Database – Best types of sample projects for software engineering applications

I am a product manager who goes into software development. Since there are a variety of different types of engineers (full stack, front end, back end, etc.), I wondered what the most effective sample projects in my resume would be. My goal is to create 2-3 sample projects that will maximize the number of jobs I qualify for. I'd like to hear recommendations on languages, frameworks, databases, and IDEs to use. Bottom up!

How to transform Excel VBA-based applications into other application types

I have developed an Excel VBA-based set of codes that process a lot of data.
However, what I've seen is that execution time for VBA code continues to increase as the Excel file gets huge (e.g.> 20MB). The execution time is particularly long if the Excel file size is> 100 MB.

I want to know what other server-based application I can use. The prerequisite is that the app / code must be executed without the Internet (in the same lines in which different users access shared folder data).

Note: I am an absolute newcomer and still willing to learn. Sorry if the question is incorrectly framed.

postgresql – Can I use the base / pgsql_tmp directory for non-administrator applications?

I need to export / import JSON files, CSV files, XML, GeoJSON etc. Example:

SELECT pg_catalog.pg_file_write('base/pgsql_tmp/test1_hello.txt', 'Hello World!', false);

All are temporary (exists in a BEGIN / COMMIT) but not a problem?

  1. No risk of file name conflicts? (e.g. my file name and the managed temporary table file name of a pgsql)

  2. no directory risk (base) Volume overflow? (e.g. if I save a large file there)

  3. No risk of reading and writing sequences using the same file name? Will you be in sync in BEGIN / COMMIT sections?


Sometimes we can say that "database servers are not designed for general file I / O" (ref), but sometimes we need them (!) To simplify and automate ETL or interface procedures.

About point 1 and its practical use to simplify export / import procedures (and not to think about where is located data_directory), may be better to create ${data_directory}/base/pgsql_tmp/MyArea as a symbolic connection to another area (e.g. /tmp/MyRealArea).

Applications – What is an ArrayList?

I need to create a set object and save it in an ArrayList and get it from a string resource. I am confused as to what exactly an ArrayList is. I read the documentation on what an ArrayList and what a HashMap is. But when I'm combined, I'm a little confused. I've tried searching ArrayList, but all searches lead me to either ArrayLists or HashMaps only, not both together. Can someone please break this down for me?

Note: This is my first post on Android Stack Overflow. I'm a little confused about how the tags work. I tried adding arraylist, android and hashmap but i think since this page is for android only, are these tags not needed? If there is another tag that I should have added, please update it. Thank you in advance.

android – How to keep audio in the background to use other applications

Hello, I have an app for streaming audio. It works very well when the app is in the foreground. When I leave the app, the audio stops and I want it to be preserved when using other apps. That means the audio stays on. Background Since it is an online station or (Radio Online) and I want users to be able to use other apps while listening, I leave here the code they have so they can check it and they can tell me that it is missing or if it is present error.
Can someone please help me solve this problem?

Main activity code:

public class MainActivity extends AppCompatActivity {

Button play;
AVLoadingIndicatorView progressbar;
MediaPlayer mediaPlayer;
boolean started = false;
boolean prepared = false;
boolean ready=false;

private InterstitialAd mInterstitialAd;
MusicPlayerView mpv;
public static boolean autoplaytrue;
public HeadsetPlugReceiver headsetPlugReceiver;

protected void onCreate(Bundle savedInstanceState) {

    headsetPlugReceiver = new HeadsetPlugReceiver();
    IntentFilter intentFilter = new IntentFilter();
    registerReceiver(headsetPlugReceiver, intentFilter);

    progressbar= findViewById(;

    mpv = findViewById(;

    mediaPlayer = new MediaPlayer();

    mpv.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            if (ready){
                if (started) {
                    started = false;

                } else {
                    started = true;
    new PlayTask().execute(getResources().getString(R.string.streamlink));

public class HeadsetPlugReceiver extends BroadcastReceiver {
    public void onReceive(Context context, Intent intent) {
        if (!Objects.equals(intent.getAction(), Intent.ACTION_HEADSET_PLUG)) {

        boolean connectedHeadphones = (intent.getIntExtra("state", 0) == 1);

        if (!connectedHeadphones){
            if (ready){
                if (started) {
                    started = false;


private class PlayTask extends AsyncTask {

    protected Boolean doInBackground(String... strings) {

        try {
            prepared = true;
        } catch (IOException e) {
        return prepared;

    protected void onPostExecute(Boolean aBoolean) {

protected void onDestroy() {
    if (headsetPlugReceiver != null) {
        headsetPlugReceiver = null;