Complete Java Star Patterns Guide

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📑 Table of Contents

CATEGORY A: Basic Patterns ⭐ Most Asked

1. Square Pattern
2. Hollow Square Pattern
3. Right Triangle Pattern
4. Left Triangle Pattern
5. Inverted Right Triangle
6. Inverted Left Triangle

CATEGORY B: Pyramid Patterns 🔥 Very Common

7. Pyramid Pattern
8. Inverted Pyramid Pattern
9. Hollow Pyramid Pattern
10. Diamond Pattern
11. Hollow Diamond Pattern
12. Half Diamond Pattern

CATEGORY C: Advanced Patterns 💎 Interview Favorites

13. Butterfly Pattern
14. Hourglass Pattern
15. Pascal's Triangle
16. Floyd's Triangle
17. Number Pyramid
18. Palindrome Pattern

CATEGORY D: Specialty Patterns ✨

19. Heart Pattern
20. Plus Pattern
21. Cross Pattern
22. Zig-Zag Pattern
23. Sandglass Pattern
24. Wave Pattern

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CATEGORY A: Basic Patterns ⭐

1. Square Pattern

Difficulty: Easy | Asked by: TCS, Wipro, Infosys

Output:

*****
*****
*****
*****
*****

Java Code:

public static void squarePattern(int n) {
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            System.out.print("* ");
        }
        System.out.println();
    }
}

Logic: Simple nested loop - outer for rows, inner for columns.

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2. Hollow Square Pattern

Difficulty: Easy | Asked by: Accenture, Cognizant

Output:

*****
*   *
*   *
*   *
*****

Java Code:

public static void hollowSquarePattern(int n) {
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            if (i == 0 || i == n - 1 || j == 0 || j == n - 1) {
                System.out.print("* ");
            } else {
                System.out.print("  ");
            }
        }
        System.out.println();
    }
}

Logic: Print stars only on borders (first/last row or first/last column).

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3. Right Triangle Pattern

Difficulty: Easy | Asked by: Amazon, Microsoft, Google

Output:

*
**
***
****
*****

Java Code:

public static void rightTrianglePattern(int n) {
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= i; j++) {
            System.out.print("* ");
        }
        System.out.println();
    }
}

Logic: Print stars equal to current row number.

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4. Left Triangle Pattern

Difficulty: Easy | Asked by: Adobe, Oracle

Output:

    *
   **
  ***
 ****
*****

Java Code:

public static void leftTrianglePattern(int n) {
    for (int i = 1; i <= n; i++) {
        // Print spaces
        for (int j = 1; j <= n - i; j++) {
            System.out.print(" ");
        }
        // Print stars
        for (int j = 1; j <= i; j++) {
            System.out.print("*");
        }
        System.out.println();
    }
}

Logic: Print (n - i) spaces, then i stars for each row i.

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5. Inverted Right Triangle

Difficulty: Easy | Asked by: Capgemini, IBM

Output:

*****
****
***
**
*

Java Code:

public static void invertedRightTriangle(int n) {
    for (int i = n; i >= 1; i--) {
        for (int j = 1; j <= i; j++) {
            System.out.print("* ");
        }
        System.out.println();
    }
}

Logic: Start from n and decrement, print stars equal to current value.

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6. Inverted Left Triangle

Difficulty: Easy | Asked by: HCL, Tech Mahindra

Output:

*****
 ****
  ***
   **
    *

Java Code:

public static void invertedLeftTriangle(int n) {
    for (int i = 0; i < n; i++) {
        // Print spaces
        for (int j = 0; j < i; j++) {
            System.out.print(" ");
        }
        // Print stars
        for (int j = 0; j < n - i; j++) {
            System.out.print("*");
        }
        System.out.println();
    }
}

Logic: Print i spaces, then (n - i) stars for each row i.

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CATEGORY B: Pyramid Patterns 🔥

7. Pyramid Pattern

Difficulty: Medium | Asked by: Amazon, Flipkart, Paytm

Output:

    *
   ***
  *****
 *******
*********

Java Code:

public static void pyramidPattern(int n) {
    for (int i = 0; i < n; i++) {
        // Print spaces
        for (int j = 0; j < n - i - 1; j++) {
            System.out.print(" ");
        }
        // Print stars
        for (int j = 0; j < 2 * i + 1; j++) {
            System.out.print("*");
        }
        System.out.println();
    }
}

Logic: Print (n - i - 1) spaces, then (2 * i + 1) stars.

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8. Inverted Pyramid Pattern

Difficulty: Medium | Asked by: Google, Facebook

Output:

*********
 *******
  *****
   ***
    *

Java Code:

public static void invertedPyramidPattern(int n) {
    for (int i = 0; i < n; i++) {
        // Print spaces
        for (int j = 0; j < i; j++) {
            System.out.print(" ");
        }
        // Print stars
        for (int j = 0; j < 2 * (n - i) - 1; j++) {
            System.out.print("*");
        }
        System.out.println();
    }
}

Logic: Print i spaces, then (2 * (n - i) - 1) stars.

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9. Hollow Pyramid Pattern

Difficulty: Medium | Asked by: Microsoft, Adobe

Output:

    *
   * *
  *   *
 *     *
*********

Java Code:

public static void hollowPyramidPattern(int n) {
    for (int i = 0; i < n; i++) {
        // Print spaces
        for (int j = 0; j < n - i - 1; j++) {
            System.out.print(" ");
        }
        // Print stars
        for (int j = 0; j < 2 * i + 1; j++) {
            if (j == 0 || j == 2 * i || i == n - 1) {
                System.out.print("*");
            } else {
                System.out.print(" ");
            }
        }
        System.out.println();
    }
}

Logic: Print stars only at boundaries and last row.

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10. Diamond Pattern

Difficulty: Medium | Asked by: Amazon, Microsoft, Google

Output:

    *
   ***
  *****
 *******
*********
 *******
  *****
   ***
    *

Java Code:

public static void diamondPattern(int n) {
    // Upper pyramid
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n - i - 1; j++) {
            System.out.print(" ");
        }
        for (int j = 0; j < 2 * i + 1; j++) {
            System.out.print("*");
        }
        System.out.println();
    }

    // Lower inverted pyramid
    for (int i = n - 2; i >= 0; i--) {
        for (int j = 0; j < n - i - 1; j++) {
            System.out.print(" ");
        }
        for (int j = 0; j < 2 * i + 1; j++) {
            System.out.print("*");
        }
        System.out.println();
    }
}

Logic: Combine pyramid and inverted pyramid.

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11. Hollow Diamond Pattern

Difficulty: Hard | Asked by: Oracle, SAP

Output:

    *
   * *
  *   *
 *     *
*       *
 *     *
  *   *
   * *
    *

Java Code:

public static void hollowDiamondPattern(int n) {
    // Upper half
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n - i - 1; j++) {
            System.out.print(" ");
        }
        for (int j = 0; j < 2 * i + 1; j++) {
            if (j == 0 || j == 2 * i) {
                System.out.print("*");
            } else {
                System.out.print(" ");
            }
        }
        System.out.println();
    }

    // Lower half
    for (int i = n - 2; i >= 0; i--) {
        for (int j = 0; j < n - i - 1; j++) {
            System.out.print(" ");
        }
        for (int j = 0; j < 2 * i + 1; j++) {
            if (j == 0 || j == 2 * i) {
                System.out.print("*");
            } else {
                System.out.print(" ");
            }
        }
        System.out.println();
    }
}

Logic: Hollow pyramid + hollow inverted pyramid.

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12. Half Diamond Pattern

Difficulty: Medium | Asked by: Infosys, TCS

Output:

*
**
***
****
*****
****
***
**
*

Java Code:

public static void halfDiamondPattern(int n) {
    // Upper half
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= i; j++) {
            System.out.print("*");
        }
        System.out.println();
    }

    // Lower half
    for (int i = n - 1; i >= 1; i--) {
        for (int j = 1; j <= i; j++) {
            System.out.print("*");
        }
        System.out.println();
    }
}

Logic: Right triangle + inverted right triangle.

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CATEGORY C: Advanced Patterns 💎

13. Butterfly Pattern

Difficulty: Hard | Asked by: Amazon, Google, Microsoft

Output:

*        *
**      **
***    ***
****  ****
**********
****  ****
***    ***
**      **
*        *

Java Code:

public static void butterflyPattern(int n) {
    // Upper half
    for (int i = 1; i <= n; i++) {
        // Left stars
        for (int j = 1; j <= i; j++) {
            System.out.print("*");
        }
        // Spaces
        for (int j = 1; j <= 2 * (n - i); j++) {
            System.out.print(" ");
        }
        // Right stars
        for (int j = 1; j <= i; j++) {
            System.out.print("*");
        }
        System.out.println();
    }

    // Lower half
    for (int i = n - 1; i >= 1; i--) {
        // Left stars
        for (int j = 1; j <= i; j++) {
            System.out.print("*");
        }
        // Spaces
        for (int j = 1; j <= 2 * (n - i); j++) {
            System.out.print(" ");
        }
        // Right stars
        for (int j = 1; j <= i; j++) {
            System.out.print("*");
        }
        System.out.println();
    }
}

Logic: Mirror two triangles with spaces in between.

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14. Hourglass Pattern

Difficulty: Hard | Asked by: Adobe, Oracle

Output:

*********
 *******
  *****
   ***
    *
   ***
  *****
 *******
*********

Java Code:

public static void hourglassPattern(int n) {
    // Upper inverted pyramid
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < i; j++) {
            System.out.print(" ");
        }
        for (int j = 0; j < 2 * (n - i) - 1; j++) {
            System.out.print("*");
        }
        System.out.println();
    }

    // Lower pyramid (skip middle line)
    for (int i = 1; i < n; i++) {
        for (int j = 0; j < n - i - 1; j++) {
            System.out.print(" ");
        }
        for (int j = 0; j < 2 * i + 1; j++) {
            System.out.print("*");
        }
        System.out.println();
    }
}

Logic: Inverted pyramid + pyramid (skip center).

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15. Pascal's Triangle

Difficulty: Hard | Asked by: Google, Facebook, Amazon

Output:

    1
   1 1
  1 2 1
 1 3 3 1
1 4 6 4 1

Java Code:

public static void pascalsTriangle(int n) {
    for (int i = 0; i < n; i++) {
        // Print spaces
        for (int j = 0; j < n - i - 1; j++) {
            System.out.print(" ");
        }

        int num = 1;
        for (int j = 0; j <= i; j++) {
            System.out.print(num + " ");
            num = num * (i - j) / (j + 1);
        }
        System.out.println();
    }
}

Logic: Use binomial coefficient formula: C(n,k) = C(n,k-1) * (n-k+1) / k

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16. Floyd's Triangle

Difficulty: Medium | Asked by: TCS, Infosys, Wipro

Output:

1
2 3
4 5 6
7 8 9 10
11 12 13 14 15

Java Code:

public static void floydsTriangle(int n) {
    int num = 1;
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= i; j++) {
            System.out.print(num + " ");
            num++;
        }
        System.out.println();
    }
}

Logic: Print consecutive numbers in triangular form.

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17. Number Pyramid

Difficulty: Medium | Asked by: Amazon, Microsoft

Output:

    1
   121
  12321
 1234321
123454321

Java Code:

public static void numberPyramid(int n) {
    for (int i = 1; i <= n; i++) {
        // Print spaces
        for (int j = 1; j <= n - i; j++) {
            System.out.print(" ");
        }

        // Print ascending numbers
        for (int j = 1; j <= i; j++) {
            System.out.print(j);
        }

        // Print descending numbers
        for (int j = i - 1; j >= 1; j--) {
            System.out.print(j);
        }
        System.out.println();
    }
}

Logic: Print ascending then descending numbers.

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18. Palindrome Pattern

Difficulty: Medium | Asked by: Cognizant, Accenture

Output:

    1
   212
  32123
 4321234
543212345

Java Code:

public static void palindromePattern(int n) {
    for (int i = 1; i <= n; i++) {
        // Print spaces
        for (int j = 1; j <= n - i; j++) {
            System.out.print(" ");
        }

        // Print descending numbers
        for (int j = i; j >= 1; j--) {
            System.out.print(j);
        }

        // Print ascending numbers (skip 1)
        for (int j = 2; j <= i; j++) {
            System.out.print(j);
        }
        System.out.println();
    }
}

Logic: Print descending then ascending numbers.

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CATEGORY D: Specialty Patterns ✨

19. Heart Pattern

Difficulty: Hard | Asked by: Rare, but popular

Output:

 ***   ***
***** *****
 ***********
  *********
   *******
    *****
     ***
      *

Java Code:

public static void heartPattern(int n) {
    // Upper part
    for (int i = n / 2; i < n; i += 2) {
        // Left spaces
        for (int j = 1; j < n - i; j += 2) {
            System.out.print(" ");
        }
        // Left stars
        for (int j = 1; j <= i; j++) {
            System.out.print("*");
        }
        // Middle spaces
        for (int j = 1; j <= n - i; j++) {
            System.out.print(" ");
        }
        // Right stars
        for (int j = 1; j <= i; j++) {
            System.out.print("*");
        }
        System.out.println();
    }

    // Lower inverted pyramid
    for (int i = n; i > 0; i--) {
        for (int j = 0; j < n - i; j++) {
            System.out.print(" ");
        }
        for (int j = 1; j <= i * 2 - 1; j++) {
            System.out.print("*");
        }
        System.out.println();
    }
}

Logic: Two curves at top + inverted pyramid at bottom.

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20. Plus Pattern

Difficulty: Easy | Asked by: Accenture

Output:

  *
  *
*****
  *
  *

Java Code:

public static void plusPattern(int n) {
    int mid = n / 2;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            if (i == mid || j == mid) {
                System.out.print("*");
            } else {
                System.out.print(" ");
            }
        }
        System.out.println();
    }
}

Logic: Print stars at middle row or middle column.

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21. Cross Pattern

Difficulty: Easy | Asked by: Capgemini

Output:

*   *
 * *
  *
 * *
*   *

Java Code:

public static void crossPattern(int n) {
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            if (i == j || i + j == n - 1) {
                System.out.print("*");
            } else {
                System.out.print(" ");
            }
        }
        System.out.println();
    }
}

Logic: Print stars on main diagonal and anti-diagonal.

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22. Zig-Zag Pattern

Difficulty: Medium | Asked by: Oracle

Output:

  *   *
 * * * *
*   *   *

Java Code:

public static void zigZagPattern(int n) {
    for (int i = 0; i < 3; i++) {
        for (int j = 0; j < n; j++) {
            if (((i + j) % 4 == 0) || (i == 2 && j % 4 == 0)) {
                System.out.print("*");
            } else {
                System.out.print(" ");
            }
        }
        System.out.println();
    }
}

Logic: Use modulo arithmetic for wave positions.

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23. Sandglass Pattern

Difficulty: Hard | Asked by: IBM

Output:

*********
 *     *
  *   *
   * *
    *
   * *
  *   *
 *     *
*********

Java Code:

public static void sandglassPattern(int n) {
    // Upper part
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < i; j++) {
            System.out.print(" ");
        }
        for (int j = 0; j < 2 * (n - i) - 1; j++) {
            if (i == 0 || j == 0 || j == 2 * (n - i) - 2) {
                System.out.print("*");
            } else {
                System.out.print(" ");
            }
        }
        System.out.println();
    }

    // Lower part
    for (int i = n - 2; i >= 0; i--) {
        for (int j = 0; j < i; j++) {
            System.out.print(" ");
        }
        for (int j = 0; j < 2 * (n - i) - 1; j++) {
            if (i == 0 || j == 0 || j == 2 * (n - i) - 2) {
                System.out.print("*");
            } else {
                System.out.print(" ");
            }
        }
        System.out.println();
    }
}

Logic: Hollow inverted pyramid + hollow pyramid.

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24. Wave Pattern

Difficulty: Medium | Asked by: Tech Mahindra

Output:

  *   *   *
 * * * * * *
*   *   *   *

Java Code:

public static void wavePattern(int rows, int cols) {
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            if ((i + j) % 4 == 0 || (i == 2 && j % 2 == 0) ||
                (i == 1 && (j % 2 == 1))) {
                System.out.print("*");
            } else {
                System.out.print(" ");
            }
        }
        System.out.println();
    }
}

Logic: Create wave effect using modulo calculations.

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🎯 Main Method - Test All Patterns

public class StarPatternsDemo {
    public static void main(String[] args) {
        int n = 5; // Default size

        System.out.println("=== CATEGORY A: BASIC PATTERNS ===");
        squarePattern(n);
        hollowSquarePattern(n);
        rightTrianglePattern(n);
        leftTrianglePattern(n);
        invertedRightTriangle(n);
        invertedLeftTriangle(n);

        System.out.println("\n=== CATEGORY B: PYRAMID PATTERNS ===");
        pyramidPattern(n);
        invertedPyramidPattern(n);
        hollowPyramidPattern(n);
        diamondPattern(n);
        hollowDiamondPattern(n);
        halfDiamondPattern(n);

        System.out.println("\n=== CATEGORY C: ADVANCED PATTERNS ===");
        butterflyPattern(n);
        hourglassPattern(n);
        pascalsTriangle(n);
        floydsTriangle(n);
        numberPyramid(n);
        palindromePattern(n);

        System.out.println("\n=== CATEGORY D: SPECIALTY PATTERNS ===");
        heartPattern(6);
        plusPattern(n);
        crossPattern(n);
        zigZagPattern(20);
        sandglassPattern(n);
        wavePattern(3, 20);
    }
}

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📚 Quick Tips for Interviews

1. Understand the Logic First: Draw the pattern on paper and identify the logic for spaces and stars.

2. Common Approach: Most patterns use nested loops:

   • Outer loop for rows
   • Inner loop(s) for columns, spaces, and stars

3. Formula Patterns:

   • Right triangle: stars = row number
   • Pyramid: spaces = (n - i - 1), stars = (2 * i + 1)
   • Diamond: Combine pyramid + inverted pyramid

4. Practice These Most:

   • Right Triangle
   • Pyramid
   • Diamond
   • Butterfly
   • Number patterns

5. Time Complexity: Most patterns are O(n²)

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🏆 Company-Wise Most Asked

• Amazon, Google, Microsoft: Pyramid, Diamond, Butterfly
• TCS, Infosys, Wipro: Floyd's Triangle, Pascal's Triangle, Basic patterns
• Accenture, Cognizant: Hollow patterns, Number patterns
• Adobe, Oracle: Complex combinations, Hourglass

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Pro Tip: Master the basic patterns first, then combine them to create complex patterns!