Pick date and time and save in SharedPreferences

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        android:textSize="25dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="PICK TIME"
        android:textSize="25dp"
        app:layout_constraintBottom_toTopOf="@+id/textView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

package com.example.dialog;

import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.DialogFragment;

import android.app.DatePickerDialog;
import android.app.Dialog;
import android.app.TimePickerDialog;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.text.format.DateFormat;
import android.view.View;
import android.widget.Button;
import android.widget.DatePicker;
import android.widget.TextView;
import android.widget.TimePicker;

import java.util.Calendar;

public class MainActivity extends AppCompatActivity {

    static SharedPreferences sp;
    static Calendar now = Calendar.getInstance();
    static String date_time = "";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button button1 = findViewById(R.id.button);

        sp = getSharedPreferences("sp", MODE_PRIVATE);

        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                MyDatePickerFragment fragment1 = new MyDatePickerFragment();
                fragment1.show(getSupportFragmentManager(), "dp");
            }
        });
    }

    public static class MyDatePickerFragment extends DialogFragment implements DatePickerDialog.OnDateSetListener {
        @Override
        public Dialog onCreateDialog(Bundle savedInstanceState) {
            int y, m, d = 0;
            if (sp.getString("year", ""). equals("")){
                y = now.get(Calendar.YEAR);
            } else {
                y = (int)Double.parseDouble(sp.getString("year", ""));
            }
            if (sp.getString("month", ""). equals("")){
                m = now.get(Calendar.MONTH);
            } else {
                m = (int)Double.parseDouble(sp.getString("month", ""));
            }
            if (sp.getString("day", ""). equals("")){
                d = now.get(Calendar.DAY_OF_MONTH);
            } else {
                d = (int)Double.parseDouble(sp.getString("day", ""));
            }

            return new DatePickerDialog(getActivity(), this, y, m, d);
        }

        public void onDateSet(DatePicker view, int year, int month, int day) {
            int mon = month +1;
            date_time = day + "/" + mon + "/" + year;

            sp.edit().putString("year", String.valueOf(year)).commit();
            sp.edit().putString("month", String.valueOf(month)).commit();
            sp.edit().putString("day", String.valueOf(day)).commit();

            TimePickerFragment fragment2 = new TimePickerFragment();
            fragment2.show(getActivity().getSupportFragmentManager(), "tp");
        }
    }

    public static class TimePickerFragment extends DialogFragment implements TimePickerDialog.OnTimeSetListener {
        @Override
        public Dialog onCreateDialog(Bundle savedInstanceState) {
            int h, min = 0;
            now = Calendar.getInstance();
            if (sp.getString("hour", ""). equals("")){
                h = now.get(Calendar.HOUR_OF_DAY);
            } else {
                h = (int)Double.parseDouble(sp.getString("hour", ""));
            }
            if (sp.getString("min", ""). equals("")){
                min = now.get(Calendar.MINUTE);
            } else {
                min = (int)Double.parseDouble(sp.getString("min", ""));
            }

            return new TimePickerDialog(getActivity(), this, h, min, DateFormat.is24HourFormat(getActivity()));
        }

        public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
            sp.edit().putString("hour", String.valueOf(hourOfDay)).commit();
            sp.edit().putString("min", String.valueOf(minute)).commit();

            date_time = date_time + ", " + hourOfDay + ":" + minute;

            TextView textview1 = getActivity().findViewById(R.id.textView);
            textview1.setText(date_time);
        }
    }

}