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bala d kaveri
bala d kaveri

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🚀 Day 28 of My Automation Journey – Nested For Loop

#loops #java #automation #beginners

Today’s learning was super important 👇

👉 Moving from single loops → nested loops
👉 This is where pattern logic begins 🔥

🔹 1. What is a Nested Loop?

👉 A loop inside another loop is called a nested loop

💡 Structure: 

for(row) {
    for(column) {
        // logic
    }
}
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🧠 How It Works

👉 Outer loop → controls rows
👉 Inner loop → controls columns

🔹 2. Basic Example (Print 1’s) 

for(int row = 1; row <= 2; row++) {
    for(int col = 1; col <= 5; col++) {
        System.out.print(1);
    }
    System.out.println();
}
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📤 Output: 

11111
11111
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🔹 3. Print Row Number 

for(int row = 1; row <= 2; row++) {
    for(int col = 1; col <= 5; col++) {
        System.out.print(row);
    }
    System.out.println();
}
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📤 Output: 

11111
22222
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🔹 4. Print Column Number 

for(int row = 1; row <= 2; row++) {
    for(int col = 1; col <= 5; col++) {
        System.out.print(col);
    }
    System.out.println();
}
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📤 Output: 

12345
12345
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🔹 5. Rectangle Pattern ⭐ 

for(int row = 1; row <= 3; row++) {
    for(int col = 1; col <= 5; col++) {
        System.out.print("*");
    }
    System.out.println();
}
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📤 Output: 

*****
*****
*****
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🔹 6. Reverse Triangle Pattern 🔻 

int count = 5;

for(int row = 1; row <= 5; row++) {
    for(int col = 1; col <= count; col++) {
        System.out.print("*");
    }
    System.out.println();
    count--;
}
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📤 Output: 

*****
****
***
**
*
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🔹 7. Triangle Pattern 🔺 

int count = 1;

for(int row = 1; row <= 5; row++) {
    for(int col = 1; col <= count; col++) {
        System.out.print("*");
    }
    System.out.println();
    count++;
}
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📤 Output: 

*
**
***
****
*****
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🔍 Key Concept (Very Important 🔥)

👉 Inner loop runs completely for each outer loop iteration

Example:

  • Row 1 → full columns execute
  • Row 2 → full columns execute again

⚠️ Common Mistake

👉 Forgetting System.out.println();

System.out.print("*"); // stays in same line
System.out.println();  // moves to next line
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🔹 Real Understanding Trick 💡

Think like a table:

Row Columns Execution
1 1 → 5
2 1 → 5

👉 That’s how patterns are built

🔚 Final Takeaways

✔ Nested loop = loop inside loop
✔ Outer loop → rows
✔ Inner loop → columns
✔ Used for pattern problems
✔ Base for advanced logic

💡 Golden Insight

👉 If you understand nested loops, you unlock pattern programming 🔓

🤖 A Small Note
I used ChatGPT to help structure and refine this blog while keeping the concepts aligned with my learning.

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