mAuth.createUserWithEmailAndPassword(email,password)
     .addOnCompleteListener(new OnCompleteListener<AuthResult>() {
        @Override
        public void onComplete(@NonNull Task<AuthResult> task) {

            if (task.isSuccessful())
            {
                user user=new user(
                nameOfUser,
                email,
                phNo
                );
                //Toast.makeText(Register_User.this, "Working", Toast.LENGTH_SHORT).show();

                mData.getReference("Users")
                        .child(Objects.requireNonNull(FirebaseAuth.getInstance().getCurrentUser()).getUid())
                        .push().setValue(user).addOnCompleteListener(new OnCompleteListener<Void>() {

                    @Override
                    public void onComplete(@NonNull Task<Void> task) {
                        progressBar.setVisibility(View.GONE);

                        Toast.makeText(Register_User.this, "Upto here", Toast.LENGTH_LONG).show();
                        if (task.isSuccessful()) {
                            Toast.makeText(Register_User.this, "Successfully Registered", Toast.LENGTH_SHORT).show();
                        } else {
                            Toast.makeText(Register_User.this, "Failed to Registered", Toast.LENGTH_SHORT).show();
                        }
                    }
                });
            }
            else if (task.getException() instanceof FirebaseAuthUserCollisionException) {
                progressBar.setVisibility(View.GONE);
                Toast.makeText(getApplicationContext(), "You are already registered", Toast.LENGTH_SHORT).show();
            }
        }
    });