Validate user-email and password before performing login operation

credential-validation.java

    /**
     * Validate user email and password 
     * Email and password EditText fields are wrapped inside TextInputLayout
     *
     * @return true if email and password are valid, otherwise false
     */
    private boolean isCredentialsValid() {
        String emailAddress = edtEmail.getText().toString().trim();
        String password = edtPassword.getText().toString();
        if (TextUtils.isEmpty(emailAddress)
                || !android.util.Patterns.EMAIL_ADDRESS.matcher(emailAddress).matches()) {
            edtEmailWrapper.setError("Enter valid email!");
            return false;
        } else if (TextUtils.isEmpty(password)) {
            edtPasswordWrapper.setError("Enter password");
            return false;
        }
        return true;
    }