Java - Convert String to double

To convert a String to double in Java, we can use:

Double.parseDouble()

static double parseDouble(String s): Returns a new double initialized to the value represented by the specified String, as performed by the valueOf method of class Double.

double d1 = Double.parseDouble("99.90");
System.out.println(d1);  // 99.9

double d2 = Double.parseDouble("99.901");
System.out.println(d2);  // 99.901

double d3 = Double.parseDouble("99.9010D");
System.out.println(d3);  // 99.901

double d4 = Double.parseDouble("-99.909d");
System.out.println(d4);  // -99.909

Double.valueOf()

static Double valueOf(double d): Returns a Double instance representing the specified double value.

double d1 = Double.valueOf("88.80");
System.out.println(d1);  // 88.9

double d2 = Double.valueOf("88.801");
System.out.println(d2);  // 88.801

double d3 = Double.valueOf("88.8010d");
System.out.println(d3);  // 88.801

double d4 = Double.valueOf("-88.808D");
System.out.println(d4);  // -88.808

Implicit casting automatically unbox Double into double.

Deprecated: Double‘s Constructor

Double(String s) is deprecated.

It is rarely appropriate to use this constructor. Use parseDouble(String) to convert a string to a double primitive, or use valueOf(String) to convert a string to a Double object.

double d1 = new Double("123");
System.out.println(d1);  // 123

double d2 = new Double("-88.808D");
System.out.println(d2);  // -88.808D

double d3 = new Double("FF00"); // NumberFormatException
System.out.println(d3);

DecimalFormat.parse()

parse(String source) throws ParseException: Parses text from the beginning of the given string to produce a number. The method may not use the entire text of the given string.

import java.text.DecimalFormat;
import java.text.ParseException;

DecimalFormat decimalFormat = new DecimalFormat();
try {
    double l = decimalFormat.parse("456.0990D").doubleValue();
    System.out.println(l);  // 456.99
} catch (ParseException e) {
    System.out.println(e.getMessage());
}

We also can use external libraries like Apache Commons NumberUtils, Spring's NumberUtils, and Google's Guava primitive Doubles.

Apache Commons NumberUtils

static double toDouble(String str): Convert a String to a double, returning 0.0d if the conversion fails.
static double toDouble(String str, double defaultValue): Convert a String to a double, returning a default value if the conversion fails.
static Double createDouble(String str): Convert a String to a Double.

import org.springframework.util.NumberUtils;

double d1 = NumberUtils.toDouble("365.536");
System.out.println(d1);  // 365.536

double d2 = NumberUtils.toDouble("");
System.out.println(d2);  // 0.0

double d3 = NumberUtils.toDouble("365.5360D", 0);
System.out.println(d3);  // 365.536

double d4 = NumberUtils.toDouble("xyz", -1);
System.out.println(d4);  // -1.0

double d5 = NumberUtils.toDouble("", -1);
System.out.println(d5);  // -1.0

double d6 = NumberUtils.createDouble("365.5360d");
System.out.println(d6);  // 365.536

double d7 = NumberUtils.createDouble("-#88FF");  // NumberFormatException
System.out.println(d7);

Spring NumberUtils

Similar like in Converting String to int and Converting String to long, we can use Spring's NumberUtils to parse String to number (in this case double).

import org.springframework.util.NumberUtils;

double d1 = NumberUtils.parseNumber("95.085", Double.class);
System.out.println(d1);  // 95.085

double d2 = NumberUtils.parseNumber("-31.490", Double.class);
System.out.println(d2);  // -31.49

Google Guava Doubles.tryParse()

static Double tryParse(String string): Parses the specified string as a double-precision floating point value.

import com.google.common.primitives.Longs;

double d1 = Doubles.tryParse("512.345");
System.out.println(d1);  // 512.345

double d2 = Doubles.tryParse("-512.3450D");
System.out.println(d2);  // -512.345

Also check on How to Handle NumberFormatException in Java

This article is part of Java String With Examples Series.

How to Handle NumberFormatException in Java

Desson Ariawan