java.lang.NullpointExceprion Android develop

Hey guys i am making an android app using Android Studio, but now i have some problems. I want to the user turn to different activity according to its different user type("guest, teacher...etc) but when i write code and run it, Android Studio logcats says "java.lang.NullpointExceprion" in these two class

DBHelper.class

public class DBHelper extends SQLiteOpenHelper{
private final static String DATABASE_NAME = "demo.db";
private final static int DATABASE_VERSION = 1;

private final static String TABLE_NAME = "request_list";
public final static String  ID = "ID";
public final static String NAME = "Name";
public final static String TITLE = "Title";
public final static String DESCRIPTION = "Description";
public final static String DEPARTMENT = "Department";
public final static String CATEGORY = "Category";

private final static String TABLE_NAME0 = "user_info";
private final static String USERID   = "ID";
public final static String USERNAME0 = "Username";
public final static String PASSWORD0 = "Password";
public final static String NAME0 = "Name";
public final static String EMAIL0 = "Email";
public final static String MOBILE0 ="Mobile";
public final static String WRITE   = "Write";
public final static String READ    ="Read";
public final static String VIEW   ="View";
public final static String TYPE     = "Type";


public DBHelper(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
    Log.e("Database operations", "Database created/opened");

}



@Override
public void onCreate(SQLiteDatabase db) {
    String sql_reporter = "CREATE TABLE " + TABLE_NAME0 +
            " (" +  USERID + " INTEGER primary key autoincrement, " +
            ""    + NAME0 + " text, " +
            ""    + EMAIL0 + " text, " +
            ""    + MOBILE0 + " text, " +
            ""    + TYPE  + " text, "+
            ""    + USERNAME0  + " text, "+
            ""    + PASSWORD0  + " text, "+
            ""    + WRITE      + " text, "+
            ""    + READ      + " text, "+
            ""    + VIEW      + " text);";

    db.execSQL(sql_reporter);
    Log.e("Database operations", "Reporter Table created/opened");

    String sql = "CREATE TABLE " + TABLE_NAME +
            " (" + ID     + " INTEGER primary key autoincrement, " +
            ""    + NAME + " text, " +
            ""    + TITLE + " text, " +
            ""    + CATEGORY + " text, " +
            ""    + DEPARTMENT     + " text, " +
            ""    + DESCRIPTION       + " text);";
    db.execSQL(sql);
    Log.e("Database operations", "Require list Table created/opened");


}

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

public Cursor select() {
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor cursor = db
            .query(TABLE_NAME, null, null, null, null, null, null);
    return cursor;
}

public boolean login(String user_name,String password)
{

    SQLiteDatabase sdb=this.getReadableDatabase();
    String sql="select * from user_info where Username=? and Password=?";
    Cursor cursor=sdb.rawQuery(sql, new String[]{user_name, password});
    if(cursor.moveToFirst()==true){
        cursor.close();
        return true;
    }
    return false;

}

public  Cursor getInformation(SQLiteDatabase db)
{
    Cursor cursor;
    String[] projection = {ID,NAME,TITLE,DEPARTMENT,CATEGORY};

    cursor=db.query(TABLE_NAME,projection,null,null,null,null,null,null);
    return  cursor;
}

public Cursor cate(SQLiteDatabase db){
    Cursor cursor;
    String[] projection = {TYPE};
    String selection = "Type=?";

    ***cursor= db.query(TABLE_NAME0,projection,selection,null,null,null,null);***
    return cursor;
}
//‘ˆº”≤Ÿ◊˜

public long UserInfo_insert (String reporter_name,String reporter_email, String reporter_mobile, String user_name,String user_password,String user_type)
{
    SQLiteDatabase db = this.getWritableDatabase();

    ContentValues cv = new ContentValues();

    cv.put(NAME0,reporter_name);
    cv.put(EMAIL0,reporter_email);
    cv.put(MOBILE0,reporter_mobile);
    cv.put(TYPE,user_type);
    cv.put(USERNAME0,user_name);
    cv.put(PASSWORD0,user_password);


    long row = db.insert(TABLE_NAME0, null, cv);
    return row;
}

public long insert(String name,String title,String description,String department, String category)
{
    SQLiteDatabase db = this.getWritableDatabase();

/* ContentValues */ ContentValues cv = new ContentValues();

    cv.put(NAME,name);
    cv.put(TITLE, title);


    cv.put(DEPARTMENT,department);
    cv.put(CATEGORY,category);
    cv.put(DESCRIPTION,description);

    long row = db.insert(TABLE_NAME, null, cv);
    return row;
}
//…æ≥˝≤Ÿ◊˜
public void delete(int id)
{
    SQLiteDatabase db = this.getWritableDatabase();
    String where = ID + " = ?";
    String[] whereValue ={ Integer.toString(id) };
    db.delete(TABLE_NAME, where, whereValue);
}
//–fi∏ƒ≤Ÿ◊˜
public void update(int id, String title,String name,String department, String category,String description)
{
    SQLiteDatabase db = this.getWritableDatabase();
    String where = ID + " = ?";
    String[] whereValue = { Integer.toString(id) };

    ContentValues cv = new ContentValues();
    cv.put(NAME,name);
    cv.put(TITLE, title);
    cv.put(DESCRIPTION,description);

    cv.put(DEPARTMENT,department);
    cv.put(CATEGORY,category);
    db.update(TABLE_NAME, cv, where, whereValue);
}

}

And LoginActivity.class

public class LoginActivity extends Activity implements View.OnClickListener {

private TextView TVToRegister;
private Button submit;

private EditText username;
private EditText code;

private DBHelper demodb;
private Cursor curosr;
private Context mContext;

SQLiteDatabase sqLiteDatabase;

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

    TVToRegister = (TextView) findViewById(R.id.tv_register);
    TVToRegister.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent ToRegister = new Intent(LoginActivity.this,RegisterActivity.class);
            startActivity(ToRegister);
        }
    });

    submit = (Button) findViewById(R.id.btn_submit);
    submit.setOnClickListener(this);

    username = (EditText) findViewById(R.id.edt_username);
    code = (EditText) findViewById(R.id.edt_code);

    demodb= new DBHelper(this);
    sqLiteDatabase = demodb.getReadableDatabase();

}


@Override
public void onClick(View v) {
    String UserName = username.getText().toString();
    String Code     = code.getText().toString();

        if (username.getText().toString().equals("") || code.getText().toString().equals("")) {
            Toast.makeText(getApplicationContext(), "user name and password can not be emprty!", Toast.LENGTH_SHORT).show();
        } else {

            boolean flag = demodb.login(UserName, Code);
            if (flag) {

                ***if (demodb.cate(sqLiteDatabase).getString(3).equals("student"))*** {
                    Intent reporter = new Intent(LoginActivity.this, reporter_new_request.class);
                    startActivity(reporter);
                }
                if (demodb.cate(sqLiteDatabase).getString(3).equals("teacher")) {
                    Intent reparier1 = new Intent(LoginActivity.this, reparier.class);
                    startActivity(reparier1);

                } else {
                    Log.i("TAG", "Joo");
                    Toast.makeText(LoginActivity.this, "JA", Toast.LENGTH_LONG).show();
                    Intent login = new Intent(LoginActivity.this, reporter.class);
                    startActivity(login);
                }
            } else {
                Log.i("TAG", "Ei");
                Toast.makeText(LoginActivity.this, "NEJ", Toast.LENGTH_LONG).show();
            }
        }
    }

}

The wrong code is marked. Could anyone help me?