How to determine by reflection if a Method returns 'void'

java reflection methods
Pablo Fernandez picture Pablo Fernandez · Dec 17, 2009 · Viewed 34.3k times · Source

I have a java.lang.reflect.Method object and I would like to know if it's return type is void.

I've checked the Javadocs and there is a getReturnType() method that returns a Class object. The thing is that they don't say what would be the return type if the method is void.

Thanks!

Answer

OscarRyz picture OscarRyz · Dec 17, 2009 
if( method.getReturnType().equals(Void.TYPE)){
    out.println("It does");
 }

Quick sample:

$cat X.java  

import java.lang.reflect.Method;


public class X {
    public static void main( String [] args ) {
        for( Method m : X.class.getMethods() ) {
            if( m.getReturnType().equals(Void.TYPE)){
                System.out.println( m.getName()  + " returns void ");
            }
        }
    }

    public void hello(){}
}
$java X
hello returns void 
main returns void 
wait returns void 
wait returns void 
wait returns void 
notify returns void 
notifyAll returns void

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