実行時に Java でジェネリック型をインスタンス化するにはどうすればよいでしょうか?

Instantiating Generic Types in Java: A Comprehensive Guide

Instantiating generic types in Java can be a challenging task for newcomers. In this article, we'll explore the problem and provide a detailed solution that uses class instantiation.

Suppose you have a generic class Abc with a method getInstanceOfT that aims to create an instance of the type parameter T. However, since generic types are erased at compile time, it can be difficult to instantiate them without specifying the actual type at runtime.

To overcome this challenge, we need a way to pass the actual type to the getInstanceOfT method. One approach is to modify the method signature to include the type parameter as an additional parameter, as shown below:

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

The Class parameter allows you to specify the actual type of T at runtime. The aClass.newInstance() method then creates a new instance of the specified type and returns it.

It's important to note that you'll have to add exception handling to account for any runtime errors that may occur during instantiation. Additionally, since the actual type is not part of the bytecode, you must explicitly provide it when instantiating the generic type.

In conclusion, instantiating generic types in Java requires a bit of finesse. By passing the actual type as a parameter to the generic method, you can dynamically create instances of generic types and leverage their powerful capabilities in your Java programs.

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