Nested for loops

A for loop inside a for loop is called a nested for loop. Sometimes this is the right tool for the job. Here's an example where you print out a multiplication table. Notice that we set the Maximum number if iterations as a variable. You could even prompt the user for this value making the for loop even more flexible.

Example: Print out the multiplication table.

public class MultiplicationTable {
  static final int MAX = 10;

  public static void main (String[] args) {
    int row, column;

    for (row = 1; row <= MAX; row++) {
      for (column = 1; column <= MAX; column++)
      {
          System.out.print(row * column + "\t");
      }
      System.out.println();//Takes us to the next line
    }
  }
}

Table generated from the program

1   2    3    4    5    6    7    8    9    10    
2    4    6    8    10    12    14    16    18    20    
3    6    9    12    15    18    21    24    27    30    
4    8    12    16    20    24    28    32    36    40    
5    10    15    20    25    30    35    40    45    50    
6    12    18    24    30    36    42    48    54    60    
7    14    21    28    35    42    49    56    63    70    
8    16    24    32    40    48    56    64    72    80    
9    18    27    36    45    54    63    72    81    90    
10    20    30    40    50    60    70    80    90    100    

Your assignment

1. Create a program to print the lower-case characters from the ASCII table. They range from 97 to 127. To print a numeric value such as 97 into a lower case 'a' cast it to a char: System.out.println(c + ": " + (char)c);

   a
   b
   c
   d
   ...
   z
   

2. Modify the program above so it prints all the capital letters and all the lower case letters.

3. Create a nested loop to print the outline format as shown below. The outer loop would contain numbers the inner loop would contain letters. To print lower case letters from a loop

1. XXX
   a. xxx
   b. xxx
   c. xxx
2. XXX
   a. xxx
   b. xxx
   c. xxx
3. XXX
   a. xxx
   b. xxx
   c. xxx
4. XXX
   a. xxx
   b. xxx
   c. xxx
5. XXX
   a. xxx
   b. xxx
   c. xxx