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
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
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.
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
Value- 145.34526 145.34526/3 = 48.44842
Java example to convert String to double using Double.valueOf
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
value- -245.67456
NumberFormatException
While converting string to double in Java NumberFormatException is thrown if an invalid number string is passed for conversion.
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
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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