java.lang.NumberFormatException – How to solve Java NumberFormatException

In this example we are going to talk about how to solve the java.lang.numberformatexception . NumberFormatException in java is discussed in this article. This exception can occur in java applications, web applications, and mobile applications. This can happen in Java, JSP, Servlet, and Android code. This is a common error or failure which happens in an application. It is an unchecked exception. Unchecked Exception is not caught during compile time checking. This exception need not be declared in the method’s signature. It is a run time exception and validation is required by the developer to handle this error. The other common failures are NullPointerException and NoClassDefFoundError.

The class diagram below shows the catch numberformatexception Class hierarchy.

Catch numberformatexception happens while converting a String into different data types such as integer, float, double, long, short, and byte types. The methods below are related to the conversion are :

Different reasons for NumberFormatException are listed below:

• String to be converted is null
• The length of the string is zero
• The string has no numeric characters
• The value of the string does not represent an Integer
• The string can be empty
• It can have trailing space
• It can have a leading space
• The string can be alphanumeric
• The string value might be out of the data type supported range
• The string value and the method used for conversion might be for different data types.

The sequence diagram below shows the possible scenario when a NumberFormatException can happen.

Integer class has the methods shown below, which can throw NumberFormatException.

• Integer(String s) – Constructor
• decode(String s)
• parseInt(String s)
• parseInt(String s, int radix)
• valueOf(String s)
• valueOf(String s, int radix)

Below are the code examples showing the conversion of string to other data types such as int, float, double, long, short, and byte.

 1.Prerequisites

Java 7 or 8 is required on the linux, windows or mac operating system.

2. Download

You can download Java 7 from Oracle site. On the other hand, You can use Java 8. Java 8 can be downloaded from the Oracle web site .

3. Setup

You can set the environment variables for JAVA_HOME and PATH. They can be set as shown below:

Setup

JAVA_HOME="/desktop/jdk1.8.0_73"
export JAVA_HOME
PATH=$JAVA_HOME/bin:$PATH
export PATH

4. String Conversion to Int

Here is a simple program that will attempt to convert a String to an int. The code below is converting a string of value 0.78 to an Integer.

String to Int

public class StringIntegerConversionExample
{
  public static void main(String[] args)
    {
      int value = Integer.parseInt("0.78");
      
      System.out.println(value);
    }
}

The above code is executed by using the command below:

StringIntegerConversionExample

javac StringIntegerConversionExample.java
java StringIntegerConversionExample

The output is shown below in the attached screen.

You can change the value to “78”. The code is shown below

String to Int

public class StringIntegerConversionExample
{
  public static void main(String[] args)
    {
      int value = Integer.parseInt("78");
      
       System.out.println(value);
    }
}

The above code is executed by using the command below:

StringIntegerConversionExample

javac StringIntegerConversionExample.java
java StringIntegerConversionExample

The output is shown below in the attached screen.

You can change the value to “check”. The code is shown below after the change

String to Int

public class StringIntegerConversionExample
{
  public static void main(String[] args)
    {
      Integer.parseInt("check");
    }
}

The above code is executed by using the command below:

StringIntegerConversionExample

javac StringIntegerConversionExample.java
java StringIntegerConversionExample

The output is shown below in the attached screen.

5. String Conversion to Float

Here is a simple program that will attempt to convert a String to a float. The code below is converting a string of value “798!89” to a Float.

String to Float

public class StringFloatConversionExample
{
  public static void main(String[] args)
    {
      Float.parseFloat("798!89");
    }
}

The above code is executed by using the command below:

StringFloatConversionExample

javac StringFloatConversionErrorExample.java
java StringFloatConversionExample

The output is shown below in the attached screen.

You can change the value to “798.89”. The code is shown below

String to Float

public class StringFloatConversionExample
{
  public static void main(String[] args)
    {
      float value =  Float.parseFloat("798.89");
      
      System.out.println(value);
    }
}

The above code is executed by using the command below:

StringFloatConversionWorkingExample

javac StringFloatConversionExample.java
java StringFloatConversionExample

The output is shown below in the attached screen.

6. String Conversion to Double

Here is a simple program that will attempt to convert a String to a double. The code below is converting a string of value “two.two” to a double.

String to Double

public class StringDoubleConversionExample
{
  public static void main(String[] args)
    {
      double aDoublePrim = Double.parseDouble("two.two");
    }
}

The above code is executed by using the command below:

StringDoubleConversionErrorExample

javac StringDoubleConversionExample.java
java StringDoubleConversionExample

The output is shown below in the attached screen.

You can change the value to “2.2”. The code is shown below:

String to Double

public class StringDoubleConversionExample
{
  public static void main(String[] args)
    {
      double value = Double.parseDouble("2.2");
      System.out.println(value);
    }
}

The above code is executed by using the command below:

StringDoubleConversionExample

javac StringDoubleConversionExample.java
java StringDoubleConversionExample

The output is shown below in the attached screen.

7. String Conversion to Long

Here is a simple program that will attempt to convert a String to a long. The code below is converting a string of value “64403L” to a long.

String to Long

public class StringLongConversionExample
{
  public static void main(String[] args)
    {
      Long decodedLong = Long.decode("64403L");
    }
}

The above code is executed by using the command below:

StringLongConversionErrorExample

javac StringLongConversionExample.java
java StringLongConversionExample

The output is shown below in the attached screen.

You can change the value to “64403”. The code is shown below:

String to Long

public class StringLongConversionExample
{
  public static void main(String[] args)
    {
      Long value = Long.decode("64403");
      
      System.out.println(value);
    }
}

The above code is executed by using the command below:

StringLongConversionExample

javac StringLongConversionExample.java
java StringLongConversionExample

The output is shown below in the attached screen.

8. String Conversion to Short

Here is a simple program that will attempt to convert a String to a short. The code below is converting a string of value “2 ” to a short.

String to Short

public class StringShortConversionExample
{
  public static void main(String[] args)
    {
      Short shortInt = new Short("2 ");
    }
}

The above code is executed by using the command below:

StringShortConversionErrorExample

javac StringShortConversionExample.java
java StringShortConversionExample

The output is shown below in the attached screen.

You can change the value to “2” (trimming the spaces). The code is shown below:

String to Short

public class StringShortConversionExample
{
  public static void main(String[] args)
    {
      Short shortInt = new Short("2 ".trim());
    }
}

The above code is executed by using the command below:

StringShortConversionExample

javac StringShortConversionExample.java
java StringShortConversionExample

The output is shown below in the attached screen.

9. String Conversion to Byte

Here is a simple program that will attempt to convert a String to a byte. The code below is converting a string of value “200” to a byte.

String to Byte

public class StringByteConversionExample
{
  public static void main(String[] args)
    {
      Byte.parseByte("200");
    }
}

The above code is executed by using the command below:

StringByteConversionErrorExample

javac StringByteConversionExample.java
java StringByteConversionExample

The output is shown below in the attached screen.

You can change the value to “20” (within the range of -128 to 127). The code is shown below:

String to Byte

public class StringByteConversionExample
{
  public static void main(String[] args)
    {
      Byte.parseByte("20");
    }
}

The above code is executed by using the command below:

StringByteConversionExample

javac StringByteConversionExample.java
java StringByteConversionExample

The output is shown below in the attached screen.

10. How to solve the java.lang.NumberFormatException

NumberFormatException is thrown when a string is converted to a numeric value. The string format needs to be in the right format of the numeric type. It will fail if the format is wrong. The first step is to check the string for null value. You should trim the blank spaces of the string. If there are multiple numbers with a delimiter space, split the strings.

In any case, the NumberFormatException is handled by using try catch finally block.

Handling NumberFormatException

public class NumberFormatExceptionHandlingExample
{
  
  
    public static void main(String[] args)
    {
        try
        {
            float value = Float.valueOf("978!79);  
          
            System.out.println("Parsed value is"+value);
        }
        catch(NumberFormatException exception)
        {
            System.err.println("Wrong float value");
            
        }   
        finally
        {
        }
    }
}

The above code is executed by using the command below:

NumberFormatExceptionHandlingExample

javac NumberFormatExceptionHandlingExample.java
java NumberFormatExceptionHandlingExample

The output is shown below the numberformatexception java in the attached screen.

11. Download the Source Code

Last updated on Oct. 07, 2019

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