Java每日编程day2

Java每日编程day2

第一题

package com.pcx.day2; /* * 九九乘法表并逆序 */ public class JiuJiu {     public static void main(String[] args) {         for (int i = 1; i < 10; i++) {             for (int j = 1; j <= i; j++) {                 System.out.print(j+"*"+i+"="+i*j+"\t");             }             System.out.println();         }                  System.out.println("==========================================");         for (int i = 9; i >0; i--) {             for (int j = 1; j <= i; j++) {                 System.out.print(j+"*"+i+"="+i*j+"\t");             }             System.out.println();         }     } }

第二题

package com.pcx.day2; /** * 在控制台打印菱形 * @author Administrator * */ public class LingXing {     public static void main(String[] args) {         //前三行         for (int i = 0; i <=3; i++) {             for (int j = 0; j <= 2-i; j++) {                 System.out.print(" ");             }             for (int j = 0; j <= 2*i; j++) {                 System.out.print("*");             }             System.out.println();         }         //后三行         for (int i = 0; i <=3; i++) {             for (int j = 0; j <=i; j++) {                 System.out.print(" ");             }             for (int j = 0; j < 5-2*i; j++) {                 System.out.print("*");             }             System.out.println();         }     } }

package com.pcx.day2;   import java.util.Arrays;   /* * 冒泡排序 */ public class PaiXu {     public static void main(String[] args) {         int []array={2,1,3,4,6,67,9,3,54};         for (int i = 0; i < array.length; i++) {             for (int j = i; j < array.length; j++) {                 if (array[i]>array[j]) {                     int temp=array[i];                     array[i]=array[j];                     array[j]=temp;                 }             }         }         System.out.println(Arrays.toString(array));     } }

package com.pcx.day2; /* * １００内的素数 * 素数的因子只有１和他本身 * 对正整数n，如果用2到之间的所有整数去除，均无法整除，则n为质数 */ public class SuShu {     public static boolean isSu(int x) {         for (int i = 2; i <=Math.sqrt(x); i++) {             if (x%i==0) {                 return false;             }         }         return true;     }          public static void main(String[] args) {         for (int i = 2; i < 100; i++) {             if (isSu(i)) {                 System.out.println(i+"是素数");             }         }     } }