Exception

[Shalini Srivastav]

Hello
It is valid to throw RuntimeException then why doesn't it compile ?

class Null{
	static{
		throw new NullPointerException();
	}
}

[Sagar Rohankar]

Whats the compilation error? Can you draw some conclusion from it why its not allowed to explicitly throw runtime exception from _initialization_ block.

[Shalini Srivastav]

Null.java:3: error: initializer must be able to complete normally
static{
^
1 error

I know this that we can throw unchecked exception in static initilizer block to get an ExceptionInInitializerError but not checked exceptions,so what's wrong here ?

[Rob Spoor]

It seems the compiler is smart enough to see that if that class is initialized, it will always cause an error. Why would you want such a class anyway? Once you try to load it your JVM will exit.

[Shalini Srivastav]

Rob Spoor wrote:It seems the compiler is smart enough to see that if that class is initialized, it will always cause an error. Why would you want such a class anyway? Once you try to load it your JVM will exit.

class Null{  
    static{ 
    if(true)
           throw new NullPointerException();  
    }  
} 

why does it work ? it is also an explicit exception declaration for compiler.

[Rob Spoor]

Because the compiler is not smart enough to see that an if (true) will always have its body executed. If you search this forum there are some discussions about that.

[Shalini Srivastav]

Rob Spoor wrote:It seems the compiler is smart enough to see that if that class is initialized, it will always cause an error. Why would you want such a class anyway? Once you try to load it your JVM will exit.

Rob Spoor wrote:Because the compiler is not smart enough to see that an if (true) will always have its body executed. If you search this forum there are some discussions about that.

Sometimes you say compiler is enough smart and sometimes you say compiler is not enough smart lol.I am not kid.

[Campbell Ritchie]

Before you call compilers smart or not smart, you ought to try writing one. Picking up that sort of path through the code is difficult. So there are some things which a compiler cannot readily be programmed to handle.