练习1

打印如下图形：

讯享网

 public static void main(String[] args) { for (int i = 1; i <= 4; i++) { for (int j = 1; j <= i; j++) { System.out.print("*"); } System.out.println(); } }

练习2

打印如下图形：

讯享网 public static void main(String[] args) { for (int i = 1; i <= 4; i++) { for (int j = 1; j <= 4-i; j++) { System.out.print(" "); } for (int j = 1; j <= i; j++) { System.out.print("*"); } System.out.println(); } }

练习3

打印如下图形：

 public static void main(String[] args) { for (int i = 1; i <= 5; i++) { for (int j = 1; j <= 5 - i; j++) { System.out.print(" "); } for (int j = 1; j <= 2 * i - 1; j++) { System.out.print("*"); } System.out.println(); } }

练习4

打印如下图形：

讯享网 public static void main(String[] args) { for (int i = 1; i <= 5; i++) { for (int j = i; j >= 1; j--) { System.out.print(j); } System.out.println(); } }

练习5

打印如下图形

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

练习6

打印如下图形

讯享网 public static void main(String[] args) { for (int i = 1; i <= 5; i++) { for (int j = 0; j < 5 - i; j++) { System.out.print(" "); } for (int j = 1; j < 2 * i - 1; j += 2) { System.out.print(j); } for (int j = 2 * i - 1; j >= 1; j -= 2) { System.out.print(j); } System.out.println(); } }

练习7

打印如下图形

 public static void main(String[] args) { for (int i = 1; i <= 4; i++) { for (int j = 0; j < 4 - i; j++) { System.out.print(" "); } int k = 1;//被打印的那个数 for (int j = 1; j <= i; j++) { System.out.print(k); k *= 2; } k /= 2;//因为上一个循环里面多乘了一个2 for (int j = 1; j < i; j++) {//或者while(k>1) k /= 2; System.out.print(k); } System.out.println(); } }

练习8

打印如下图形：

讯享网 public static void main(String[] args) { for (int i = 5; i > 0; i--) { for (int j = 0; j < 5 - i; j++) { System.out.print(" "); } for (int j = 0; j < 2 * i - 1; j++) { System.out.print("*"); } System.out.println(); } }

练习9

计算1+2+3+...+100的和

 public static void main(String[] args) { int sum = 0; for (int i = 1; i <= 100; i++) { sum += i; } System.out.println(sum); }

练习10

计算1+3+5+...+99的和

讯享网 public static void main(String[] args) { int sum = 0; for (int i = 1; i < 100; i+=2) { sum += i; } System.out.println(sum); }

练习11

读入一个小于10的整数n，输出它的阶乘n

 public static void main(String[] args) { Scanner scanner = new Scanner(System.in); System.out.println("请输入小于10的数"); int num = scanner.nextInt();//验证是否小于10，略 long factorial = 1; for (int i = 1; i <= num; i++) { factorial *= i; } System.out.println(factorial); }

练习12

求100以内所有能被3整除但不能被5整除的数字的和

讯享网 public static void main(String[] args) { int sum = 0; for (int i = 1; i <= 100; i++) { if (i % 3 == 0 && i % 5 != 0) { sum += i; } } System.out.println(sum); }

练习13

“百钱买百鸡”是我国古代的著名数学题。题目描述：3文钱可以买1只公鸡，2文钱可以买一只母鸡，1文钱可以买3只小鸡。用100文钱买100只鸡，那么各有公鸡、母鸡、小鸡多少只？

public static void main(String[] args) { for (int cock = 0; cock <= 100; cock++) {//公鸡 for (int hen = 0; hen <= 100 - cock; hen++) {//母鸡 for (int chick = 0; chick <= 100 - cock - hen; chick += 3) {//小鸡，3只3只买 if (cock + hen + chick == 100 && 3 * cock + 2 * hen + chick / 3 == 100) {//正好100只鸡,100文钱 System.out.println("公鸡：" + cock); System.out.println("母鸡：" + hen); System.out.println("小鸡：" + chick); System.out.println("====================="); } } } } }

练习14

搬砖问题：36块砖，36人搬，男搬4，女搬3，两个小孩抬1砖，要求一次全搬完，问

男、女和小孩各若干？

讯享网 public static void main(String[] args) { for (int men = 0; men <= 36; men++) {//男 for (int women = 0; women <= 36 - men; women++) {//女 for (int children = 0; children <= 36 - men - women; children += 2) {//小孩，2个2个一组 if (men + women + children == 36 && 4 * men + 3 * women + children / 2 == 36) { System.out.println("男：" + men); System.out.println("女：" + women); System.out.println("小孩：" + children); System.out.println("====================="); } } } } }

练习15

编程找出四位整数abcd中满足(ab+cd)(ab+cd)=abcd的数

 public static void main(String[] args) { for (int abcd = 1000; abcd < 10000; abcd++) { int ab = abcd / 100; int cd = abcd % 100; int sum = ab + cd; if (sum * sum == abcd) { System.out.println(abcd); } } }

练习16

读入一个整数n，输出如下图形

思路：

I.读入的整数n，就是外层循环的循环次数。

II.对于每一行，要做的事情：

1).输出若干个空格；

2).输出若干个星；

3).换行。

提示：输出不换行，用System.out.print()。

讯享网 public static void main(String[] args) { Scanner scanner = new Scanner(System.in); System.out.println("请输入一个正整数"); int num = scanner.nextInt(); for (int i = 1; i <= num; i++) { for (int j = 1; j <= num - i; j++) { System.out.print(" "); } for (int j = 1; j <= 2 * i - 1; j++) { System.out.print("*"); } System.out.println(); } }

练习17

输出99乘法表

 public static void main(String[] args) { for (int i = 1; i <= 9; i++) { for (int j = 1; j <= i; j++) { System.out.print(i + "*" + j + "=" + i * j + "\t"); } System.out.println(); } }

练习18

求水仙花数。提示：所谓水仙花数，是指一个三位数abc，如果满足a³+b³+c³=abc，则abc是水仙花数。

讯享网 public static void main(String[] args) { for (int i = 100; i < 1000; i++) { int units = i % 10;//个位 int tens = i / 10 % 10;//十位 int hundreds = i / 100;//百位 if (units * units * units + tens * tens * tens + hundreds * hundreds * hundreds == i) { System.out.println(i + "是水仙花数"); } } }

练习19

韩信带兵不足百人，3人一行排列多1人；7人一行排列少2人；5人一行正好；请写出代码，以计算韩信带了多少人？

 public static void main(String[] args) { for (int i = 1; i < 100; i++) { //三人一排多一人，7人一排少2人(最后一排是5人)，5人一排正好 if (i % 3 == 1 && i % 7 == 5 && i % 5 == 0) { System.out.println(i); } } }