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How to Convert Int to Double in Java? (Integer to Double)

In Java programming, it's common to encounter situations where you need to work with different data types. One such common task is to convert an integer (int) into a double (double). While Java is a strongly-typed language that typically requires explicit type conversions, the process of converting from int to double is straightforward once you understand the fundamentals.

In this tutorial, we'll walk you through the step-by-step process to convert int to double in Java. We'll explore various methods and techniques, ensuring you have a solid grasp of how to perform this conversion effectively. 

Concepts to Learn for This Program:

Convert Integer to Double in Java Using Assignment Operator

Here's the Java program to convert int to double using the assignment operator, along with the explanation and expected output:

Code

public class IntToDoubleConversion {
    public static void main(String[] args) {
        int intValue = 42;
        double doubleValue = intValue; // Using assignment operator to convert int to double

        System.out.println("Original int value: " + intValue);
        System.out.println("Converted double value: " + doubleValue);
    }
}

Output

Original int value: 42
Converted double value: 42.0

Explanation

  • We declare an int variable intValue and initialize it with the value 42.

  • We declare a double variable doubleValue and assign the intValue to it. In Java, this is an example of implicit type casting or widening conversion, where the int value is automatically converted to a double because a double can hold a wider range of values than an int.

  • We use System.out.println to display the original int value and the converted double value.

As you can see, the original int value 42 is converted to a double with the value 42.0. Java performs this conversion automatically because a double can represent decimal values, while an int can only represent whole numbers.

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Java Int to Double Using Double(int)

You can convert an int to a double in Java using a wrapper class constructor, specifically Double(int).

Code

public class IntToDoubleConversion {
    public static void main(String[] args) {
        int intValue = 42;
        Double doubleValue = new Double(intValue); // Using wrapper class constructor

        System.out.println("Original int value: " + intValue);
        System.out.println("Converted double value: " + doubleValue);
    }
}

Output

Original int value: 42
Converted double value: 42.0

Explanation

  • We declare an int variable intValue and initialize it with the value 42.

  • We create a Double object doubleValue by using the Double(int) constructor. This constructor takes an int as an argument and converts it to its double representation.

  • We use System.out.println to display the original int value and the converted double value.

Convert Int to Double in Java Using Double.valueOf()

You can also convert an int to a double in Java using the Double.valueOf(intValue) method.

Code

public class IntToDoubleConversion {
    public static void main(String[] args) {
        int intValue = 42;
        double doubleValue = Double.valueOf(intValue); // Using Double.valueOf(intValue)

        System.out.println("Original int value: " + intValue);
        System.out.println("Converted double value: " + doubleValue);
    }
}

Output

Original int value: 42
Converted double value: 42.0

Explanation

  • We declare an int variable intValue and initialize it with the value 42.

  • We use the Double.valueOf(intValue) method to convert the int value to its double representation. This method takes an int as an argument and returns a Double object representing the equivalent double value.

  • We assign the result to the doubleValue variable, which now holds the converted double value.

  • We use System.out.println to display the original int value and the converted double value.

 

Int to Double Conversion in Java Using Typecasting

In this method, we will convert an integer to double in Java using type casting. 

Code

public class IntToDoubleConversion {
    public static void main(String[] args) {
        int intValue = 42;
        double doubleValue = (double) intValue; // Using type casting

        System.out.println("Original int value: " + intValue);
        System.out.println("Converted double value: " + doubleValue);
    }
}

Output

Original int value: 42
Converted double value: 42.0

Explanation

  • We declare an int variable intValue and initialize it with the value 42.

  • We use Java type casting to convert the int value to a double. The (double) before intValue explicitly tells Java to treat intValue as a double during the conversion.

  • We assign the result to the doubleValue variable, which now holds the converted double value.

  • We use System.out.println to display the original int value and the converted double value.

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