Java Casting

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Index

1. Type Casting
2. Explicit conversion
3. Implicit Type Casting
4. Explicit Type Casting
5. Examples

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Type Casting

The process of converting the value of one data type (int, float, double, etc.) to another data type is known as typecasting.

In Java, there are 13 types of type conversion. However, in this tutorial, we will only focus on the major 2 types.

1. Explicit conversion
2. Implicit Type Casting
3. Explicit Type Casting

To learn about other types of type conversion, visit Java Type Conversion (official Java documentation).

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Explicit conversion

Using a method that takes an argument of one type and returns a value of another type

Some of this methods are:

• Integer.parseInt()
• Double.parseDouble()
• Integer.toString()
• Math.round()
• Math.floor()
• Math.ceil()

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Implicit Type Casting

Java automatically converts one data type to another data type.

Converting int to double

 
// create int type variable
int num = 10;
    System.out.println("The integer value: " + num);
 
// convert into double type
double data = num;
System.out.println("The double value: " + data);
 
// Output:
// The integer value: 10
// The double value: 10.0

Here, the Java first converts the int type data into the double type. And then assign it to the double variable.

Tip

In the case of Implicit Type Casting, the lower data type (having smaller size) is converted into the higher data type (having larger size). Hence there is no loss in data. This is why this type of conversion happens automatically.

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Explicit Type Casting

In Explicit Type Casting, we manually convert one data type into another using the parenthesis.

Example: Converting double into an int

// create double type variable
double num = 10.99;
System.out.println("The double value: " + num);
 
// convert into int type
int data = (int)num;
System.out.println("The integer value: " + data);
 
// Output:
// The double value: 10.99
// The integer value: 10

In the above example, we are assigning the double type variable named num to an int type variable named data.

Notice the line,

int data = (int)num;

Here, the int keyword inside the parenthesis indicates that that the num variable is converted into the int type.

In the case of Narrowing Type Casting, the higher data types (having larger size) are converted into lower data types (having smaller size). Hence there is the loss of data. This is why this type of conversion does not happen automatically.

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Examples

Expressions	Type	Value
(int)2.71828	int	2
Math.round(2.71828)	long	2
(int)Math.round(2.71828)	int	2
(int)Math.round(3.14159)	int	3
Integer.parseInt("42")	int	42
"42" + 99	String	“4299”
42 * 0.4	double	16.8
(int)42 * 0.4	double	16.8
42 * (int)0.4	int	0
(int)(42 * 0.4)	int	16

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