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🔁 Java Type Casting – Convert Between Data Type

In Java, sometimes you’ll need to convert one data type to another — like changing an int to a float, or a double to an int.

This is called Type Casting, and it comes in two flavors:

Type	Description	Also Called
Widening Cast	Smaller to larger type (automatic)	Implicit casting
Narrowing Cast	Larger to smaller type (manual)	Explicit casting

Let’s explore both — GoNimbus style.

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🔓 1. Widening Casting (Automatic / Safe)

✅ Java does this for you automatically when you assign a smaller type to a larger type — because there’s no data loss.

🔁 Order of Widening:

byte → short → int → long → float → double

Example:

public class WideningExample {
  public static void main(String[] args) {
    int num = 100;
    double result = num;  // int → double (automatic)
    System.out.println("Result: " + result);  // Output: 100.0
  }
}

🧠 Why it works: A double can easily hold an int value without losing precision.

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🔐 2. Narrowing Casting (Manual / Risky)

⛔ This must be done manually because you might lose data or precision when converting from a larger type to a smaller one.

Example:

public class NarrowingExample {
  public static void main(String[] args) {
    double price = 99.99;
    int roundedPrice = (int) price;  // double → int (manual)
    System.out.println("Rounded: " + roundedPrice);  // Output: 99
  }
}

⚠️ The decimal .99 is cut off, not rounded — casting simply truncates the value.

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🔎 Real-World Example: Invoice Round-Off

public class InvoiceDemo {
  public static void main(String[] args) {
    double billAmount = 1234.75;
    int payable = (int) billAmount; // Remove decimals

    System.out.println("Original Amount: ₹" + billAmount);
    System.out.println("Payable Amount: ₹" + payable);
  }
}

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⚖️ Widening vs Narrowing – Quick Summary

Cast Type	From → To	Automatic?	Risk of Data Loss
Widening	int → double	✅ Yes	❌ No
Narrowing	double → int	❌ No	✅ Yes

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💬 GoNimbus Pro Tips

✅ Use widening when possible — it’s safe
✅ Always test narrowing conversions for data loss
✅ When converting user inputs (like strings to numbers), use Integer.parseInt() or Double.parseDouble()
✅ Avoid unnecessary casts to keep your code clean

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