Function and Button Behavior Questions

import androidx.annotation.RequiresApi;
import androidx.appcompat.app.AppCompatActivity;

import android.Manifest;
import android.content.Context;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.Listener;
import android.location.LocationManager;
import android.os.Build;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;

public class MainActivity extensions AppCompatActivity{
    double data1, data2;


    private LocationManager locationManager;

    @RequiresApi(api=Build.VERSION_CODES.M)
    public void onCreate (Bundle savedInstanceState) {
        setContentView(R.layout.activity_main);
        super.onCreate(savedInstanceState);

        locationManager=(LocationManager) this.getSystemService(Context.LOCATION_SERVICE);
        if(checkSelfPermission(Manifest.permission.ACCESS_FINE_LOCATION)!=PackageManager.PERMISSION_GRANTED&&checkSelfPermission(Manifest.permission.ACCESS_COARSE_LOCATION)!=PackageManager.PERMISSION_GRAMITION)
            // TODO:consider calling
            //    Activity# requestPermissions
            // here to request the missing permissions, and then overriding
            //   public void onRequestPermissionsResult(int requestCode, String[]permissions,
            //                                          int[]grantResults)
            // to handle the case where the user grants the permission.See the documentation
            // for Activity# requestPermissions for more details.
            return;
        }
        locationManager.requestLocationUpdate(provider: "gps", minTimeMs: 100, minDistanceM: 0, onLocationUpdate);

    }

    private LocationListener onLocationUpdate=new LocationListener(){

        public void onLocationChanged (Location location) {
            TextView textView1=(TextView) findViewById (R.id.text_view1);
            TextView textView2=(TextView) findViewById (R.id.text_view2);
            // Location.getLatitude(), location.getLongitude() has the latitude and longitude of the current location.
            data1 = location.getLatitude();
            data2 = location.getLongitude();
            String str1 = "Latitude:" + data1;
            textView1.setText(str1);

            // display of longitude
            String str2 = "Longtude:" + data2;
            textView2.setText(str2);
            // Log.d("debug", "checkSelfPermission true";
        }
        public void onProviderDisabled (String provider) {
        }
        public void onProviderEnabled (String provider) {
        }
        public void onStatusChanged(String provider, int status, Bundle extras) {
        }
    };

// I don't know from here at all ↓
    public void onButtonClick (View view) {
        switch(view.getId()) {
            case R.id.button1:
                while(1){
                    
                }
                break;
        }
    }

    public void onButtonClick (View view) {
        switch(view.getId()) {
            case R.id.button2:
                System.out.println(new Date()+distance+"m");
                break;
        }
    }

}