Inspecting Methods

The Reflection API allows dynamically locating methods by name and parameter types, and invoking them on object instances.

Method Invocation

To invoke a method: 1. Find the Method object using getDeclaredMethod(name, parameterTypes...). 2. Execute the method using method.invoke(targetInstance, arguments...). 3. If the method is static, pass null as the targetInstance.

Code Walkthrough

This program shows how to invoke a private method with parameters dynamically.

import java.lang.reflect.Method;
class Calculator {
    private int add(int a, int b) {
        return a + b;
    }
}
public class MethodReflectionDemo {
    public static void main(String[] args) throws Exception {
        Calculator calc = new Calculator();
// Get method by name and parameter types
        Method method = Calculator.class.getDeclaredMethod("add", int.class, int.class);
method.setAccessible(true);
// Invoke on instance with arguments
        Integer result = (Integer) method.invoke(calc, 10, 15);
        System.out.println("Result of add method: " + result); // 25
    }
}

Interview-Relevant Information