CODEWITHSUNDEEP
java
Trevor
Trevor

Reputation: 13437

How to call method of class passed as parameter

I'm trying to pass a subclass as a parameter and then create an instance of it, but I'm getting the error message on the line where I instantiate the transformation class (incompatible types). If I try to instantiate using transClass trans = new transClass(), it complains that transClass is unknown. Here's the code I'm using.

abstract class Transformation {
  abstract public Object transform(Object obj);
}
class MyTransformation extends Transformation {
  public Object transform(Object obj){
    // do stuff to obj
    return obj;
  }
}

class AnotherClass {
  public doSomething(Object obj, Class<Transformation> transClass){
    // do more stuff to obj
    Transformation trans = new transClass();  // fails with "Incompatible Types", referring to 'Transformation' and 'transClass'
    // transClass trans = new transClass(); // alternate attempt, also fails with "Unknown Type" on 'transClass'
    return trans.transform(obj);
  }
}

Upvotes: 0

Views: 57

Answers (1)

Luiggi Mendoza
Luiggi Mendoza

Reputation: 85779

You should use Class#newInstance:

public <T extends Transformation> Object doSomething(Object obj, Class<T> transClass)
    throws Exception {
    // do more stuff to obj
    Transformation trans = transClass.newInstance();
    return trans.transform(obj);
}

Upvotes: 5

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