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How to check that a string is parse-able to a double in java?
Using the parseDouble() method
The parseDouble() method of the java.lang.Double class accepts a String value, parses it, and returns the double value of the given String.
If you pass a null value to this method, it throws a NullPointerException and if this method is not able to parse the given string into a double value you, it throws a NumberFormatException.
Therefore, to know whether a particular string is parse-able to double or not, pass it to the parseDouble method and wrap this line with try-catch block. If an exception occurs this indicates that the given String is not pars able to double.
Example
import java.util.Scanner;
public class ParsableToDouble {
public static void main(String args[]) {
try {
Scanner sc = new Scanner(System.in);
System.out.println("Enter a string value: ");
String str = sc.next();
Double doub = Double.parseDouble(str);
System.out.println("Value of the variable: "+doub);
}catch (NumberFormatException ex) {
System.out.println("Given String is not parsable to double");
}
}
}Output
Enter a string value: 2245g Given String is not parsable to double
Using the valueOf() method
Similarly, the valueOf() method of the Double class (also) accepts a String value as a parameter, trims the excess spaces and returns the double value represented by the string. If the value given is not parsable to double this method throws a NumberFormatException.
Example
import java.util.Scanner;
public class ParsableToDouble {
public static void main(String args[]) {
try {
Scanner sc = new Scanner(System.in);
System.out.println("Enter a string value: ");
String str = sc.next();
Double doub = Double.valueOf(str);
System.out.println("Value of the variable: "+doub);
}catch (NumberFormatException ex) {
System.out.println("Given String is not parsable to double");
}
}
}Output
Enter a string value: 2245g Given String is not parsable to double
Using the constructor of the Double class
One of the constructor of the Double class accepts a String as a parameter and constructs an (Double) object that wraps the given value. If the string passed to this constructor is not parsable to Double a NumberFormatException will be thrown.
Example
import java.util.Scanner;
public class ParsableToDouble {
public static void main(String args[]) {
try {
Scanner sc = new Scanner(System.in);
System.out.println("Enter a string value: ");
String str = sc.next();
Double doub = new Double(str);
System.out.println("Value of the variable: "+doub);
}catch (NumberFormatException ex) {
System.out.println("Given String is not parsable to double");
}
}
}Output
Enter a string value: 2245g Given String is not parsable to double
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