boolean check when using Class.fromName

[Meir Yan]

Hello all
i wander if there is away to check if class exists with

Class.fromName("someClassName")

but without throwing exception if class not found but boolean value
thanks

[Ajay Singh]

You can use the following

public boolean exists(String className) {
try {
Thread.currentThread().getContextClassLoader().loadClass(className);
}
catch (ClassNotFoundException e) {
return false;
}
 
return true;
}

[Meir Yan]

hi

i tried to avoid the try/catch

im doing something similar :

try{
    helperObjectClass = Class.forName(helperObjNames.get(i).toString());
}catch(ClassNotFoundException cnf){;}

i was wandering if there is some build in method that returns boolean value

so i could do :

if(Class.forName(helperObjNames.get(i).toString()).isFound){
 
......
}

[Ajay Singh]

i tried to avoid the try/catch

Why? Do *not* remove it. It will not figure out whether class is there.

[Ilja Preuss]

Yes, it would be nice if you could check for the existence of a class without having to relegate to exception handling. Unfortunately, there isn't.

[Jim Yingst]

If all the classes you're interested in come from class files (or jar files containing class files) located on the class path, then you might try something like this:

    public static boolean isClassavailable(String name) {
        String fileName = name.replace(".", "/") + ".class";
        URL resource = ClassLoader.getSystemResource(fileName);
        return resource != null;
    }

Beware that it's not guaranteed to work for all class loaders. Also it doesn't handle nested classes well (can't find java.util.Map.Entry for example). One could fix this making assumptions based on capitalization, but then there's still a problem if you deal with classes that don't follow standard naming conventions. Ultimately, you're probably better off just catching the exception as originally suggested - at least if you want a definite answer.