How to Instantiate a Generic Type in Java with a Class Parameter?

Instantiating Generics Type in Java with Class Parameter

Generics in Java provide a convenient way to define classes and methods that operate on a variety of data types. However, instantiating an object of a generic type can be a bit tricky.

Suppose you have a class declaration like this:

public class Abc<T> {
    public T getInstanceOfT() {
        // I want to create an instance of T and return the same.
    }
}

How can you create an object of type T in the getInstanceOfT method?

Solution:

The key to instantiating a generic type is to pass the actual type as an argument to the generic class. This can be done using the Class type parameter:

public class Abc<T> {
    public T getInstanceOfT(Class<T> aClass) {
        return aClass.newInstance();
    }
}

In this modified code, the getInstanceOfT method accepts an argument of type Class, which represents the actual type of the object to be created. The newInstance() method on the Class object then creates an instance of that type and returns it.

Exception Handling:

It's important to note that you'll need to add exception handling to your code, as newInstance() can throw an InstantiationException or IllegalAccessException.

Runtime Type:

Passing the actual type as an argument is necessary because the type of T is not known at compile time. After compilation, the byte code doesn't contain any information about the actual type, so it must be provided explicitly at runtime.

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