How Can I Invoke a Generic Java Method with Runtime Type Arguments?

Calling Generic Methods with Run-Time Type Arguments

Problem:

You want to invoke a generic method dynamically, specifying the type argument at run-time. However, Java does not allow direct type argument resolution in generic method invocations.

Solution:

To achieve this, use Java reflection:

// Get the generic method
Method<T> method = MyTestClass.class.getMethod("myGenericMethod");

// Create a type array for the type arguments
Type[] typeArguments = { new TypeReference<T>() {}.getType() };

// Make the generic method specific
Method<T> specificMethod = method.makeGenericMethod(typeArguments);

// Invoke the specific method with an instance and parameters
T result = specificMethod.invoke(myInstance, parameters);

Explanation:

1. Obtain the Generic Method: Use getMethod() to retrieve the generic method from the class.
2. Create Type Array: Create a Type[] array to hold the type arguments for the generic method.
3. Generate the Specific Method: Use makeGenericMethod() to create a new method instance with the specified type arguments.
4. Invocation: Invoke the specific method using invoke() with the instance and parameters.

Additional Notes:

• You can use newInstance() to create a new instance of the generic type from the interface.
• Reflection allows dynamic resolution of type arguments at run-time.
• Generics provide compile-time type checking, but reflection allows flexibility in dynamic scenarios.

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