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Print Repeated Number Pattern in Java

beginner· Patterns · Number Patterns

Problem

Instead of counting up through a row like a plain number triangle, this pattern holds one fixed value per row — the row number itself — and repeats only that.

Given a number of rows, print a triangle where row i consists of the number i repeated i times.

Input

5

Output

Java Program

Java

public class RepeatedNumberPattern {
    public static void main(String[] args) {
        int n = 5;

        for (int i = 1; i <= n; i++) {
            StringBuilder row = new StringBuilder();
            for (int j = 0; j < i; j++) {
                if (j > 0) row.append(" ");
                row.append(i); // same value repeated across the whole row
            }
            System.out.println(row);
        }
    }
}

▶ Run Code

Output

Core Logic

Printing the row index itself, i times per row, builds a growing triangle without ever incrementing the value being printed.

How It Works

1The outer loop runs i from 1 to n, one row per value of i.
2The inner loop runs exactly i times, printing i itself on every pass — not a counter that changes.
3Each row therefore shows a single number repeated, rather than a run of consecutive numbers.
4Row width still grows by one each time, the same shape as any other increasing triangle.

Row 4 repeats the value 4 across all four positions: 4 4 4 4.

💡

Key Point: This differs from Number Triangle, which counts 1 through i across a row — here every position in a row holds the exact same value, the row number itself.

Complexity

Time Complexity: O(n²)Space Complexity: O(1)

Why: The total values printed across every row grows proportionally to n², with only the two loop counters kept in memory.

Key Concepts

nested for loopfixed row value

Approach 2: Java 8

Java

import java.util.stream.Collectors;
import java.util.stream.IntStream;

public class RepeatedNumberPatternStream {
    public static void main(String[] args) {
        int n = 5;
        IntStream.rangeClosed(1, n)
            .mapToObj(i -> IntStream.range(0, i)
                .mapToObj(j -> String.valueOf(i)) // ignores j, always yields the row's own value
                .collect(Collectors.joining(" ")))
            .forEach(System.out::println);
    }
}

▶ Run Code

Output

Core Logic

Mapping every position in a row to the same fixed row value, rather than to the position itself, is what tells the stream to repeat instead of count.

How It Works

1IntStream.rangeClosed(1, n) generates one stream element per row.
2For each row i, an inner IntStream.range(0, i) generates i positions.
3.mapToObj(j -> String.valueOf(i)) ignores the position j entirely and always yields i.
4Collectors.joining(" ") joins that row's repeated values before forEach prints it.

For row 4, the inner stream produces four elements, but every one of them maps to "4", giving "4 4 4 4".

💡

Key Point: The inner stream's position variable j is generated but never used in the mapping — it only controls how many times the row value repeats.

Complexity

Time Complexity: O(n²)Space Complexity: O(1)

Why: The nested streams still produce one value per grid position across all rows, proportional to n², without collecting the full triangle.

Print Repeated Number Pattern in Java

Problem

Java Program

Output

Core Logic

Key Concepts

Approach 2: Java 8

Output

Core Logic

Key Concepts

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