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Ace the AP Computer Science Exam for High Schoolers

Type Casting

Explore the concept of type casting in Java, focusing on converting between int and double primitive types. Understand implicit casting during operations, explicit casting using syntax, and how overflow affects value ranges. This lesson helps you develop practical skills for handling type conversions correctly in your code.

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While writing programs in Java, you will often need to change an int type variable to a double type variable or vice versa. There are also some operations that implicitly interconvert types. For example, the division of an int type variable with a double type variable. Let’s look at this case first.

Implicit type casting

In the basic cases, i.e., the division of similar type variables, the data type of the result remains preserved. This means that:

  • The division of two int type variables results in another int type variable with the decimal dropped: 7/2 = 3
  • The division of two double type variables results in another double type variable: 7.0/2.0 = 3.5

However, if the variables have different types, i.e., one variable is int type and the other is double type, the resulting variable is of double type, and the decimal part is retained. The lower data type int (having smaller size) is converted into the higher data type double (having larger size).

Java
class ImplicitTypeCasting 
{
    public static void main(String args[]) 
    {
        double var1 = 2;  // double type variable
        int var2 = 7;     // int type variable
        System.out.println(var2/var1);  // int type divided by double type
        System.out.println(var1/var2);  // double type divided by int type
    }
}

We declare a double type variable (var1) and an int type variable (var2). At line 8, we divide var2 by var1. Notice that we get a double value as a result instead of an int value. The same goes ...