How to Fix Java.Lang.StringIndexOutOfBoundsException: String Index Out of Range

This tutorial demonstrates the Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 0 error in Java.

Fix the java.lang.StringIndexOutOfBoundsException: String index out of range Error

The StringIndexOutofBoundsException is an unchecked exception that occurs when accessing the character of a string for which the index is either negative or more than the String length. This exception is also thrown when we use the charAt() method, which is trying to access a character that is not in the String.

Because StringIndexOutofBoundsException is an unchecked exception, it doesn’t need to add to throws of a method or constructor; we can handle it using the try-catch block. Here are the specific scenarios where this exception can occur:

1. When using String.charAt(int index), which will return a character at a given String index. If the index is negative or greater than the String’s length, it will throw the StringIndexOutofBoundsException.
2. When using String.valueOf(char[] data, int offset, int count) which returns a string with given arguments. It will throw the StringIndexOutofBoundsException when any index is negative or offset + count is greater than the size of the array.
3. When using CharSequence.subSequence(int beginIndex, int endIndex) which returns a character sequence. It will throw the StringIndexOutofBoundsException when beginIndex is greater than endIndex, or endIndex is greater than the length of the String.
4. When using String.substring(int beginIndex), which returns a substring from the given String. It will throw the StringIndexOutofBoundsException when beginIndex is negative or greater than the length of the String.
5. When using String.substring(int beginIndex, int endIndex), which returns a sub-string between a specific range. It will throw the StringIndexOutofBoundsException when any index is negative, or endIndex is greater than the length of String of beginIndex is greater than endIndex.

Let’s try an example for StringIndexOutofBoundsException. See example:

package delftstack;

public class Example {
  public static void main(String[] arg) {
    String DemoStr = "delftstack";
    System.out.println(DemoStr.charAt(11));
  }
}

The code above will throw StringIndexOutofBoundsException because there is no character at index 11. See output:

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 11
    at java.base/java.lang.StringLatin1.charAt(StringLatin1.java:48)
    at java.base/java.lang.String.charAt(String.java:1512)
    at delftstack.Example.main(Example.java:7)

The StringIndexOutOfBoundsException can be handled using try-catch blocks. See solution:

package delftstack;

public class Example {
  public static void main(String[] arg) {
    String DemoStr = "delftstack";
    try {
      System.out.println(DemoStr.charAt(11));
    } catch (StringIndexOutOfBoundsException e) {
      System.out.println("Please insert a index under String length: " + DemoStr.length());
    }
  }
}

Now the output for the above code is:

Please insert a index under String length: 10