How to Instantiate Generic Types in Java at Runtime?

Instantiating Generic Types in Java

Although it may appear straightforward to instantiate generic types in Java, it poses a unique challenge. This article explores the intricacies of this task and provides a comprehensive solution.

Consider the following class declaration:

public class Abc<T> {
    public T getInstanceOfT() {
        // Create and return an instance of type T
    }
}

The goal is to create an instance of the generic type T within the method getInstanceOfT(). However, the erasure of type information during compilation makes it impossible to determine the actual type of T from the bytecode.

Resolving the Challenge

To solve this problem, we need to pass the actual type of T as a runtime argument. This can be achieved by modifying the class declaration to:

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

The method now takes a Class object as an argument, which represents the actual type of T to instantiate. This allows us to use reflection to create an instance of the desired type.

Note that exception handling is necessary to manage any errors during instantiation.

Conclusion

Instantiating generic types in Java involves passing the actual type information at runtime, as it cannot be inferred from the bytecode. By utilizing the Class object and reflection, it is possible to create instances of generic types dynamically.

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