Program to demonstrate working of Field class in Java Reflection API for getting field, setting and getting its value
Output of the program :
package com.hubberspot.example;
import java.lang.reflect.Field;
class Customer {
public String firstname;
public String lastname;
public String email;
public static int counter;
}
public class FieldDemo {
public static void main(String[] args) {
// Create a test object. We can create
// and apply reflection on any class
// we want without knowing which fields
// it has. We are taking Customer here.
Customer customer = new Customer();
// Getting Class associated with Customer
Class demo = customer.getClass();
try {
// Using Field class we can get field of any
// class we want. Here we are getting field
// firstname by calling getField method of the
// Class associated with Customer
Field field = demo.getField("firstname");
// After getting the field we are assigning it
// with a value by using set method of Field
// First parameter is the Object of Customer and
// second parameter is the value we want to set
field.set(customer, "Jonty");
// After assignment we are getting the value back
// by using get method of Field and passing the
// Object of Customer for which we want the value
Object result = field.get(customer);
// printing it to console
System.out.println("Customer First Name is : "
+ result);
// similarly doing for lastname and email
field = demo.getField("lastname");
field.set(customer, "Magicman");
result = field.get(customer);
System.out.println("Customer Last Name is : "
+ result);
field = demo.getField("email");
field.set(customer, "Jonty@Magic.com");
result = field.get(customer);
System.out.println("Customer Email is : "
+ result);
field = demo.getField("counter");
// while working with static we are not passing
// Object as Customer instance but we are
// passing it a null because its static field
field.set(null, 1);
result = field.get(null);
System.out.println("Customer Counter is : "
+ result);
} catch (SecurityException e) {
e.printStackTrace();
} catch (NoSuchFieldException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
}
Output of the program :