Widening and Narrowing Type Casting & Type Safety0%

Widening and Narrowing Type Casting & Type Safety

Beginner12 min read•Updated: 2026-10-22

🔄 Widening and Narrowing Type Casting & Type Safety

Introduction

Type casting is the process of converting a value from one primitive data type into another. In Java, type conversions are categorized into Widening (Automatic) and Narrowing (Explicit).

📈 1. Widening Casting (Implicit / Automatic)

Converting a smaller data type to a larger data type is performed automatically by the Java compiler because no data loss can occur:

1byte ──► short ──► int ──► long ──► float ──► double

📉 2. Narrowing Casting (Explicit / Manual)

Converting a larger data type to a smaller data type requires explicit casting syntax (targetType)value because data truncation or loss can occur:

1public class NarrowingDemo {
2    public static void main(String[] args) {
3        double exactFee = 4999.85;
4 
5        // Explicit cast truncates fractional part:
6        int roundedFee = (int) exactFee; // Becomes 4999
7 
8        System.out.println("Original: " + exactFee);
9        System.out.println("Narrowed: " + roundedFee);
10 
11        // Overflow example:
12        int bigNumber = 130;
13        byte smallByte = (byte) bigNumber; // Wraps around to -126 due to 8-bit two's complement!
14        System.out.println("Overflowed byte: " + smallByte);
15    }
16}

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Type Inference with var (Java 10+)

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Type Inference with var (Java 10+)

Widening and Narrowing Type Casting & Type Safety

Beginner12 min read•Updated: 2026-10-22

Study Materials

🔄 Widening and Narrowing Type Casting & Type Safety

Introduction

Type casting is the process of converting a value from one primitive data type into another. In Java, type conversions are categorized into Widening (Automatic) and Narrowing (Explicit).

📈 1. Widening Casting (Implicit / Automatic)

Converting a smaller data type to a larger data type is performed automatically by the Java compiler because no data loss can occur:

1byte ──► short ──► int ──► long ──► float ──► double

📉 2. Narrowing Casting (Explicit / Manual)

Converting a larger data type to a smaller data type requires explicit casting syntax (targetType)value because data truncation or loss can occur:

1public class NarrowingDemo {
2    public static void main(String[] args) {
3        double exactFee = 4999.85;
4 
5        // Explicit cast truncates fractional part:
6        int roundedFee = (int) exactFee; // Becomes 4999
7 
8        System.out.println("Original: " + exactFee);
9        System.out.println("Narrowed: " + roundedFee);
10 
11        // Overflow example:
12        int bigNumber = 130;
13        byte smallByte = (byte) bigNumber; // Wraps around to -126 due to 8-bit two's complement!
14        System.out.println("Overflowed byte: " + smallByte);
15    }
16}

Next Lesson

Type Inference with var (Java 10+)

Continue learning with hands-on practice, examples, and exercises in the upcoming topic.

Related Lessons

Previous Lesson	Next Lesson
Primitive Data Types (byte, short, int, long, float, double, char, boolean)	Type Inference with var (Java 10+)

Practice Quiz

Test your understanding of this lesson with 1 questions. Each question has one correct answer.

Previous Next