== equality check operator working functionality do it use hashcode method internally?

    // Program snippet
 
    String fullName = "AlexAeva";
    System.out.println("fullName hc " +fullName.hashCode());
    
    String firstName = "Alex";
    System.out.println("firstName hc " + firstName.hashCode());
    
    String lastName = "Aeva";
    System.out.println("lastName hc " + lastName.hashCode());
    
    firstName += lastName;
    
    System.out.println("firstName hc " + firstName.hashCode());
    
    // hash code of first name and fullname is same 
    // But equality operator is giving false.
    // DO == use hashcode for  identification internally
    
    
    System.out.println(" == check " + (firstName == fullName));

Result :-

>fullName hc 1684075821
firstName hc 2043454
lastName hc 2037231
firstName hc 1684075821
== check false

Very good observation.

However, it is important to understand the difference between hashcode and .equals.

Hashcode is just the hash of an object. It is useful for defining equality (or rather, proving inequality).

.equals() tells you whether or not ObjectA is considered equal to ObjectB, BASED ON THE OBJECT'S DEFINITION OF equality. One aspect equality might be defined by is the hashcode.

== tells you whether or not ObjectA is literally pointing to and referencing the same data that ObjectB is. Basically, are they the same object.

To give a better example, let's assume that both you and I have a box of 10 sandwiches. A Hashcode would be both of us putting our bags on individual scales and seeing if they weigh the same. .equals() would be opening up the bags to see if they have the same type of sandwiches (down to some arbitrary level of detail). == would be us seeing if we are both holding the same bag.

Consider this:

public class SOQ_20200913_2
{

   public SOQ_20200913_2()
   {
   
   // Program snippet
   
      String fullName = "AlexAeva";
      System.out.println("fullName hc " +fullName.hashCode());
      
      String firstName = "Alex";
      System.out.println("firstName hc " + firstName.hashCode());
      
      String lastName = "Aeva";
      System.out.println("lastName hc " + lastName.hashCode());
      
      firstName += lastName;
      
      System.out.println("firstName hc " + firstName.hashCode());
      
      // hash code of first name and fullname is same 
      // But equality operator is giving false.
      // DO == use hashcode for  identification internally
   
      System.out.println(" hash check " + (firstName.hashCode() == fullName.hashCode()));
      System.out.println(".equals check " + (firstName.equals(fullName)));
      System.out.println(" == check " + (firstName == fullName));
   
   }

   public static void main(String[] args)
   {
   
      SOQ_20200913_2 soq = new SOQ_20200913_2();
   
   }

}

No. == compares objects to reference equality. That is, two objects are equal if and only if they're literally the same. If you want to compare by hash code, you need to call hashCode explicitly. If you want an equality comparison that's at least somewhat reasonable and agrees with hashCode, you can use the equals method.

==, hashcode(), equals()

equals() and == used to compare 2 Objects.here are some of the differences between the two.
== operators for address comparison and .equals() method for content comparison.

equals method to check whether two objects contains the same data or not.

Ex code:

public static void main(String[] args) {
        String s1=new String("Kamal");
        String s2=new String("Kamal");
        String s3=new String("Pasindu");
        
        System.out.println(s1==s2); //false
        System.out.println(s1.equals(s2)); //true
        System.out.println(s1.equals(s3)); //false
    }

In hashcode() method it is return the hashcode value of the Object.

1. If two objects are equal according to equals() method, then their hash code must be same.

public static void main(String[] args) {

        String s1 = new String("Kamal");
        String s2 = new String("Kamal");
        String s3 = new String("Pasindu");

        System.out.println(s1 == s2); //false
        System.out.println(s1.equals(s2)); //true
        System.out.println(s1.equals(s3)); //false

        System.out.println(s1.hashCode() == s2.hashCode()); //true
        System.out.println(s1.hashCode() == s3.hashCode());  //false
    }