How to throw RuntimeException (“cannot find symbol”)

Question

I'm trying to throw an exception in my code like this:

throw RuntimeException(msg);

But when I build in NetBeans I get this error:

C:\....java:50: cannot find symbol
symbol  : method RuntimeException(java.lang.String)
location: class ...
        throw RuntimeException(msg);
1 error

Do I need to import something? Am I misspelling it? I'm sure I must be doing something dumb :-(

Answer 1

throw new RuntimeException(msg);

You need the new in there. It's creating an instance and throwing it, not calling a method.

Answer 2

An Exception is an Object like any other in Java. You need to use the new keyword to create a new Exception before you can throw it.

throw new RuntimeException();

Optionally you could also do the following:

RuntimeException e = new RuntimeException();
throw e;

Both code snippets are equivalent.

Link to the tutorials for completeness.

Answer 3

As everyone else has said, instantiate the object before throwing it.

Just wanted to add one bit; it's incredibly uncommon to throw a RuntimeException. It would be normal for code in the API to throw a subclass of this, but normally, application code would throw Exception, or something that extends Exception but not RuntimeException.

And in retrospect, I missed adding the reason why you use Exception instead of RuntimeException; @Jay, in the comment below, added in the useful bit. RuntimeException isn't a checked exception;

• The method signature doesn't have to declare that a RuntimeException may be thrown.
• Callers of that method aren't required to catch the exception, or acknowlege it in any way.
• Developers who try to later use your code won't anticipate this problem unless they look carefully, and it will increase the maintenance burden of the code.

Answer 4

you will have to instantiate it before you throw it

throw new RuntimeException(arg0) 

PS: Intrestingly enough the Netbeans IDE should have already pointed out that compile time error

Answer 5

throw new RuntimeException(msg); // notice the "new" keyword

Answer 6

You need to create the instance of the RuntimeException, using new the same way you would to create an instance of most other classes:

throw new RuntimeException(msg);

Answer 7

Just for others: be sure it is new RuntimeException, not new RuntimeErrorException which needs error as an argument.

Answer 8

throw new RuntimeException(msg);

unlike any other Exceptions I think RuntimeException is the only one that will not stall the program but it can still keep running and recover just print out a bunch of Exception lines? correct me if I am wrong.

Answer 9

using new keyword we always create a instance (new object) and throwing it , not called a method

throw new RuntimeException("Your Message");

You need the new in there. It's creating an instance and throwing it, not calling a method.

int no= new Scanner().nextInt();   // we crate an instance using new keyword and throwing it 

using new keyword memory clean [because use and throw]

new Handler().postDelayed(new Runnable() {
    @Override
    public void run() {

        //do your work here..
    }
}, 1000);