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Java Academy · Lesson

Pattern Practice & Mini-Challenges

Practice nested loop patterns: hollow rectangles, centered pyramids, and diagonals. Tackle mini-challenges step by step.

Pattern Tips

Tips for text patterns:

  • Outer loop controls rows
  • Inner loop builds each row
  • Append characters to a String then print once
  • Use conditions to choose star or space

Hollow Rectangle

Hollow rectangle 3x5

public class Main {
  public static void main(String[] args) {
    // Outer loop: goes through each row (1 to 3)
    for (int r = 1; r <= 3; r = r + 1) {
      String line = "";

      // Inner loop: goes through each column (1 to 5)
      for (int c = 1; c <= 5; c = c + 1) {
        // Print a star if we are on:
        // - the first row (r == 1)
        // - the last row (r == 3)
        // - the first column (c == 1)
        // - the last column (c == 5)
        if (r == 1 || r == 3 || c == 1 || c == 5) {
          line = line + "*";
        } else {
          // Otherwise, print a space (inside of the rectangle)
          line = line + " ";
        }
      }

      // Print the completed row
      System.out.println(line);
    }
  }
}

All lessons in this course

  1. For Loop Basics
  2. Nested For & Text Patterns
  3. Pattern Practice & Mini-Challenges
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