Android null object reference error [duplicate]

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• What is a Null Pointer Exception, and how do I fix it? 12 answers

I'm trying to receive information from a sqlite database in a class called userLogin (it's just for testing). The database and table already exists. This is my code:

  public class userLogin {

protected SQLiteDatabase db;
protected Cursor c;
protected static final String SELECT_SQL = "SELECT email,password FROM userInformation";
public String email;
Public String password;

        public void userLogin()
        {
            setValues();
        }
        public void setValues() {
            //database values
            c = db.rawQuery(SELECT_SQL, null);
            if ((c.moveToFirst()) || !(c.getCount() == 0)) {
                c.moveToFirst();
                this.email = c.getString(0);
                this.password = c.getString(1);
            }
            else {
                this.email = "empty";
                this.password = "empty";
            }
        }

        public String String()
        {
            return this.email;
        }
    }

I call the class like this:

userLogin checkLogin = new userLogin();
Toast.makeText(Login.this, checkLogin.test(), Toast.LENGTH_SHORT).show();

When I do this I receive the error:

java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.Cursor android.database.sqlite.SQLiteDatabase.rawQuery(java.lang.String, java.lang.String[])' on a null object reference