九九乘法表

package com.zhang;
/*
打印九九乘法表*/
public class Test8 {public static void main(String[] args) {//i是竖着的  j是横着的for (int i = 1; i <= 9; i++) {for(int j = 1; j <= 9; j++) {if (i <= j) {System.out.println(i + "*" + j + "=" + i * j);}System.out.println();}}}
}

打印三角形

package com.zhang;
/*打印三角形*****************/
public class Test9 {public static void main(String[] args) {//i是行 j是每行打印*的个数for (int i = 1;i <= 4;i++){for (int k = 1;k <= 4-i;k++){System.out.print(" ");}for (int j = 1;j <= 2*i-1;j++){System.out.print("*");}System.out.println();}}
}

改进:控制行数的三角形

任意行数的三角形，其实还能改进，改进键盘输入

package com.zhang;
/*打印三角形*****************/
public class Test9 {public static void main(String[] args) {//i是行 j是每行打印*的个数//n是你最开始的赋值，想打印多少行int n = 9;for (int i = 1;i <= n;i++){for (int k = 1;k <= n-i;k++){System.out.print(" ");}for (int j = 1;j <= 2*i-1;j++){System.out.print("*");}System.out.println();}}}

有空格的三角形

奇数偶数的判断：
奇数：输出*
偶数：输出 空格

package com.zhang;
/*打印三角形*****************/
public class Test9 {public static void main(String[] args) {//i是行 j是每行打印*的个数//n是你最开始的赋值，想打印多少行int n = 9;for (int i = 1;i <= n;i++){for (int k = 1;k <= n-i;k++){System.out.print(" ");}for (int j = 1;j <= 2*i-1;j++){if (j % 2 == 0){System.out.print("*");}else {System.out.print(" ");}}System.out.println();}}}