To convert String to double in Java you can use one of the following options-
- Double.parseDouble(String s)– Returns a new double initialized to the value represented by the specified String. Throws NumberFormatException if the string does not contain a parsable double.
- Double.valueOf(String s)– Returns a Double object holding the double value represented by the argument string s. Throws NumberFormatException if the string does not contain a parsable number.
As you can see parseDouble() method returns a double primitive where as valueOf() method returns a Double object.
Java example to convert String to double using Double.parseDouble
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public class StringToDouble { public static void main(String[] args) { String num = "145.34526"; try{ double d = Double.parseDouble(num); System.out.println("Value- " + d); // can be used in arithmetic operations now System.out.println(d+"/3 = " + d/3); }catch(NumberFormatException ex){ System.out.println("Error while conversion " + ex.getMessage()); } } } |
Output
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Value- 145.34526 145.34526/3 = 48.44842 |
For double numbers you can use “d” or “D” (even f or F which denotes double) so a String like this – “145.34d” won’t result in NumberFormatException while converting. But having any other alphabet like “145.34c” will throw exception.
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public class StringToDouble { public static void main(String[] args) { String num = "145.34526d"; try{ double d = Double.parseDouble(num); System.out.println("Value- " + d); // can be used in arithmetic operations now System.out.println(d+"/3 = " + d/3); }catch(NumberFormatException ex){ System.out.println("Error while conversion " + ex.getMessage()); } } } |
Output
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Value- 145.34526 145.34526/3 = 48.44842 |
Java example to convert String to double using Double.valueOf
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public class StringToDouble { public static void main(String[] args) { String str = "-245.67456"; try{ Double d = Double.valueOf(str); System.out.println("value- " + d); }catch(NumberFormatException exp){ System.out.println("Error in conversion " + exp.getMessage()); throw exp; } } } |
Output
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value- -245.67456 |
NumberFormatException
While converting string to double in Java NumberFormatException is thrown if an invalid number string is passed for conversion.
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public class StringToDouble { public static void main(String[] args) { String str = "45.674c"; try{ Double d = Double.valueOf(str); System.out.println("value- " + d); }catch(NumberFormatException exp){ System.out.println("Error in conversion " + exp.getMessage()); throw exp; } } } |
Output
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Error in conversion For input string: "45.674c"Exception in thread "main" java.lang.NumberFormatException: For input string: "45.674c" at java.base/jdk.internal.math.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:2054) at java.base/jdk.internal.math.FloatingDecimal.parseDouble(FloatingDecimal.java:110) at java.base/java.lang.Double.parseDouble(Double.java:543) at java.base/java.lang.Double.valueOf(Double.java:506) at com.knpcode.programs.StringToDouble.main(StringToDouble.java:8) |
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