第三次上机练习

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 a;

import java.util.Scanner;

public class sss {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		for (int i = 100; i < 1000; i++) {
			int a = i / 100;
			int b = i / 10 % 10;
			int c = i % 10;
			if (Math.pow(a, 3) + Math.pow(b, 3) + Math.pow(c, 3) == i)
			System.out.println("水仙花数 : " +i);
			}
		}
}

　　

2.在控制台输出以下图形（知识点：循环语句、条件语句）（ 四个位置经过翻转的直角三角形）

package a;

import java.util.Scanner;

public class sss {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		for(int a = 1;a <= 6;a++)
		{
			for(int i = 1;i <= a;i++)
				System.out.printf("%d ",i);
			System.out.print("
");
		}
		System.out.print("
");
		
		for(int a = 6;a >= 1;a--)
		{
			for(int i = 1;i <= a;i++)
				System.out.printf("%d ",i);
			System.out.print("
");
		}
		System.out.print("
");
		
		for(int a = 1;a <= 6;a++)
		{	
			for(int i = 1;i <= 2 * (6 - a);i++)
				System.out.print(" ");
			
			for(int i = a;i >= 1;i--)
				System.out.printf("%d ",i);
			System.out.print("
");
		}
		System.out.print("
");
		
		for(int a = 6;a >= 1;a--)
		{
			for(int i = 1;i <= 2 *(6-a);i++)
				System.out.print(" ");
			for(int i = 1;i <= a;i++)
				System.out.printf("%d ",i);
			System.out.print("
");
		}
	}
}

　　

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 a;

import java.util.Scanner;

public class sss {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		int year, month, day; 
	     int days = 0; 
	     int d = 0; 
	     int e; 
	     input fymd = new input(); 
	     do { 
	     e = 0; 
	     System.out.print("输入年�"); 
	     year =fymd.input(); 
	     System.out.print("输入月�"); 
	     month = fymd.input(); 
	     System.out.print("输入天�"); 
	     day = fymd.input(); 
	     if (year < 0 || month < 0 || month > 12 || day < 0 || day > 31) { 
	     System.out.println("输入错误�请重新输入�"); 
	     e=1 ;    } 
	     }while( e==1); 
	      for (int i=1; i <month; i++) { 
	      switch (i) { 
	      case 1: 
	      case 3: 
	      case 5: 
	      case 7: 
	      case 8: 
	      case 10: 
	      case 12: 
	       days = 31; 
	      break; 
	      case 4: 
	      case 6: 
	      case 9: 
	      case 11: 
	       days = 30; 
	      break; 
	      case 2: 
	       if ((year % 400 == 0) || (year % 4 == 0 && year % 100 != 0)) { 
	        days = 29; 
	       } else { 
	        days = 28; 
	       } 
	       break; 
	      } 
	      d += days; 
	      } 
	     System.out.println(year + "-" + month + "-" + day + "是这年的第" + (d+day) 
	+ "天。"); 
	} 
	} 
	class input{ 
	public int input() { 
	     int value = 0; 
	     Scanner s = new Scanner(System.in); 
	     value = s.nextInt(); 
	     return value; 
	} 
	}  

　　

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 a;

import java.util.Scanner;

public class sss {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc=new Scanner(System.in);
	    System.out.println("请输入一个四位数");
	    int n=sc.nextInt(); 
	    int a = n / 1000; 
	    int b = n / 100 % 10; 
	    int c = n / 10 % 10; 
	    int d = n % 10; 
	    int s = d * 1000 + c * 100 + b * 10 + a; 
	    System.out.println("反转后数为�" + s); 
	}
}