method overriding

[akash azal]

The overriding method must NOT throw checked exceptions that are new
or broader than those declared by the overridden method.

what does this statement means .can anyone explains with example

[Omar Al Kababji]

suppose that you have the following type of exceptions

Exception1 extends Exception
Exception2 extends Exception1
Exception3 extends Exception
RuntimeException1 extends RuntimeException

and that you have a method with the following signature:

public void myMethod() throws Exception1

here is what you can override and what you can't override

//ok since Exception2 is a child of Exception1 (since it extends it)
public void myMethod() throws Exception2

//not ok since Exception3 is not a child of Exception1
public void myMethod() throws Exception3

//ok since RuntimeException1 is not a check exception, although its not a child of Exception1
public void myMethod() throws RuntimeException1

[Paul Stat]

For example

class A {
   void run() throws IOException {}
}
class B extends A {
   void run() throws IOException, NumberFormatException { } //Illegal , should only throw one exception type
   void run() throws Exception { } //Illegal, Exception is broader than IOException
   void run() throws FileNotFoundException { } //OK as FileNotFoundException IS-A IOException
}

[akash azal]

3 runtimeexception 1 is not a child of exception1

then how it is ok

and to know this we have to know the exceptions and subexceptions by heart

[Stephen Davies]

Runtime exception is not a checked Exception

[akash azal]

we have to know about exceptions and subexceptions by heart

[Paul Stat]

You need to know the following for the exam

ArrayIndexOutOfBoundsException
ClassCastException
IllegalArgumentException
IllegalStateException
NullPointerException
NumberFormatException
AssertionError
ExceptionInInitializerError
StackOverflowError
NoClassDefFoundError