Java Type Casting - Widening and Narrowing with Examples

⏱️ 8 min read • Beginner Level • Lesson 17

Type casting in Java means converting a value from one data type to another data type. It is commonly used when assigning values between different numeric types or when working with expressions.

Before learning type casting, you should understand Java variables, Java data types, and Java input and output.

What is Type Casting in Java?

Type casting is the process of converting one data type into another. For example, converting an int value into a double, or converting a double value into an int.

Types of Type Casting in Java

Java type casting is mainly divided into two types:

Java Type Conversion Hierarchy

Widening Type Casting in Java

Widening casting happens when a smaller data type is converted into a larger data type. Java performs widening casting automatically because there is no risk of data loss.

public class WideningCastingExample {
    public static void main(String[] args) {
        int number = 100;
        double result = number; // automatic casting: int to double

        System.out.println("Integer value: " + number);
        System.out.println("Double value: " + result);
    }
}

Output:

Integer value: 100
Double value: 100.0

Narrowing Type Casting in Java

Narrowing casting happens when a larger data type is converted into a smaller data type. Java does not perform narrowing automatically because it may cause data loss. Therefore, narrowing casting must be done manually using parentheses.

smallerType variable = (smallerType) largerValue;

public class NarrowingCastingExample {
    public static void main(String[] args) {
        float price = 99.75f;
        int amount = (int) price; // manual casting: float to int
        System.out.println("Flaot price: " + amount);
        System.out.println("Integer amount: " + amount);

        double value = 99.99;
        int number = (int) value; // manual casting: double to int

        System.out.println("Double value: " + value);
        System.out.println("Integer value: " + number);
    }
}

Output:

Float price: 99.75
Integer amount: 99.75
Double value: 99.99
Integer value: 99

Real-World Use of Type Casting

Type casting is commonly used when working with calculations, user input, APIs, databases, and file processing.

Java Type Conversion Order

Java follows a natural order for widening numeric conversions. Smaller types can be automatically converted to larger types.

Type Casting in Expressions

When different numeric types are used in an expression, Java may automatically promote smaller types to larger types before calculation.

public class ExpressionCastingExample {
    public static void main(String[] args) {
        int a = 10;
        double b = 5.5;

        double result = a + b; // int is promoted to double

        System.out.println(result);
    }
}

Output:

15.5

char and int Casting in Java

In Java, char values are internally stored as Unicode numbers. Because of this, a char can be converted to an int to get its Unicode value.

public class CharCastingExample {
    public static void main(String[] args) {
        char ch = 'A';
        int unicodeValue = ch;

        System.out.println("Character: " + ch);
        System.out.println("Unicode value: " + unicodeValue);
    }
}

Output:

Character: A
Unicode value: 65

You can also cast an integer value back to a character.

public class IntToCharCasting {
    public static void main(String[] args) {
        int number = 66;
        char ch = (char) number;

        System.out.println(ch);
    }
}

Output:

B

byte, short and int Casting

In Java expressions, byte and short values are promoted to int before calculation. This is a common interview question.

public class ByteShortPromotion {
    public static void main(String[] args) {
        byte a = 10;
        byte b = 20;

        // byte c = a + b; // Error: result is promoted to int

        int result = a + b;
        byte c = (byte) (a + b);

        System.out.println(result);
        System.out.println(c);
    }
}

Output:

30
30

Loss of Data in Narrowing Casting

Narrowing casting can cause data loss because a larger data type may contain a value that cannot fit into a smaller data type.

public class DataLossExample {
    public static void main(String[] args) {
        int number = 130;
        byte value = (byte) number;

        System.out.println(value);
    }
}

Output:

-126

Common Mistakes in Java Type Casting

public class CommonCastingMistake {
    public static void main(String[] args) {
        double price = 99.99;

        // int amount = price; // Error: possible lossy conversion

        int amount = (int) price; // Correct explicit casting

        System.out.println(amount);
    }
}

Output:

99

Java Type Casting Summary Table

Interview Questions ⭐

🧠 Test your understanding with a quick quiz

int x = 130;
byte y = (byte) x;
System.out.println(y);

byte a = 10;
byte b = 20;
byte c = a + b;

int num = 100;
double result = num;
System.out.println(result);

double price = 99.99;
int amount = (int) price;

int a = 10;
double b = a;

double value = 45.89;
int number = (int) value;
System.out.println(number);

char ch = 'A';
int value = ch;
System.out.println(value);

🎉 Great job! Continue learning Java step by step.