Java Exceptions

When to use Errors and Exceptions

An Error is a subclass of Throwable that indicates serious problems that a reasonable application should not try to catch. Most such errors are abnormal conditions.

(Source: Javadoc)

How to throw an exception

public void myMethod( String s ) {
  if (!isStringValid(s)) {
    throw new IllegalArgumentException("This string is not valid!");
  }
}

Common Exceptions

• IllegalArgumentException: One argument of the current method hasn't the form it should have.
• IllegalStateException: The current object is in the wrong state.
• NullPointerException: A Null-Pointer was given, but it should have been an object.

A long list of Exceptions is on Hai's Blog.

See also

• http://docs.oracle.com/:
  • Class Exception