How does Java reflection mechanism call methods?

The reflection mechanism allows the program to call methods at runtime. The steps are as follows: Get the class object and get the method object. Call the method, passing in the object instance and parameters. Use reflection to call the getName() method of the Employee class and return "John Doe".

Java reflection mechanism calls methods

The Java reflection mechanism allows the program to obtain and modify class information and behavior at runtime. It is widely used in frameworks, testing and debugging tools.

Use the reflection calling method

You can use the reflection calling method through the following steps:

1. Get the Class object: Use Class.forName() to get the Class object of the class.
2. Get the method object: Use getMethod() or getMethods() to get the Method object of the method.
3. Invoking the method: Use the invoke() method to call the method, passing in the object instance and parameters (if any).

Syntax

Method method = Class.forName("ClassName").getMethod("methodName", parameterTypes);
Object result = method.invoke(objectInstance, parameters);

Where:

• ClassName is the class name to be called.
• methodName is the name of the method to be called.
• parameterTypes is an array of method parameter types.
• objectInstance is the object instance on which the method is to be called (if the method is a non-static method).
• parameters is the array of parameters to be passed to the method.

Practical case

Suppose there is a Employee class with the following methods:

public class Employee {
    public String getName() {
        return "John Doe";
    }
}

Now, let We use the reflection mechanism to call the getName() method:

Class<?> employeeClass = Class.forName("Employee");
Method getNameMethod = employeeClass.getMethod("getName");
String name = (String) getNameMethod.invoke(new Employee());
System.out.println(name); // 输出：John Doe

In this example, we first obtain the Class object of the Employee class. Then, we get the Method object for the getName() method. Finally, we create an instance of the Employee object and call the getName() method using reflection.

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