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Type Casting

Type Casting

Let's learn how a variable of one type can be casted to a variable of another type.

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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).

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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 for the next line, where we divide var1 by var2.

Explicit type casting

We also have operations that explicitly change the type of variables. To convert an int type variable to a double type, we have the (double) operation. Similarly, to convert a double type variable to an int type, just add (int) before it and assign it to an int type variable. During the integer casting with the (int) method, the decimal part of the double type variable is dropped. The higher data types, e.g. double, (having larger size) are converted into lower data types, e.g. int, (having smaller size).

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class ExplicitTypeCasting 
{
    public static void main(String args[]) 
    {
        // casting int to double
        int intVar = 3; // int type variable
        System.out.println(intVar); // prints 3
        double castedDoubleVar = (double) intVar; // casting int to a double variable
        System.out.println(castedDoubleVar); // prints 3.0
        // casting double to int
        double doubleVar = 3.14;    // double type variable
        System.out.println(doubleVar);  // prints 3.14
        
        int castedIntVar = (int) doubleVar; // casting double to an int variable, decimal dropped
        System.out.println(castedIntVar);   // prints 3
    }
}

At line 6, we create an int variable: intVar. Then, at line 9, we explicitly type cast the variable to a double type variable: castedDoubleVar. We use the (double) method for this.

Similarly, at line 13, we create a double variable: doubleVar. Then, at line 16, we explicitly type cast the variable ...