call static method given a class object in java

Question

If

class MyClass {
    public static void main(String[] str) {
        System.out.println("hello world");
    }
}

// in some other file and method
Class klass = Class.forName("MyClass");

How can I call MyClass.main? I do not have the string "MyClass" at compile time, so I cannot simply call MyClass.main(String[]{}).

Reflection and class loading can do this. Can you tell us the motivation behind this? — Hovercraft Full Of Eels
– Hovercraft Full Of Eels, Commented Jan 28, 2012 at 3:45

Aravind Yarram · Accepted Answer · 2012-01-28 03:46:08Z

51

You use reflection to invoke methods (or create objects etc). Below is a sample to invoke main() method in MyClass. All you need to make sure is that MyClass is in the classpath.

Class<?> cls = Class.forName("MyClass");
Method m = cls.getMethod("main", String[].class);
String[] params = null; 
m.invoke(null, (Object) params);

answered Jan 28, 2012 at 3:46

Aravind Yarram

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2 Comments

Stephen C Over a year ago

I would NOT call a main entry-point method passing it a null argument. The java launcher calls main with an empty array if there are no command line arguments, and most main methods don't bother to check for null.

Aravind Yarram Over a year ago

@StephenC thanx for the info on java launcher. I didn't know that.

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