MyClass.java
 

public class MyClass {
  final int x = 10;

  public static void main(String[] args) {
    MyClass myObj = new MyClass();
    myObj.x = 25; // will generate an error
    System.out.println(myObj.x); 
  }
}

Result:
MyClass.java:6: error: cannot assign a value to final variable x
    myObj.x = 25;
         ^
1 error