A diamond star pattern is formed by combining an upper pyramid and an inverted pyramid. The number of stars increases gradually until the middle row and then decreases symmetrically, creating a diamond shape.
- The number of stars increases to the middle row and then decreases symmetrically.
- Leading spaces maintain proper alignment of the pattern.
Illustration
Input: number = 7
Output:
Approach
To print a diamond pattern:
- Print the upper half by increasing the number of stars in each row.
- Print the required leading spaces before the stars.
- Print the lower half by decreasing the number of stars.
- Use nested loops to control spaces and stars.
Method 1: Using for Loop
// Importing input output classes
import java.io.*;
// Main class
public class GFG {
// Main driver method
public static void main(String[] args)
{
// Declaring and initializing variables
// Variable initialized to the row where max star
// should be there as after that they decreases to
// give diamond pattern
int number = 7;
// Diamond starting with single star in first row,so
// initialized
int m = 1;
// Columnar printing
int n;
// Outer loop 1
// Prints the first half diamond
do {
n = 1;
// Inner loop 1
// Prints space until ++n <= number - m + 1 is
// false
do {
// Print whitespace between
System.out.print(" ");
}
// Condition for inside do-while loop 1
while (++n <= number - m + 1);
// Now
n = 1;
// Inner loop 2
// Prints star until ++n <= m * 2 - 1 is false
do {
// Print star
System.out.print("*");
}
// Condition for inner do-while loop 2
while (++n <= m * 2 - 1);
// A new row requires a new line
System.out.println();
}
// Condition for outer do-while loop 1
while (++m <= number);
// Now we are done with printing the upper half
// diamond.
// Note: Not to print the bottom row again in lower
// half diamond printing Hence variable to be
// initialized should one lesser than number
m = number - 1;
// Outer loop 2
// Prints the second half diamond
do {
n = 1;
// Inner loop 1
// Prints space until ++n <= number - m + 1 is
// false
do {
// Print whitespace between
System.out.print(" ");
} while (++n <= number - m + 1);
n = 1;
// Inner loop 2
// Prints star until ++n <= m * 2 - 1 is false
do {
// Prints star
System.out.print("*");
} while (++n <= m * 2 - 1);
// By now done with one row of lower diamond
// printing so a new line is required
System.out.println();
}
// Condition for outer do-while loop 2
while (--m > 0);
}
}
Output
*
***
*****
*******
*********
***********
*************
***********
*********
*******
*****
***
*
Explanation: The first set of loops prints the upper pyramid by increasing the number of stars in each row. The second set prints the inverted pyramid by decreasing the number of stars. Together, both halves form a symmetric diamond.
Method 2: Using while Loop
// Importing input output classes
import java.io.*;
// Main class
public class GFG {
// Main driver method
public static void main(String[] args)
{
// Declaring and initializing variables
// Variable initialized to the row where max star
// should be there as after that they decreases to
// give diamond pattern
int number = 7;
// Diamond starting with single star in first row
int m = 1;
// Columnar printing
int n;
// Outer loop 1
// Prints the first half diamond
// Condition holding true till
// number of rows initialized
while (m <= number) {
n = 1;
// Inner loop 1
// Prints space until n++ <= number - m is false
while (n++ <= number - m) {
// Print whitespaces inbetween
System.out.print(" ");
}
n = 1;
// Inner loop 2
// Prints star until n++ <= m * 2 - 1 is false
while (n++ <= m * 2 - 1) {
// Print star
System.out.print("*");
}
// By now we are done for above pyramid printing
// ending line after each row
System.out.println();
// Incrementing as we want pyramid generation
m++;
}
// Now we are done with printing the upper half
// diamond.
// Note: Not to print the bottom row again in lower
// half diamond printing Hence variable t be
// initialized should one lesser than number
m = number - 1;
// Outer loop 2
// Prints the second half diamond
while (m > 0) {
n = 1;
// Inner loop 1
// Prints spaces until n++ <= number - m is
// false
while (n++ <= number - m) {
// Print whitespace in between
System.out.print(" ");
}
n = 1;
// Inner loop 2
// Prints star until n++ <= m * 2 - 1 is false
while (n++ <= m * 2 - 1) {
// Print star
System.out.print("*");
}
// Ending line after each row
System.out.println();
// Decrementing as we want reverse pyramid
// generation
m--;
}
}
}
Output
*
***
*****
*******
*********
***********
*************
***********
*********
*******
*****
***
*
Explanation: The while loops first generate the upper pyramid and then the lower inverted pyramid. Separate loops are used to print spaces and stars, ensuring the diamond remains properly aligned.
Method 3: Using do-while Loop
// Importing input output classes
import java.io.*;
// Main class
public class GFG {
// Main driver method
public static void main(String[] args)
{
// Declaring and initializing variables
// Variable initialized to the row where max star
// should be there as after that they decreases to
// give diamond pattern
int number = 7;
int m, n;
// Outer loop 1
// prints the first half diamond
for (m = 1; m <= number; m++) {
// Inner loop 1 print whitespaces inbetween
for (n = 1; n <= number - m; n++) {
System.out.print(" ");
}
// Inner loop 2 prints star
for (n = 1; n <= m * 2 - 1; n++) {
System.out.print("*");
}
// Ending line after each row
System.out.println();
}
// Outer loop 2
// Prints the second half diamond
for (m = number - 1; m > 0; m--) {
// Inner loop 1 print whitespaces inbetween
for (n = 1; n <= number - m; n++) {
System.out.print(" ");
}
// Inner loop 2 print star
for (n = 1; n <= m * 2 - 1; n++) {
System.out.print("*");
}
// Ending line after each row
System.out.println();
}
}
}
Output
*
***
*****
*******
*********
***********
*************
***********
*********
*******
*****
***
*
Explanation: The do-while loop executes at least once for every row. It first prints the upper pyramid and then the lower pyramid, using nested do-while loops to print spaces and stars, resulting in a complete diamond pattern.