Java Reflection Examples

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1. How to invoke or access a private method of an object or class in java

package basics;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

class ReflectionExample {

 /**
  * Invokes a private method of an object using java Reflection.
  */
 public void invokePrivateMethod() {

  //Class instance
  Class personClass = Person.class;

  // Get methods
  Method[] methods = personClass.getDeclaredMethods();

  // Create the object to invoke the methods on
  Person computer = new Person("Ivan");

  if(methods.length>0)
  {
   try {
    
    //This is very important to invoke a private method
    // or to access a private variable
    methods[0].setAccessible(true);
    
    methods[0].invoke(computer, null);
   } catch (IllegalArgumentException ex) {
    ex.printStackTrace();
    return;
   } catch (InvocationTargetException ex) {
    ex.printStackTrace();
    return;
   } catch (IllegalAccessException ex) {
    ex.printStackTrace();
    return;
   }
  }
 }

 public static void main(String[] args) {
  new ReflectionExample().invokePrivateMethod();
 }
}

class Person {
 private String name;

 public Person(String name) {
  this.name = name;
 }

 private void sayName() {
  System.out.println("My name is : " + name);
 }

}

The out put will be:

My name is : Ivan