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How to Convert Double to String in Java? Programs

Data conversion is a common and essential task in Java programming. Whether you're building a financial application, scientific software, or even a simple calculator, there will come a time when you need to convert double to String in Java. This is crucial for displaying numeric data, storing it in files, or passing it as part of a message in a Java application.

This tutorial will walk you through the various methods and techniques available to convert a double to a String in Java effectively. 

We'll explore the built-in Java methods, such as String.valueOf(), Double.toString(), and String.format(), and discuss when and how to use each one. 

Concepts to Learn:

Double to String in Java Using String.valueOf()

Here's a Java program to convert a double to a String using the String.valueOf(double) method:

Code

public class DoubleToStringExample {
    public static void main(String[] args) {
        // Define a double value
        double doubleValue = 123.456;

        // Convert the double to a string using String.valueOf()
        String stringValue = String.valueOf(doubleValue);

        // Display the original double and the converted string
        System.out.println("Original double value: " + doubleValue);
        System.out.println("Converted string value: " + stringValue);
    }
}

Output

Original double value: 123.456
Converted string value: 123.456

Explanation

  • We start by defining a double variable named doubleValue with a value of 123.456.

  • Next, we use the String.valueOf(double) method to convert the double value to a String. This method takes a double as input and returns a String representation of that double.

  • We store the converted String in a variable called stringValue.

  • Finally, we print out both the original double value and the converted String value using System.out.println() statements.

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Java Double to String Using Double.toString()

Here's a program to convert double to String in Java programming using the Double.toString(double) method:

Code

public class DoubleToStringExample {
    public static void main(String[] args) {
        // Define a double value
        double doubleValue = 789.123;

        // Convert the double to a string using Double.toString()
        String stringValue = Double.toString(doubleValue);

        // Display the original double and the converted string
        System.out.println("Original double value: " + doubleValue);
        System.out.println("Converted string value: " + stringValue);
    }
}

Output

Original double value: 789.123
Converted string value: 789.123

Explanation

  • We start by defining a double variable named doubleValue with a value of 789.123.

  • Next, we use the Double.toString(double) method to convert the double value to a String. This method is a static method of the Double class and takes a double as input, returning a String representation of the double.

  • We store the converted String in a variable called stringValue.

  • Finally, we print out both the original double value and the converted String value using System.out.println() statements.

Convert Doube to String in Java Using String.format()

Here's a program on how to convert double to String in Java using the String.format() method:

Code

public class DoubleToStringExample {
    public static void main(String[] args) {
        // Define a double value
        double doubleValue = 123.456;

        // Convert the double to a string using String.format()
        String stringValue = String.format("%.2f", doubleValue);

        // Display the original double and the converted string
        System.out.println("Original double value: " + doubleValue);
        System.out.println("Converted string value: " + stringValue);
    }
}

Output

Original double value: 123.456
Converted string value: 123.46

Explanation

  • We start by defining a double variable named doubleValue with a value of 123.456.

  • Next, we use the String.format() method to convert the double value to a formatted String. In this example, we specify "%.2f" as the format string. %.2f is a format specifier that formats the double with two decimal places.

  • We store the formatted String in a variable called stringValue.

  • Finally, we print out both the original double value and the converted formatted String value using System.out.println() statements.

Convert Double to String in Java Using DecimalFormat class

To convert a double to a String using the DecimalFormat class in Java, you can follow this example. The DecimalFormat class provides more advanced formatting options than some other methods:

Code

import java.text.DecimalFormat;

public class DoubleToStringExample {
    public static void main(String[] args) {
        // Define a double value
        double doubleValue = 789.123;

        // Create a DecimalFormat instance with the desired format
        DecimalFormat decimalFormat = new DecimalFormat("#0.00");

        // Convert the double to a string using DecimalFormat
        String stringValue = decimalFormat.format(doubleValue);

        // Display the original double and the converted string
        System.out.println("Original double value: " + doubleValue);
        System.out.println("Converted string value: " + stringValue);
    }
}

Output

Original double value: 789.123
Converted string value: 789.12

Explanation

  • We start by defining a double variable named doubleValue with a value of 789.123.

  • We create an instance of the DecimalFormat class, named decimalFormat, with the desired format. In this case, "#0.00" is used as the format pattern. This format pattern specifies that we want two decimal places.

  • We use the decimalFormat.format(doubleValue) method to convert the double value to a formatted String. The format method formats the double value according to the pattern specified when creating the DecimalFormat instance.

  • We store the formatted String in a variable called stringValue.

  • Finally, we print out both the original double value and the converted formatted String value using System.out.println() statements.

Java Double to String Using StringBuilder or StringBuffer

To convert a double to a String using the StringBuilder or StringBuffer concatenation method in Java, you can follow this example. This method involves creating a StringBuilder or StringBuffer and appending the double value as a string:

Code

public class DoubleToStringExample {
    public static void main(String[] args) {
        // Define a double value
        double doubleValue = 123.456;

        // Create a StringBuilder instance
        StringBuilder stringBuilder = new StringBuilder();

        // Append the double value as a string
        stringBuilder.append(doubleValue);

        // Convert the StringBuilder to a string
        String stringValue = stringBuilder.toString();

        // Display the original double and the converted string
        System.out.println("Original double value: " + doubleValue);
        System.out.println("Converted string value: " + stringValue);
    }
}

Output

Original double value: 123.456
Converted string value: 123.456

Explanation

  • We start by defining a double variable named doubleValue with a value of 123.456.

  • We create a StringBuilder instance named stringBuilder. Alternatively, you can use StringBuffer if you require thread safety.

  • We use the append() method of the stringBuilder to add the double value as a string to the StringBuilder.

  • We convert the StringBuilder to a String by calling the toString() method, storing the result in a variable called stringValue.

  • Finally, we print out both the original double value and the converted String value using System.out.println() statements.

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