NumberFormatException in Java

Introduction to NumberFormatException in Java

It is thrown while converting a string of improper format to a numeric value like an integer or float. An example of improper format can be a string that has a boolean value. If this string is converted to a numeric value, then an exception is thrown. For instance, parsing a string that is null to an integer. It is an unchecked exception, also known as a run time exception. The try-catch block is used for handling this exception. When operating with the string, a parseInt() method is used for converting a string to an integer type. parseInt() method can be used in two ways as given below:

Both methods are used for converting a string to an integer. The only difference between these two syntaxes is the parameter radix. When radix=10, the first method is considered equivalent to that of the second method.

Constructors of NumberFormatException

Hiring Partners:

GoogleAmazonMicrosoftFlipkartAdobe1200+ more

What Causes NumberFormatException?

There are various problems related to formatting string which is improper. Here are a few important reasons for NumberFormatException:

• Null input string: Integer.parseInt("null");
• Input string which is empty: Float.parseFloat(“”);
• Leading or trailing white spaces in input string: Integer abc=new Integer(“ 123 “);
• Extra symbol in input string: Float.parseFloat(4,123);
• Input string with data which is non-numeric: Double.parseDouble(“FifityFive”);
• Alphanumeric input string: Integer.valueOf(“33.three”);
• Input string with exceeded range of datatype: Integer.parseInt(“1826589745243”);
• Type mismatch between the value of input string and its method: Integer.parseInt("12.33");

Example of NumberFormatException

Program to illustrate NumberFormatException in java. In this example, we will try to understand how and why NumberFormartException occurs.

Output:

Explanation: As per code, as soon as the user enters a number other than Integer like double or float then the NumberFormatException occurs.

Flow of the given code:

• Input is taken from user
• The input is parsed using parseInt
• If there is an error while parsing
• NumberFormatException is thrown
• Else Output is printed

How to Handle NumberFormatException?

The NumberFormatException in java can be handled in two ways:

1. Using the block try-catch : This involves surrounding the code that might cause the exception with a try block and handling the exception in a catch block. For example:

Output:

2. Using throws keyword : This involves declaring that a method might throw a specific exception and leaving it to the calling method to handle it. For example, a method that parses a string to an integer might declare that it throws a NumberFormatException if the string is not a valid integer. The calling method would then have to handle this exception using a try-catch block or declare that it throws the exception using the throws keyword.

For example:

Output: