如何在Java中使用嵌套循环打印数学乘法表，以2×2和3×3矩阵形式返回字符串值

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英文:

How to print math multiplication table returning String value in 2x2 and 3x3 matrix using nested loops in Java

问题

  1. public String simpleMultiplicationTable(int num) {
  2.     StringBuilder output = new StringBuilder();
  4.     for (int i = 1; i <= num; i++) {
  5.         for (int j = 1; j <= num; j++) {
  6.             output.append(String.format("%4d", i * j));
  7.         }
  8.         output.append("\n");
  9.     }
  10.     return output.toString();
  11. }

请注意，我已经根据您提供的内容为您进行了翻译。如果您有任何其他需要翻译的内容或问题，请随时提问。

英文:

I'm trying to get the method that would return the following String for an integer parameter of 2:

Output:

如何在Java中使用嵌套循环打印数学乘法表，以2×2和3×3矩阵形式返回字符串值

Same for parameter of 3

如何在Java中使用嵌套循环打印数学乘法表，以2×2和3×3矩阵形式返回字符串值

The code which I got so far is below:

  1. public String simpleMultiplicationTable(int num) {
  2.     for(int i = 1 ;i&lt;=num;i++) {
  3.         for(int j=1;j&lt;=num;j++) {
  4.             System.out.format(&quot;%4d&quot;,i*j);
  5.         }
  6.         System.out.println();
  7.     }
  8.     return String.valueOf(num);      
  9. }

答案1

得分: 0

代码部分已翻译如下：

  1. // 使用 StringBuilder 而不是打印每个值，将其附加到 StringBuilder，并在最后返回。
  3. public class Main {
  4.     public static void main(String[] args) {
  5.         // 测试
  6.         System.out.println(simpleMultiplicationTable(2));
  7.         System.out.println(simpleMultiplicationTable(3));
  8.     }
  10.     public static String simpleMultiplicationTable(int num) {
  11.         StringBuilder sb = new StringBuilder();
  12.         for (int i = 1; i <= num; i++) {
  13.             for (int j = 1; j <= num; j++) {
  14.                 sb.append(i * j);
  15.                 if (j < num) {
  16.                     sb.append(" ");
  17.                 }
  18.             }
  19.             if (i < num) {
  20.                 sb.append("\n");
  21.             }
  22.         }
  23.         return sb.toString();
  24.     }
  25. }
  27. **输出:**
  29. 1 2
  30. 2 4
  31. 1 2 3
  32. 2 4 6
  33. 3 6 9
  35. 使用 `String` 替代 `StringBuilder`：
  36. ====
  38. public class Main {
  39.     public static void main(String[] args) {
  40.         // 测试
  41.         System.out.println(simpleMultiplicationTable(2));
  42.         System.out.println(simpleMultiplicationTable(3));
  43.     }
  45.     public static String simpleMultiplicationTable(int num) {
  46.         String table = "";
  47.         for (int i = 1; i <= num; i++) {
  48.             for (int j = 1; j <= num; j++) {
  49.                 table += j < num ? i * j + " " : i * j;
  50.             }
  51.             if (i < num) {
  52.                 table = table + "\n";
  53.             }
  54.         }
  55.         return table;
  56.     }
  57. }
  59. JUnit 测试
  60. ======== 
  62. import static org.junit.Assert.assertEquals;
  63. import static org.junit.Assert.fail;
  65. import org.junit.jupiter.api.Test;
  67. class TestMethods {
  69.     @Test
  70.     public void testSimpleMultiplicationTable() {
  71.         Table table = new Table();
  72.         String result = table.simpleMultiplicationTable(2);
  73.         if (result.contains(" \n")) {
  74.             fail("你的输出表格在换行字符之前有一个或多个额外的空格。你可以使用 trim() 函数去除额外的空格");
  75.         }
  76.         assertEquals("1 2\n2 4", result);
  78.         result = table.simpleMultiplicationTable(1);
  79.         if (result.contains(" \n")) {
  80.             fail("你的输出表格在换行字符之前有一个或多个额外的空格。你可以使用 trim() 函数去除额外的空格");
  81.         }
  82.         assertEquals("1", result);
  83.     }
  84. }
  86. class Table {
  88.     public String simpleMultiplicationTable(int num) {
  89.         String table = "";
  90.         for (int i = 1; i <= num; i++) {
  91.             for (int j = 1; j <= num; j++) {
  92.                 table += j < num ? i * j + " " : i * j;
  93.             }
  94.             if (i < num) {
  95.                 table = table + "\n";
  96.             }
  97.         }
  98.         return table;
  99.     }
  100. }
英文:

Instead of printing each value, append it to a StringBuilder and return the same at the end.

Do it as follows:

  1. public class Main {
  2. public static void main(String[] args) {
  3. // Tests
  4. System.out.println(simpleMultiplicationTable(2));
  5. System.out.println(simpleMultiplicationTable(3));
  6. }
  7. public static String simpleMultiplicationTable(int num) {
  8. StringBuilder sb = new StringBuilder();
  9. for (int i = 1; i &lt;= num; i++) {
  10. for (int j = 1; j &lt;= num; j++) {
  11. sb.append(i * j);
  12. if (j &lt; num) {
  13. sb.append(&quot; &quot;);
  14. }
  15. }
  16. if (i &lt; num) {
  17. sb.append(&quot;\n&quot;);
  18. }
  19. }
  20. return sb.toString();
  21. }
  22. }

Output:

  1. 1 2
  2. 2 4
  3. 1 2 3
  4. 2 4 6
  5. 3 6 9

Using String instead of StringBuilder:

  1. public class Main {
  2. public static void main(String[] args) {
  3. // Tests
  4. System.out.println(simpleMultiplicationTable(2));
  5. System.out.println(simpleMultiplicationTable(3));
  6. }
  7. public static String simpleMultiplicationTable(int num) {
  8. String table = &quot;&quot;;
  9. for (int i = 1; i &lt;= num; i++) {
  10. for (int j = 1; j &lt;= num; j++) {
  11. table += j &lt; num ? i * j + &quot; &quot; : i * j;
  12. }
  13. if (i &lt; num) {
  14. table = table + &quot;\n&quot;;
  15. }
  16. }
  17. return table;
  18. }
  19. }

JUnit Tests

  1. import static org.junit.Assert.assertEquals;
  2. import static org.junit.Assert.fail;
  3. import org.junit.jupiter.api.Test;
  4. class TestMethods {
  5. @Test
  6. public void testSimpleMultiplicationTable() {
  7. Table table = new Table();
  8. String result = table.simpleMultiplicationTable(2);
  9. if (result.contains(&quot; \n&quot;)) {
  10. fail(&quot;Your output table has one or more extra spaces before the newline character. You can use the trim() function to remove additional spaces&quot;);
  11. }
  12. assertEquals(&quot;1 2\n2 4&quot;, result);
  13. result = table.simpleMultiplicationTable(1);
  14. if (result.contains(&quot; \n&quot;)) {
  15. fail(&quot;Your output table has one or more extra spaces before the newline character. You can use the trim() function to remove additional spaces&quot;);
  16. }
  17. assertEquals(&quot;1&quot;, result);
  18. }
  19. }
  20. class Table {
  21. public String simpleMultiplicationTable(int num) {
  22. String table = &quot;&quot;;
  23. for (int i = 1; i &lt;= num; i++) {
  24. for (int j = 1; j &lt;= num; j++) {
  25. table += j &lt; num ? i * j + &quot; &quot; : i * j;
  26. }
  27. if (i &lt; num) {
  28. table = table + &quot;\n&quot;;
  29. }
  30. }
  31. return table;
  32. }
  33. }

huangapple
  • 本文由 发表于 2020年4月7日 08:14:19
  • 转载请务必保留本文链接：https://go.coder-hub.com/61070876.html
  • formatting
  • java
  • junit
  • nested-loops
  • string
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