Android Studio : cannot be applied into given types

I'm currently trying to learn SQLite in Android, and followed some tutorials on the internet.
Now I'm stuck with this one error, and I hope someone would point out my mistakes. I'm not sure what caused this problem, I've read most of these threads with the same question as me, but I still can't figure out how to fix it.

Here's the MainActivity.java

package com.nyonyo.sqlitetest;

import android.app.AlertDialog;
import android.content.Context;
import android.database.Cursor;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    DatabaseHelper myDB;
    EditText firstname, lastname, marks, id;
    Button btnAdd;
    Button btnDel;
    Button btnView;
    Button btnUpdate;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        myDB = new DatabaseHelper();

        firstname = (EditText) findViewById(R.id.editFirstName);
        lastname = (EditText) findViewById(R.id.editLastName);
        marks = (EditText)  findViewById(R.id.editMarks);
        id = (EditText) findViewById(R.id.edit_id);

        btnAdd = (Button) findViewById(R.id.button_add);
        btnDel = (Button) findViewById(R.id.button_delete);
        btnView = (Button) findViewById(R.id.button_viewAll);
        btnUpdate = (Button) findViewById(R.id.button_update);

        addData();
        deleteData();
        viewData();
        updateData();

    }

    private void addData() {
        btnAdd.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View view) {
                boolean isInserted = myDB.insertData(firstname.getText().toString(),
                        lastname.getText().toString(),
                        marks.getText().toString());

                if (isInserted)
                    Toast.makeText(MainActivity.this,"Data Inserted", Toast.LENGTH_SHORT).show();
                else
                    Toast.makeText(MainActivity.this,"Insert Data Failed", Toast.LENGTH_SHORT).show();
            }
        });
    }

    private void deleteData() {
        btnDel.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Integer delRow = myDB.deleteData(id.getText().toString());
                if(delRow > 0)
                    Toast.makeText(MainActivity.this,"Row Deleted",Toast.LENGTH_SHORT).show();
                else
                    Toast.makeText(MainActivity.this,"Delete Failed", Toast.LENGTH_SHORT).show();
            }
        });
    }

    private void viewData() {
        btnView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Cursor res = myDB.getData();
                if(res.getCount()==0){
                    showMessage("Error","No Data Found");
                    return;
                }
                StringBuffer buffer = new StringBuffer();
                while(res.moveToNext()){
                    buffer.append("ID :"+ res.getString(0)+"\n");
                    buffer.append("First Name :"+ res.getString(1)+"\n");
                    buffer.append("last Name :"+ res.getString(2)+"\n");
                    buffer.append("Marks :"+ res.getString(3)+"\n\n");
                }
            }
        });
    }

    public void showMessage(String title,String Message){
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setCancelable(true);
        builder.setTitle(title);
        builder.setMessage(Message);
        builder.show();
    }


    private void updateData() {
        boolean isUpdate = myDB.updateData(id.getText().toString(),
                firstname.getText().toString(),
                lastname.getText().toString(),
                marks.getText().toString());

        if(isUpdate)
            Toast.makeText(MainActivity.this,"Database Updated", Toast.LENGTH_SHORT).show();
        else
            Toast.makeText(MainActivity.this,"Update Failed", Toast.LENGTH_SHORT).show();
    }
}

Here's the DatabaseHelper.java

package com.nyonyo.sqlitetest;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

/**
 * Created by NyoNyo on 07/08/2017.
 */

public class DatabaseHelper extends SQLiteOpenHelper {
    public static final String DATABASE_NAME = "Student.db";
    public static final String TABLE_NAME = "Student_table";
    public static final String COL_ID = "ID";
    public static final String COL_FIRSTNAME = "Firstname";
    public static final String COL_LASTNAME = "Lastname";
    public static final String COL_MARKS = "Marks";

    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("Create table" + TABLE_NAME +
                "(ID INTEGER PRIMARY KEY AUTOINCREMENT," +
                "FIRSTNAME TEXT," +
                "LASTNAME TEXT," +
                "MARKS INTEGER)");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXIST" + TABLE_NAME);
        onCreate(db);
    }

    public boolean insertData(String firstname, String lastname, String marks){
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(COL_FIRSTNAME,firstname);
        values.put(COL_LASTNAME,lastname);
        values.put(COL_MARKS,marks);
        long result = db.insert(TABLE_NAME,null,values);
        if(result == -1)
            return false;
        else
            return true;
    }

    public Cursor getData(){
        SQLiteDatabase db = this.getWritableDatabase();
        Cursor res = db.rawQuery("SELECT * FROM"+ TABLE_NAME,null);
        return res;
    }

    public boolean updateData(String id, String firstname, String lastname, String marks){
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(COL_ID, id);
        values.put(COL_FIRSTNAME, firstname);
        values.put(COL_LASTNAME, lastname);
        values.put(COL_MARKS, marks);
        db.update(TABLE_NAME, values, "ID = ?", new String[] {id});
        return true;
    }

    public Integer deleteData(String id){
        SQLiteDatabase db = this.getWritableDatabase();
        return db.delete(TABLE_NAME,"ID = ?", new String[] {id});
    }
}

When I try to run the app, this error shows up.

Error:(28, 16) error: constructor DatabaseHelper in class DatabaseHelper cannot be applied to given types;
required: Context
found: no arguments
reason: actual and formal argument lists differ in length

This is the tutorial I'm following http://www.codebind.com/android-tutorials-and-examples/android-sqlite-tutorial-example/

Thanks in advance.

Is this the Stack Trace ? Not really sure.

08-08 09:50:52.968 22463-22463/? I/art: Late-enabling -Xcheck:jni08-08 09:50:53.429 22463-22463/com.nyonyo.sqlitetest W/System: ClassLoader referenced unknown path: /data/app/com.nyonyo.sqlitetest-1/lib/x8608-08 09:50:53.458 22463-22463/com.nyonyo.sqlitetest I/InstantRun: starting instant run server: is main process08-08 09:50:53.715 22463-22463/com.nyonyo.sqlitetest W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable08-08 09:50:54.018 22463-22463/com.nyonyo.sqlitetest D/AndroidRuntime: Shutting down VM08-08 09:50:54.020 22463-22463/com.nyonyo.sqlitetest E/AndroidRuntime: FATAL EXCEPTION: main                                                                       Process: com.nyonyo.sqlitetest, PID: 22463                                                                       java.lang.RuntimeException: Unable to start activity ComponentInfo{com.nyonyo.sqlitetest/com.nyonyo.sqlitetest.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
                                                                           at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2684)
                                                                           at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2751)
                                                                           at android.app.ActivityThread.-wrap12(ActivityThread.java)
                                                                           at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1496)
                                                                           at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                           at android.os.Looper.loop(Looper.java:154)
                                                                           at android.app.ActivityThread.main(ActivityThread.java:6186)
                                                                           at java.lang.reflect.Method.invoke(Native Method)
                                                                           at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:889)
                                                                           at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:779)
                                                                        Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
                                                                           at com.nyonyo.sqlitetest.MainActivity.addData(MainActivity.java:48)
                                                                           at com.nyonyo.sqlitetest.MainActivity.onCreate(MainActivity.java:40)
                                                                           at android.app.Activity.performCreate(Activity.java:6684)
                                                                           at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
                                                                           at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2637)
                                                                           at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2751) 
                                                                           at android.app.ActivityThread.-wrap12(ActivityThread.java) 
                                                                           at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1496) 
                                                                           at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                           at android.os.Looper.loop(Looper.java:154) 
                                                                           at android.app.ActivityThread.main(ActivityThread.java:6186) 
                                                                           at java.lang.reflect.Method.invoke(Native Method) 
                                                                           at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:889) 
                                                                           at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:779) 08-08 09:50:54.055 22463-22463/com.nyonyo.sqlitetest I/Process: Sending signal. PID: 22463 SIG: 9