Nested For & Text Patterns
Use nested for loops to print rectangles, right triangles, and small tables. Control rows (outer) and columns (inner).
Nested For & Text Patterns is a free Java Academy lesson on CoddyKit. This is lesson 2 of 3. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Java Academy learning path, and your progress syncs across the web and the CoddyKit app. The Java Academy course includes 3 lessons in total.
Nested Concept
Nested loops: a loop inside another loop. Often, the outer loop controls rows and the inner loop controls columns.
Rectangle 3x4
Rectangle 3x4
public class Main {
public static void main(String[] args) {
// Outer loop controls the number of rows (3 rows total)
for (int r = 1; r <= 3; r = r + 1) {
// Start with an empty string for each row
String line = "";
// Inner loop controls the number of columns (4 stars per row)
for (int c = 1; c <= 4; c = c + 1) {
// Add one star to the line in each iteration
line = line + "*";
}
// Print the completed line of stars
System.out.println(line);
}
}
}
Right Triangle
Right triangle
public class Main {
public static void main(String[] args) {
// Outer loop controls the number of rows (from 1 up to 4)
for (int r = 1; r <= 4; r = r + 1) {
// Start with an empty string for each row
String line = "";
// Inner loop runs 'r' times, so stars increase with each row
for (int c = 1; c <= r; c = c + 1) {
// Add one star to the current line
line = line + "*";
}
// Print the completed line of stars
System.out.println(line);
}
}
}
Right-Aligned
Right-aligned triangle: add spaces before stars.
public class Main {
public static void main(String[] args) {
int height = 4; // total number of rows for the triangle
// Outer loop: controls the row number
for (int r = 1; r <= height; r = r + 1) {
String line = "";
// First inner loop: add spaces so stars are right-aligned
for (int s = 1; s <= (height - r); s = s + 1) {
line = line + " ";
}
// Second inner loop: add stars according to current row
for (int c = 1; c <= r; c = c + 1) {
line = line + "*";
}
// Print the final line (spaces + stars)
System.out.println(line);
}
}
}
1..3 Table
Table 1..3
public class Main {
public static void main(String[] args) {
// Outer loop controls the rows (1 to 3)
for (int r = 1; r <= 3; r = r + 1) {
String line = "";
// Inner loop controls the columns (1 to 3)
for (int c = 1; c <= 3; c = c + 1) {
// Multiply row number (r) by column number (c)
// Add the result plus a space to the line
line = line + (r * c) + " ";
}
// Print the row after building it
System.out.println(line);
}
}
}
Patterns Demo
Run it: Three patterns printed without any console input.
public class Main {
public static void main(String[] args) {
// Rectangle 3x4
for (int r = 1; r <= 3; r = r + 1) {
String line = "";
for (int c = 1; c <= 4; c = c + 1) {
line = line + "*";
}
System.out.println(line);
}
// Right triangle
for (int r = 1; r <= 4; r = r + 1) {
String line = "";
for (int c = 1; c <= r; c = c + 1) {
line = line + "*";
}
System.out.println(line);
}
// Right-aligned triangle
int height = 4;
for (int r = 1; r <= height; r = r + 1) {
String line = "";
for (int s = 1; s <= (height - r); s = s + 1) {
line = line + " ";
}
for (int c = 1; c <= r; c = c + 1) {
line = line + "*";
}
System.out.println(line);
}
}
}
3x4 Rectangle
Quick check: Which snippet prints a 3x4 rectangle of * (3 rows, 4 columns)?
Recap & Next
Recap: You used nested loops for rectangles, triangles, alignment with spaces, and tiny tables.
Next: Practice and mini-challenges to build confidence with patterns.
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Frequently Asked Questions
Is the “Nested For & Text Patterns” lesson free?
Yes — the full text of “Nested For & Text Patterns” is free to read here on the web. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Java Academy course, upgrade to CoddyKit PRO. The Java Academy course includes 3 lessons in total.
What will I learn in “Nested For & Text Patterns”?
Use nested for loops to print rectangles, right triangles, and small tables. Control rows (outer) and columns (inner). You practise Java Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Java Academy?
No prior experience is required. Java Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 2 of 3.
How long does the “Nested For & Text Patterns” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Java Academy lesson?
Yes. Every Java Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- For Loop Basics
- Nested For & Text Patterns
- Pattern Practice & Mini-Challenges