为什么.equals（）不起作用？

Question

I'm working in Eclipse (Android). In the following blocks, EmployeeInt and RestaurantInt are data types and query() opens a connection to the database and parses the results. When I print the query results, I get identical strings, but the boolean is still false. I've tried trimming the strings, but that didn't help.

public boolean verifyEmployee(String email, String password) {
    ArrayList<EmployeeInt> employeeEmailID = query("SELECT employeeID FROM employees WHERE emailAddress = \'"+email+"\'");
    ArrayList<EmployeeInt> employeePasswordID = query("SELECT employeeID FROM employees WHERE password = \'"+password+"\'");
    String stringEmployeeEmailID = employeeEmailID.toString();
    String stringEmployeePasswordID = employeePasswordID.toString();

    if(stringEmployeeEmailID.equals(stringEmployeePasswordID)) {
        return true;
    } else {
        return false;
    }
}

Executing the above gives me false, while executing the following block (virtually identical) gives me true.

public boolean verifyRestaurant(String email, String password) {
    ArrayList<RestaurantInt> restaurantEmailID = query("SELECT restaurantID FROM restaurants WHERE emailAddress = \'"+email+"\'");
    ArrayList<RestaurantInt> restaurantPasswordID = query("SELECT restaurantID FROM restaurants WHERE password = \'"+password+"\'");
    String stringRestaurantEmailID = restaurantEmailID.toString();
    String stringRestaurantPasswordID = restaurantPasswordID.toString();

    if(stringRestaurantEmailID.equals(stringRestaurantPasswordID)) {
        return true;
    } else {
        return false;
    }
}

Can anyone point out my mistake?

EDIT

I changed it to this and it worked:

public boolean verifyEmployee(String email, String password) {
    ArrayList<EmployeeInt> employeeEmailID = query("SELECT * FROM employees WHERE emailAddress = \'"+email+"\'");
    ArrayList<EmployeeInt> employeePasswordID = query("SELECT * FROM employees WHERE password = \'"+password+"\'");
    int intEmployeeEmailID = employeeEmailID.get(0).getID();
    int intEmployeePasswordID = employeePasswordID.get(0).getID();

    if(intEmployeeEmailID==intEmployeePasswordID) {
        return true;
    } else {
        return false;
    }
}

I know I could also use return (condition), but I would like to add some messages if the login fails, something like:

System.err.println("email address and password do not correspond");

I'm not making an app to publish, it's merely for an assignment. Thanks for the help!

Answer 1

You are calling toString() on an ArrayList . Two different ArrayList objects will return two different toString() strings. You probably meant to get the first element of the ArrayList, and convert THAT to a string.

Example

EmployeeInt is your custom object. In my example, I assume it has some int field that can be retreived with getID() .

ArrayList<EmployeeInt> idList = query("SELECT employeeID FROM employees WHERE emailAddress = \'"+email+"\'");
int ID = idList.get(0).getID();
stringEmployeeEmailID = String.valueOf(ID);

This may be easier to read than code:

• query() returns an ArrayList
• We extract the first element of the ArrayList - this is the part you left out
• We get the ID of that element
• We convert it to a String