Program to convert String to Double in java (example)

Converting strings to double values is a fundamental operation in Java programming, often essential for processing user inputs and numeric data manipulation. There are various methods to convert string to double values and each method has specific purpose.

Java offers a straightforward method, Double.parseDouble(), specifically designed to convert strings containing numeric representations into their double counterparts. Also, Java’s Double.valueOf() method and object instantiation mechanisms further extend the spectrum of conversion methodologies, offering versatility and control over the process.

Java’s Scanner class, renowned for its effectiveness in parsing various data types, including doubles, from input sources like strings, files, or user inputs.

Let’s explore these method to convert String to double.

1. Convert String to double  – Double.parseDouble

The Double.parseDouble() method is a straightforward way to convert a string to a double in Java. It takes a string argument representing a numeric value and returns the equivalent double value. It will throw a NumberFormatException if the string does not represent a valid double value or contains non-numeric characters.

public class StringToDoubleExample {
    public static void main(String[] args) {
        String salary = "15000.224";
        double salDouble = Double.parseDouble(salary);
        System.out.println("String value: " + salary);
        System.out.println("Double value: " + salDouble);
    }
}

Real time Example of Payroll System:

A payroll system requires converting string representations of salaries to double values for computation.

public class SalaryCalculator {
    public static void main(String[] args) {
        String salaryStr = "5000.50"; 
        double salary = Double.parseDouble(salaryStr);

        // Perform salary calculations or operations
        double bonus = 1000.0;
        double totalSalary = salary + bonus;

        System.out.println("Original Salary (String): " + salaryStr);
        System.out.println("Converted Salary (Double): " + salary);
        System.out.println("Total Salary with Bonus: " + totalSalary);
    }
}

2. Method – convert String to Double in java (example)

The Double.valueOf() method creates a Double object from a string and then extracts its double value. This approach allows for more flexibility with the Double object’s methods.
The returned Double object can be utilized in an object-oriented context, enabling functionalities such as interaction with collections, utilization of object-specific methods (e.g., compareTo(), equals(), toString()), and compatibility with object-based paradigms. Additionally, enables to use in collections like Hashmap as a Key or Value.

        String numStr = "42.0";
        Double doubleObj = Double.valueOf(numStr);
        double numDouble = doubleObj.doubleValue();
        System.out.println("String value: " + numStr);
        System.out.println("Double value: " + numDouble);

Real time Example – International Money Transfer:

A currency exchange application needs string-to-double conversion for handling different currency rates.

        public class CurrencyConverter {
    public static void main(String[] args) {
        String amountStr = "75.25"; 
        Double amountObj = Double.valueOf(amountStr);
        double foreignAmount = amountObj.doubleValue();

        // Perform currency conversion based on exchange rates
        double exchangeRate = 1.22; // Sample exchange rate
        double convertedAmount = foreignAmount * exchangeRate;

        System.out.println("Foreign Amount (String): " + amountStr);
        System.out.println("Converted Amount (Double): " + convertedAmount);
    }
}

3. Method – convert String to double in java (example)

Java’s Scanner class provides the facility to structured input, including numeric values, from strings. By utilizing the nextDouble() method of the Scanner class, we can extract double values from strings with various formatting or patterns.

The Scanner class tokenizes the input string based on specific delimiters, allowing extraction of double values or other data types according to defined patterns. Scanner class supports operations on input streams, enabling parsing of numeric values not only from strings but also from other sources such as files or user inputs via the console.

       String numStr = "99.9";
        Scanner scanner = new Scanner(numStr);
        double numDouble = scanner.nextDouble();
        System.out.println("String value: " + numStr);
        System.out.println("Double value: " + numDouble);

Real time Example – Temprature converter:

An application requires parsing user-entered temperature from a string to a double for processing.

import java.util.Scanner;

public class UserInputTemperature {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter temperature in Celsius: ");
        double userInputTemp = scanner.nextDouble();

        // Perform operations or calculations with user-entered temperature
        double convertedTemp = (userInputTemp * 9 / 5) + 32;

        System.out.println("Entered Temperature in Celsius: " + userInputTemp);
        System.out.println("Converted Temperature in Fahrenheit: " + convertedTemp);
    }
}

Summary: String to Double/double:

there are various methods to perform String to double/Double conversion and each solve particular purpose. We can use these methods to convert String to double/Double data types.