public static void main(String[] args) {
             for(int i = 1; i <= 6; i++){
                 for (int j = 1; j <= 7-i; j++) 
                     System.out.print(j);
                 System.out.println("
");
                 }
        }    
}

package demo01;
public class demo001 {

        public static void main(String[] args) {
             for(int i = 1; i <= 6; i++){
                 for (int k = 1; k <7-i ; k++) {
                        System.out.print(" ");
                 }
                 for (int j = i; j >0; j--) 
                     System.out.print(j);
                 System.out.println("
");
             }
        }    
}

package demo01;
public class demo001 {

        public static void main(String[] args) {
            for(int i=6;i>0;i--) {
                for(int k=0;k<6-i;k++) {
                    System.out.print(" ");
                }
                for(int j=1;j<=i;j++) {
                    System.out.print(j);
                }
                System.out.println("");
            }
        }    
}

3. 输入年月日，判断这是这一年中的第几天（知识点：循环语句、条件语句）

package demo01;
import java.util.Scanner;
public class demo001 {
        public static void main(String[] args) {
            Scanner input=new Scanner(System.in);
            System.out.println("year");
            int year=input.nextInt();
            System.out.println("month");
            int month=input.nextInt();
            System.out.println("day");
            int day=input.nextInt();
            int total=0;
            for (int i = 1; i < month; i++) {
                switch(i) {
                case 4:
                case 6:
                case 9:
                case11:
                    total+=30;
                break;
                case 2:
                    if(year%4==0&&year%100!=0||year%400==0)
                    total+=29;
                    else
                        total+=28;
                    break;
                    default:
                        total+=31;
                        break;
                    }
            
        }    
            total+=day;
            System.out.println("该天是第"+total+"天");
        }
}

4．由控制台输入一个4位整数，求将该数反转以后的数，如原数为1234，反转后的数位4321（知识点：循环语句、条件语句

package demo01;
import java.util.Scanner;
public class demo001 {
        public static void main(String[] args) {
            Scanner input=new Scanner(System.in);
            System.out.println("输出一个四位数");
            int i=input.nextInt();
            int ge=i%10;
            int shi=i%100/10;
            int bai=i%1000/100;
            int qian=i/1000;
            System.out.print(ge);
            System.out.print(shi);
            System.out.print(bai);
            System.out.print(qian);        
        }
}