CODEWITHSUNDEEP
javatry-catch
Srikanth Balaji
Srikanth Balaji

Reputation: 2718

try block with empty finally block

When we have a try block without any code is finally block, the compiler compiles it fine. However, there is no purpose of try here - because we are neither catching a exception nor cleaning up code in finally block.

public int updateTable(InputVo sfVo){
    //SqlSession session = ConnFactory.getSqlSession();
    //InputMapper spMapper = session.getMapper(InputMapper .class);
    int updRecs=0;
    try {

        mapper.updateData(sfVo);    

        updRecs=sfVo.getRecsUpdated();
        return updRecs;

    } finally {
        //session.close();
    }
}

If thats the case, why does JAVA has not considered a compile time check on this ?

Wouldn't be better if compiler throws error at compile time itself - like "Cannot have a empty finally block"

Upvotes: 2

Views: 4426

Answers (3)

AxelH
AxelH

Reputation: 14572

To add some context, finally is just keyword/label to identify a block statement linked to the try. It's like a goto that is called in the try.

Every block statement can be empty.

if(true){}
--
while(true){}
--
public void method(){}

even this is valid

public void method(){
    {}
}

So, we could say that the compiler don't care about the content of those, only the syntax in it.

Upvotes: 2

Turtle
Turtle

Reputation: 1656

Since you surrounded your exception-throwing code in a try-catch or try-finally statement, the compiler knows you processed the potential error. What you do with it is up to you, it is authorized to ignore it.

You could argue: "How is that different than no try at all?". The difference is that if you don't put it in a try clause, the compiler can't know if you did it on purpose or you forgot it.

Basically, catching an exception is mandatory, but processing it isn't.

Upvotes: 0

davidxxx
davidxxx

Reputation: 131356

Using a try-finally statement without declaring a catch statement is legal.

From the JLS :

14.20.2. Execution of try-finally and try-catch-finally

A try statement with a finally block is executed by first executing the try block. Then there is a choice:

If execution of the try block completes normally, then the finally block is executed, and then there is a choice:

If the finally block completes normally, then the try statement completes normally.

If the finally block completes abruptly for reason S, then the try statement completes abruptly for reason S.

You said :

we are neither catching a exception nor cleaning up code in finally block. If thats the case, why does JAVA has not considered a compile time check on this ?

What you write in the finally statement is of course at the hand of the developer.
Having a empty finally statement is useless but it is the same thing that having an empty if or for statement.
These are helpless but the compiler will not complain about it as it stays valid code in terms of compilation.
However, IDEs could emit warnings about it to point bad smells.

Upvotes: 6

Related Questions