Type Conversion and Casting

Java From Beginner To Advanced

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In Java, type conversion and casting allow us to convert a value of one data type into another. This is useful when you need to work with different types of data in your program.

There are two types of type casting in Java:

implicit (widening)
explicit (narrowing)

What Is Type Casting?

Type casting is the process of converting a value from one data type to another. In Java, this can be done in two ways:

Implicit Type Casting (Widening): Automatically done by the Java compiler when converting a smaller data type to a larger data type.
Explicit Type Casting (Narrowing): Requires manual intervention to convert a larger data type to a smaller data type.

Implicit Type Casting (Widening)

Implicit type casting happens automatically when a smaller data type is assigned to a larger data type. This is safe because no data is lost.

From: byte → short → int → long → float → double

Syntax

largerType variableName = smallerTypeValue;

Example: Implicit Type Casting

Below is an example of widening conversion. Here, the int value myInt is automatically converted to a double value myDouble.

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Explicit Type Casting (Narrowing)

Explicit type casting is required when a larger data type is converted to a smaller data type. This can result in data loss and requires manual intervention using the casting operator (type).

From: double → float → long → int → short → byte

Syntax

smallerType variableName = (smallerType) largerTypeValue;

Example 1: Narrowing from double to int

Here, the double value myDouble is explicitly cast to an int. The fractional part (.99) is lost during this conversion.

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Example 2: Narrowing from int to byte

In this example, the int value 130 is explicitly cast to a byte. Since the byte range is only -128 to 127, the value wraps around to -126.

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Combining Implicit and Explicit Casting

Sometimes, you may need to combine implicit and explicit casting in a single program.

Example: Mixing Implicit and Explicit Casting

In the example below, the int value is implicitly converted to double, and then the double value is explicitly cast to float.

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Implicit vs. Explicit Casting

Feature	Implicit Casting (Widening)	Explicit Casting (Narrowing)
Process	Automatic	Manual
Safety	Safe, no data loss	May result in data loss or value wrapping
Example Conversion	`int → double`	`double → int`
Syntax	`largerType variable = smallerValue;`	`smallerType variable = (smallerType) largerValue;`

Type casting is an essential concept in Java that allows you to handle data flexibly. However, you should be cautious with explicit casting as it may lead to unexpected behavior or data loss. Practice these examples to understand how and when to use type casting effectively.

In the next lesson, we will explore Java Basic Input and Output, where we’ll learn to read and display data in Java programs.

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