Java Type Conversion

In this tutorial, we will learn Java Type Conversionand their types.

While learningBefore Java type conversion, make sure you understandJava Data Types.

Type Conversion

The process of converting a value of one data type (int, float, double, etc.) to another data type is called type conversion.

In Java, there are13of type conversion. However, in this tutorial, we will only focus on the main two types.

1, Type conversion

2, Automatic type conversion

Automatic type conversion

In, Narrowing conversionIn automatic type conversion

, Java automatically converts one data type to another.

class Main {
　　public static void main(String[] args) {
　　　　//Create an int type variable
　　　　int num =　10;
　　　　Example: Convert int to double　+　num);
　　　　//Converted to double type
　　　　double data = num;
　　　　System.out.println("Double value: ",　+　data);
　　}
}

Output Result

Integer value:　10
Double value:　10.0

In the above example, we assign the int type variable named num to the double type variable named data.

Here, Java first converts the int type data to double type. Then it assigns it to the double variable.

InAutomatic type conversionIn the case, a lower data type (with a smaller size) will be converted to a higher data type (with a larger size). Therefore, there is no data loss. This is why this type of conversion happens automatically.

Note: This is also calledImplicit type conversion.

Type casting

InType castingIn, we use parentheses to manually convert one data type to another.

Example: Convert double to int

class Main {
　　public static void main(String[] args) {
　　　　//Create a double type variable
　　　　double num =　10.99;
　　　　System.out.println("Double value: ",　+　num);
　　　　//Converted to int type
　　　　int data = (int)num;
　　　　System.out.println("Integer value: ",　+　data);
　　}
}

Output Result

Double value:　10.99
Integer value:　10

In the above example, we assign the double variable named num to the int variable named data.

Note this line,

int data = (int)num;

Here, the int keyword in the parentheses indicates that the num variable is converted to the int type.

InType castingIn the case, a higher data type (with a larger size) will be converted to a lower data type (with a smaller size). Therefore, there is data loss. This is why this type of conversion does not happen automatically.

Note: This is also calledExplicit type conversion.

Let's look at some other type conversion examples in Java.

Example1Type conversion from int to String

class Main {
　　public static void main(String[] args) {
　　　　//　Create an int type variable
　　　　int num =　10;
　　　　System.out.println("Integer value is: ");　+　num);
　　　　//Convert int to string type
　　　　String data = String.valueOf(num);
　　　　System.out.println("String value is: ");　+　data);
　　}
}

Output Result

Integer value is:　10
String value is:　10

In the above program, note this line

String data = String.valueOf(num);

Here, we useJava String classThe valueOf() method converts an int type variable to a string.

Example2: Type conversion from string (String) to integer (int)

class Main {
　　public static void main(String[] args) {
　　　　//Create a string type variable
　　　　String data = "10";
　　　　System.out.println("String value is: ");　+　data);
　　　　//Convert string variable to int
　　　　int num = Integer.parseInt(data);
　　　　System.out.println("Integer value is: ");　+　num);
　　}
}

Output Result

String value is:　10
Integer value is:　10

In the above example, please note the following line

int num = Integer.parseInt(data);

In this example, we used the parseInt() method of the Java Integer class to convert a string type variable to an int variable.

NoteIf a string variable cannot be converted to an integer variable, a NumberFormatException will be thrown.