Typecasting refers to the process of converting one data type into another. Since Java is a statically-typed language, the type of each variable is defined at the time of declaration. There are two main types of typecasting in Java:
- Implicit Typecasting (Widening Casting)
- Explicit Typecasting (Narrowing Casting)
Implicit Typecasting
Implicit typecasting occurs automatically when a smaller data type is converted into a larger one. This happens when there is no risk of losing information or precision. For example, converting from an int to a long or from a float to a double works without issues, as the larger data type can comfortably hold the value of the smaller type.
Syntax
Java automatically performs widening typecasting when necessary.
Example
Output
In this example, the int variable num1 is automatically converted into a long type and assigned to num2 without needing any explicit casting.
Explicit Typecasting
Explicit typecasting is when you manually convert a larger data type to a smaller one. This can sometimes result in a loss of data because the smaller data type may not be able to hold the full value of the larger type. For instance, converting a double to an int will discard the decimal part.
In these cases, you must use a cast operator to explicitly perform the conversion.
Syntax
Example
Output
In this example, the double value 45.67 is explicitly cast to an int, and the decimal part is lost.
Differences between Implicit and Explicit Typecasting
| Feature | Implicit Typecasting (Widening) | Explicit Typecasting (Narrowing) |
|---|---|---|
| Definition | Automatically performed by the compiler when converting a smaller type to a larger type. | Manually performed by the programmer when converting a larger type to a smaller type. |
| Process | Happens automatically without any explicit instruction. | Requires the programmer to use a cast operator (type). |
| Data Loss | No data loss, as the smaller type fits within the larger one. | Data loss may occur because the smaller type cannot fully represent the larger value. |
| Example Conversion | int to long, float to double. | double to int, long to short. |
| Example Code | long num2 = num1; (where num1 is an int). |
int num2 = (int) num1; (where num1 is a double). |
| Compiler Involvement | The compiler automatically handles the conversion. | The programmer must manually specify the cast. |
| Syntax | No cast syntax required. | Uses cast syntax: (type) variable. |
| Type Compatibility | Safe conversion, as the larger type can hold the smaller type. | Potential for data loss if the larger type has a value outside the range of the smaller type. |
| Example (No Data Loss) | int num = 100; double result = num; |
double num = 45.67; int result = (int) num; (decimal part lost) |
