1. Introduction

In Java, we often need to convert a String to a Double, which can be achieved using the Double.parseDouble() method or by creating a new instance of the Double class. This conversion is especially useful when dealing with user input or reading from a file where numeric values are represented as strings.

2. Program Steps

1. Define a main method inside a Java class.

2. Declare a String variable with a numeric value.

3. Use the Double.parseDouble() method to convert the String to a Double.

4. Alternatively, create a new instance of the Double class for conversion.

5. Print the original String and the converted Double values.

3. Code Program

public class StringToDouble {

    public static void main(String[] args) {
        // Step 2: Declare a String variable with a numeric value
        String numericString = "123.45";

        // Step 3: Use the Double.parseDouble() method to convert the String to a Double
        double parsedDouble = Double.parseDouble(numericString);

        // Step 4: Alternatively, create a new instance of the Double class for conversion
        Double objectDouble = new Double(numericString);

        // Step 5: Print the original String and the converted Double values
        System.out.println("Original String: " + numericString);
        System.out.println("Parsed Double: " + parsedDouble);
        System.out.println("Object Double: " + objectDouble);
    }
}

Output:

Original String: 123.45
Parsed Double: 123.45
Object Double: 123.45

4. Step By Step Explanation

– Step 1: A main method is defined inside the StringToDouble class.

– Step 2: A String variable numericString is declared with a numeric value represented as a String.

– Step 3: The Double.parseDouble() method is used to convert numericString to a primitive double data type, and the result is stored in the variable parsedDouble.

– Step 4: An alternative approach is used by creating a new instance of the Double class. The result is stored in the objectDouble variable which is of type Double.

– Step 5: The original String value numericString and the converted Double values parsedDouble and objectDouble are printed to the console.

This program demonstrates two ways to convert a String to a Double in Java, using Double.parseDouble() for primitive double and creating a new Double object for the wrapper class.