writing generic function in java

Question

I want to write a function which would return me a Vector of the specified type which I pass to it. For example:

// Here getNewVector(<ClassType>) should return me an integer Vector.
Vector<Integer> myIntVector = getNewVector(Integer.class);
//should get a String vector in this case and so on.
Vector<String> myStringVector = getNewVector(String.class) ;

I want to implement getVector(Class classType) in such a way so as to return a new vector of that particular class type. How can we achieve it without using reflections and by not passing the class name as a String(I would like to pass the class type only as I had mentioned in the example above.)

Actually, I want a function getVector() somewhat like this..

Vector<T> getVector(T t) {
    return new Vector<t>();
}

I'd think twice about using a Vector. Have you considered using a List instead? — KidTempo
– KidTempo, Commented Jun 16, 2012 at 21:17

Tim Pote · Accepted Answer · 2012-06-16 20:03:10Z

8

Take a look at the Java Tutorial for Generic Methods. Here's one way to do what you want:

public static <T> Vector<T> getVector(Class<T> clazz) {
  return new Vector<T>()
}

public static <T> Vector<T> getVector(T t) {
  Vector<T> vector = new Vector<T>();
  vector.add(t);
  return vector;
}

I'm assuming that you're not going to just want to throw away the t you pass into getVector(T t), so I stuck it in the Vector.

Theoretically, you don't need to pass anything into the method if all you want is the typing mechanism:

public static <T> Vector<T> getVector() {
  return new Vector<T>();
}

//Usage
Vector<Integer> vector = getVector();

Java can figure out that you want it typed as a Vector<Integer> from the generic typing on the declaration.

edited Jun 16, 2012 at 20:03

answered Jun 16, 2012 at 19:55

Tim Pote

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Martin Matula · Accepted Answer · 2012-06-16 19:55:19Z

1

public <T> Vector<T> getNewVector(Class<T> type) {
    return new Vector<T>();
}

answered Jun 16, 2012 at 19:55

Martin Matula

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1 Comment

Justin Over a year ago

Seems like that should be a static method.

Louis Wasserman · Accepted Answer · 2012-06-16 21:58:01Z

1

Why even bother writing a function here?

Vector<Integer> myIntVector = new Vector<Integer>();

or, even better, if you're on Java 7,

Vector<Integer> myIntVector = new Vector<>();

(There's no actual difference at runtime, of course, between vector types with different element types.)

answered Jun 16, 2012 at 21:58

Louis Wasserman

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