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

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");

}

}

}

}