Cannot insert data into sqlite database in android

This question has been answered many time but still unable to find my mistake. Am creating a database and a table to insert some value into SQLite database. but it shows SQLite Exception.

This is my code that i have tried.

Main activity:

when i click Register button it should create the database, table and then enter the data into table.

private static final int DATABASE_VERSION = 2;
private static final String DATABASE_NAME = "userDB";
private static final String TABLE_USER = "users";

private static final String KEY_ID = "id";
private static final String KEY_USERNAME = "username";
private static final String KEY_PASSWORD = "password";

db = new DataBaseHandler(RegisterActivity.this); // my database handler

    username = (EditText) findViewById(R.id.usernameRegister);
    password = (EditText) findViewById(R.id.passwordRegister);
    registerSave = (Button) findViewById(R.id.saveRegister);

    registerSave.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub

            usernameInput = username.getText().toString();
            passwordInput = password.getText().toString();

            //createDB();
            Log.d("Insert: ", "Inserting ..");
            db.addUsers(new Users(""+usernameInput,""+passwordInput));
        //  db.addUsers(new Users("password",passwordInput));

            Log.d("inserted", ""+db);

            Log.d("inputs", "" + usernameInput + ":" + passwordInput);

        }
    });

This is my Database Handler class

public DataBaseHandler(Context context) {

    super(context, DATABASE_NAME, null, DATABASE_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
    // TODO Auto-generated method stub
    String CREATE_USER_TABLE = "CREATE TABLE IF NOT EXISTS "+TABLE_USER+" (" + KEY_ID
            + "INTEGER PRIMARY KEY AUTOINCREMENT," + KEY_USERNAME + " TEXT,"
            + KEY_PASSWORD + " TEXT" + ")";
    db.execSQL(CREATE_USER_TABLE);
    Log.d("sqlite DB:","Created"+db.toString());

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // TODO Auto-generated method stub
    db.execSQL("DROP TABLE IF EXISTS "+ TABLE_USER);
    onCreate(db);
}

// Adding new contact
void addUsers(Users users) {
    SQLiteDatabase db = this.getWritableDatabase();

    ContentValues values = new ContentValues();
    values.put(KEY_USERNAME, users.getUsername()); // User Name
    values.put(KEY_PASSWORD, users.getPassword()); // Password

    // Inserting Row
    db.insert(TABLE_USER, null, values);
    db.close(); // Closing database connection
}

Users getUser(int id) {
    SQLiteDatabase db = this.getReadableDatabase();

    Cursor cursor = db.query(TABLE_USER, new String[] { KEY_ID,
            KEY_USERNAME, KEY_PASSWORD }, KEY_ID + "=?",
            new String[] { String.valueOf(id) }, null, null, null, null);
    if (cursor != null)
        cursor.moveToFirst();

    Users users = new Users(Integer.parseInt(cursor.getString(0)),
            cursor.getString(1), cursor.getString(2));
    // return contact
    return users;
}

and this is userclass to get the user data.

public class Users {

int _id;
String _username;
String _password;

public Users() {

}

public Users(int id, String username, String password) {
    this._id = id;
    this._username = username;
    this._password = password;
}

public Users(String username, String password) {
    this._username = username;
    this._password = password;
}

public int getId() {
    return this._id;
}

public void setId(int id) {
    this._id = id;
}

public String getUsername() {
    return this._username;
}

public void setUsername(String username) {
    this._username = username;
}

public String getPassword() {
    return this._password;
}

public void setPassword(String password) {
    this._password = password;
}

}

am also posting the logcat of the output:

Logcat:

01-07 07:38:19.613: E/SQLiteDatabase(3467): Error inserting username=sagar password=asdfg
01-07 07:38:19.613: E/SQLiteDatabase(3467): android.database.sqlite.SQLiteException: no such table: users (code 1): , while compiling: INSERT INTO users(username,password) VALUES (?,?)
01-07 07:38:19.613: E/SQLiteDatabase(3467):     at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
`

Am struck. need some help.