How to Use Java Reflection getDeclaredMethod() with Class Types

How can I utilize Java Reflection's getDeclaredMethod() with specific class types to access a method?

Class<?> clazz = MyClass.class;
Method method = clazz.getDeclaredMethod("myMethod", String.class);

Java Reflection is a powerful feature in Java that allows you to inspect classes, interfaces, fields, and methods at runtime, without knowing the names of the classes, methods, etc. at compile time. The `getDeclaredMethod()` method is specifically used to retrieve a method by name that is declared in the class represented by this Class object, taking into account the method's parameter types.

try {
    // Obtain the Class object of the desired class
    Class<?> clazz = Class.forName("com.example.MyClass");
    // Retrieve the method named "myMethod" which takes a String parameter
    Method method = clazz.getDeclaredMethod("myMethod", String.class);
    // If it's a private method, you need to make it accessible
    method.setAccessible(true);
    // Optionally invoke the method
    Object instance = clazz.newInstance();
    method.invoke(instance, "Hello Reflection!");
} catch (NoSuchMethodException e) {
    e.printStackTrace();
} catch (IllegalAccessException e) {
    e.printStackTrace();
} catch (InvocationTargetException e) {
    e.printStackTrace();
} catch (InstantiationException e) {
    e.printStackTrace();
}

Causes

• The method might not exist in the specified class.
• The parameter types passed to the method don't match any declared method.
• Access modifiers may restrict visibility of the method.

Solutions

• Ensure that the method name is spelled correctly.
• Check the parameter types and ensure they match the method's signature.
• Use `setAccessible(true)` if the method is private and you want to access it.

Mistake: Forgetting to specify the correct parameter types.

Solution: Double-check the method signature for the parameter types and ensure they match.

Mistake: Not handling exceptions properly after invoking the method.

Solution: Implement a try-catch block to handle potential exceptions such as NoSuchMethodException, IllegalAccessException, etc.

Mistake: Assuming all methods are public.

Solution: If trying to access a private method, remember to set the method's accessibility using setAccessible(true).