Algorithm

  1. Import necessary packages:

    • Import java.lang.reflect.Field for accessing fields.
    • Import java.lang.reflect.Method for accessing methods.

  2. Create an instance of the class with private members:

    • Instantiate the class for which you want to access private members.

  3. Access private fields:

    • Use the getDeclaredField method of the Class class to obtain the Field object for the private field.
    • Set the field accessible by calling setAccessible(true) on the obtained Field object.
    • Use the get method on the field to retrieve its value.

  4. Access private methods:

    • Use the getDeclaredMethod method of the Class class to obtain the Method object for the private method.
    • Set the method accessible by calling setAccessible(true) on the obtained Method object.
    • Use the invoke method on the method to execute it.

  5. Handle exceptions:

    • Handle NoSuchFieldException, IllegalAccessException, NoSuchMethodException, and other relevant exceptions that may be thrown during reflection.

 

Code Examples

#1 Code Example- Access private fields using getter and setter methods

Code - Java Programming

class Test {

  // private variables
  private int age;
  private String name;

  // initialize age
  public void setAge(int age) {
    this.age = age;
  }

  // initialize name
  public void setName(String name) {
    this.name = name;
  }

  // access age
  public int getAge() {
    return this.age;
  }

  // access name
  public String getName() {
    return this.name;
  }

}

class Main {
  public static void main(String[] args) {
    // create an object of Test
    Test test = new Test();

    // set value of private variables
    test.setAge(24);
    test.setName("Devsenv");

    // get value of private variables
    System.out.println("Age: " + test.getAge());
    System.out.println("Name: " + test.getName());
  }
}
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Output

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Age: 24 Name: Devsenv

#2 Code Example- Access the private field and method using Reflection

Code - Java Programming

import java.lang.reflect.*;

class Test {

  // private variables
  private String name;

  // private method
  private void display() {
    System.out.println("The name is " + name);
  }

}

class Main {
  public static void main(String[] args) {
    try {
      // create an object of Test
      Test test = new Test();

      // create an object of the class named Class
      Class obj = test.getClass();

      // access the private variable
      Field field = obj.getDeclaredField("name");
      // make private field accessible
      field.setAccessible(true);

      // set value of field
      field.set(test, "Devsenv");

      // get value of field
      // and convert it in string
      String value = (String)field.get(test);
      System.out.println("Name: " + value);

      // access the private method
      Method[] methods = obj.getDeclaredMethods();
      System.out.println("Method Name: " + methods[0].getName());
      int modifier = methods[0].getModifiers();
      System.out.println("Access Modifier: " + Modifier.toString(modifier));

    }
    catch(Exception e) {
      e.printStackTrace();
    }
  }
}
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Output

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Name: Devsenv
Method Name: display
Access Modifier: private
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Demonstration

Java Programing Example to Access private members of a class-DevsEnv