The Upper Star Triangle Pattern is a simple Java pattern-printing program in which each row contains one more star than the previous row. It is commonly used to practice nested loops, spacing, and pattern generation.
- Leading spaces decrease as the row number increases.
- Useful for learning nested loops and pattern logic.
Illustration
Input: Rows = 5
Output: *
**
***
****
*****
Approach
- Initialize the number of rows.
- Use an outer loop to print each row.
- Print the required leading spaces.
- Print stars equal to the current row number.
- Move to the next line.
Example: Upper Part
// Importing input output classes
import java.io.*;
// Main Class
class GFG {
// Method 1
// To print upper part of the pattern
private static void displayUpperPart(int size)
{
// Declaring variables for rows and columns
// respectively
int m, n;
// Outer loop for rows
for (m = size - 1; m >= 0; m--) {
// Inner loop 1
// to print triangle 1
for (n = 0; n < m; n++) {
// Printing whitespace
System.out.print(" ");
}
// Inner loop 2
// to print triangle 2
for (n = m; n <= size - 1; n++) {
// Printing star with whitespace
System.out.print("*"
+ " ");
}
// By now done with one row so next line
System.out.println();
}
}
// Method 2
// Main driver method
public static void main(String[] args)
{
// Declaring and initializing variables to
// size of the triangle
int size = 7;
// Calling the above Method 1 to
// print and display the upper part of triangle
displayUpperPart(size);
}
}
Output
*
* *
* * *
* * * *
* * * * *
* * * * * *
* * * * * * *
Explanation: The outer loop controls the number of rows. The first inner loop prints the leading spaces, while the second inner loop prints stars equal to the current row number, forming an upper star triangle.
Example: Lower Part of the triangleÂ
// Importing input output classes
import java.io.*;
// Main Class
class GFG {
// Method 1
// To print lower part of the pattern
private static void displayLowerPart(int size)
{
// Declaring variables for rows and columns
// respectively
int m, n;
// Outer loop fo Rows
for (m = 1; m <= size; m++) {
// Inner loop 1 to print triangle 3
for (n = 1; n < m; n++) {
// Printing whitespace
System.out.print(" ");
}
// Inner loop 2 to print triangle 4
for (n = m; n <= size; n++) {
// Printing star and whitespace
System.out.print("*"
+ " ");
}
// By now done with one row so new line
System.out.println();
}
}
// Method 2
// Main driver method
public static void main(String[] args)
{
// Declaring and initializing variable to
// size of the triangle
// This is number of rows
int size = 7;
// Calling the above Method1
// to display lower part of the triangle
displayLowerPart(size);
}
}
Output
* * * * * * *
* * * * * *
* * * * *
* * * *
* * *
* *
*
 Example: Complete Mirror Upper Star Triangle Pattern
// Importing input output classes
import java.io.*;
// Main Class
public class GFG {
// Method 1
// To print upper part of the pattern
private static void displayUpperPart(int size)
{
// Declaring variables for rows and columns
// respectively
int m, n;
// Outer loop for rows
for (m = size - 1; m >= 0; m--) {
// Inner loop 1
for (n = 0; n < m; n++) {
// Printing whitespace
System.out.print(" ");
}
// Inner loop 2
for (n = m; n <= size - 1; n++) {
// Printing star with whitespace
System.out.print("*"
+ " ");
}
// By now we are done with one row so new line
System.out.println();
}
}
// Method 2
// To print lower part of the pattern
private static void displayLowerPart(int size)
{
// Declaring variables for rows and columns
// respectively
int m, n;
// Outer loop for rows
for (m = 1; m <= size; m++) {
// Inner loop 1
for (n = 1; n < m; n++) {
// Printing whitespace
System.out.print(" ");
}
// Inner loop 2
for (n = m; n <= size; n++) {
// Printing star and whitespace
System.out.print("*"
+ " ");
}
// By now we are done with one row so new line
System.out.println();
}
}
// Method 3
// Main driver method
public static void main(String[] args)
{
// Declaring and initializing variable to
// size of the triangle
int size = 7;
// Calling Method 1 to
// display the upper part
displayUpperPart(size);
// Calling Method 2 to
// display lower part
displayLowerPart(size);
}
}
Output
*
* *
* * *
* * * *
* * * * *
* * * * * *
* * * * * * *
* * * * * * *
* * * * * *
* * * * *
* * * *
* * *
* *
*
