Question about a warning re:Generics in Java

JC 2K3

I'm writing Java using Eclipse, and it's giving me a warning if I try to declare a Generic class without parameterising it. Thing is, I don't want to parameterise it until I instantiate it later on in the program, for example, say I have a generic class, "MyClass", which takes one parameter, and I want to do something like this:

public static void main(String args[]){
	Terminal terminal = new Terminal();
	MyClass myclass; 		//Eclipse warns me here

	
	switch(terminal.readInt()){	//read an int from the user
		case 1:
			myclass = new MyClass<Integer>();
		break;

		case 2:
			myclass = new MyClass<String>();
		break;
	}
}

Now this runs fine, so should I just ignore the warning or is there something I'm doing that's fundamentally wrong here?

EDIT: Ok, I realise I can write '"MyClass<?> myclass" when declaring it, and there'll be no warnings in this code, however, this seems to mean I can't pass any non-null parameters to any methods I might call on myclass later on in my program... :S

Tobias Greeshman

I'm guessing you're using java 5 at least here.

One thing you can do is use wildcards in your definition to allow the class have any Object paramaterised. This should shut up eclipse. The warning is no harm anyways.

class MyClass <T> {
  // ...
}

// ...

  public static void main(String[] args) {

     MyClass <? extends Object> my;

     my = new MyClass<String>();

  }

JC 2K3

Yeah, I know I can use a wildcard, but then that stops me from passing non-null parameters to methods taking generic parameters.

For example:

class MyClass <T> {
  private T thing;

  public setThing(T thething){
    thing = thething;
  }
}

// ...

  public static void main(String[] args) {

     MyClass <? extends Object> my;

     my = new MyClass<String>();

[COLOR="Red"]     my.setThing("This is a string");    //I get an error here[/COLOR]

  }

I'm guessing ignoring the warning I get when I don't parameterise is the way forward....

Civilian_Target

Well... if you're not going to strongly type it, why use wildcards? Just declare it regular 1.4 style!