AWS Cognito ANDROID-SDK for creating User

create_user.java

// create a handler for registration 
SignUpHandler handler = new SignUpHandler() {
    @Override
    public void onSuccess(CognitoUser user, CognitoUserCodeDeliveryDetails codeDeliveryDetails) {
        // If the sign up was successful, "user" is a CognitoUser object of the user who was signed up.
        // "codeDeliveryDetails" will contain details about where the confirmation codes will be delivered.
}

    @Override
    public void onFailure(Exception exception) {
        // Sign up failed, code check the exception for cause and perform remedial actions.
    }
}