how to access data from sqlite database?

I am trying to access data stored in sqlite database.I am trying to access data using Cursor.I have written function getInformation() to access data.My problem is when I am trying to call this function it throws java.lang.NullPointerException error.I am not getting any idea why it do so.Can someone please help me out with this error.

E/AndroidRuntime: FATAL EXCEPTION: main Process: com.edkul.vimal.edkul, PID: 2006 java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.Cursor com.edkul.vimal.edkul.DatabaseHandler.getInformation(com.edkul.vimal.edkul.DatabaseHandler)' on a null object reference

Here is my function to get data from Db:
<pre><code>
    public Cursor getInformation(DatabaseHandler db){
    SQLiteDatabase sq = db.getWritableDatabase();
    String[] columnNames ={"StudentName","StudentEmail","StudentPassword",        
    "StudentConfirmPassword","InstituteName","ContactInfo"};
    String tableName = "StudentRecords";
    Cursor cr = sq.query(tableName,columnNames,null,null,null,null,null);
    return cr;
    }

</code></pre>

Part of code where I am trying to call this function :
<pre><code>


>      btn = (Button) findViewById(R.id.loginButton);
>         userName = (EditText) findViewById(R.id.userName);
>         passWord = (EditText) findViewById(R.id.passWord);
>         btn.setOnClickListener(new View.OnClickListener() {
>         @Override
>         public void onClick(View view) {
>         String username = userName.getText().toString();
>         String userpass = passWord.getText().toString();
>         boolean login_status = false;
>         Cursor cr1 = dbHandler.getInformation(dbHandler);
>         String name = "";
>         cr1.moveToFirst();                       
>         do {
>         if(username.equals(cr1.getString(0))
>         &&userpass.equals(cr1.getString(2))){
>         login_status = true;
>         name = cr1.getString(0);
>         }
>         }while(cr1.moveToNext());
>         if (login_status){
>         Intent intentMain = new Intent(welcomepage.this,
>         UserProfile.class);
>         startActivity(intentMain);
>         finish();
>         }    }while(cr1.moveToNext());
>         if (login_status){
>         Intent intentMain = new Intent(welcomepage.this,
>         UserProfile.class);
>         startActivity(intentMain);
>         finish();
>         }

</code></pre>