Java String FAQ: How do I convert a String to an int with Java?

Answer: You can convert a Java String to an int using the parseInt() method of the Java Integer class. This method serves the purpose of converting a Java String to int data type. Let's take a look at an example.

Java String to int example

Here's the source code for a complete example program that demonstrates this Java "String to int" conversion process:

public class JavaStringToIntExample
{
  public static void main (String[] args)
  {
    // String s = "fred";    // use this if you want to test the exception below
    String s = "100";

    try
    {
      // the String to int conversion happens here
      int i = Integer.parseInt(s.trim());

      // print out the value after the conversion
      System.out.println("int i = " + i);
    }
    catch (NumberFormatException nfe)
    {
      System.out.println("NumberFormatException: " + nfe.getMessage());
    }
  }
}

Java String to int - discussion

As you can see from this example Java String to int class, the Integer.parseInt(s.trim()) method is used to convert from the String s to the int i in this line of code:

int i = Integer.parseInt(s.trim());

If the conversion attempt fails -- for instance, if you try to convert the Java String "fred" to an int -- the parseInt method will throw a NumberFormatException, which you should handle in a try/catch block.

In this example, I don't really need to use the trim() method of the Java String class, but in a real-world program you should use it, so that's why I show it here.

Other Java String to int conversion notes

While I'm in the Java String to int neighborhood, here are a few related notes about Java and the String and Integer classes:

• Integer.toString(int i) is used to convert in the other direction, from a Java into to a Java String.
• If you're interested in converting a String to an Integer object, use the valueOf() method of the Integer class instead of the parseInt() method.

I hope this "Java String to int" example is helpful. If you have any questions or comments, just leave a note in the Comments section below.