How to throw RuntimeException (“cannot find symbol”)

问题

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 :-(

回答1:

throw new RuntimeException(msg);

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

回答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.

回答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.

回答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

回答5:

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

回答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);

回答7:

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

回答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.

回答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);

来源：https://stackoverflow.com/questions/3406219/how-to-throw-runtimeexception-cannot-find-symbol

标签

java

exception-handling

runtimeexception