Trying to sort an array of objects alphabetically but Object can't be converted to String

Question

I am creating a hotel program which has an array filled with objects (Room), and each Room is filled with a customer name. I used an exchange sort to sort the array alphabetically, however I keep getting an error that Room cannot be converted into a String. I am fairly new to Java and I am struggling to find a fix to this. This is my sort below. How could I overcome this issue?

private static void orderedView(Room hotelRef[]) {
    for (int i = 0; i < hotelRef.length; i++) {
        for (int j = i + 1; j < 12; j++) {

            if (hotelRef[i].compareTo(hotelRef[j]) > 0) {
                String temp;
                temp = hotelRef[i];
                hotelRef[i] = hotelRef[j];
                hotelRef[j]= temp;
            }
        }
    }
    System.out.print("Names in Sorted Order:");
    for (int i = 0; i < hotelRef.length - 1; i++) {
        System.out.println(hotelRef[i] + " ");

    }
    System.out.print(hotelRef[12 - 1]);

}

temp is a Room not a string this line of code is bad. String temp;. I would code. Room mRoomTemp; So I know the class by looking at the variable. — danny117
– danny117, Commented Mar 7, 2018 at 21:02

Juan Carlos Mendoza · Accepted Answer · 2018-03-07 21:48:27Z

1

There are some problems here:

if (hotelRef[i].compareTo(hotelRef[j]) this will work if Room implements Comparable (or you have a custom Room.compareTo) that actually compares by customer name. If not then maybe you need:

if(hotelRef[i].getCustomerName().compareTo(hotelRef[j].getCustomerName()) > 0)
temp = hotelRef[i];: temp is a String variable and you are trying to assing a Room to it. Change String temp; to Room temp;

If you are on Java-8 or above then you can sort it simpler using Arrays.sort and Comparator.comparing:

Arrays.sort(hotelRef, Comparator.comparing(Room::getCustomerName));
// or whatever the customer name's getter method is named

edited Mar 7, 2018 at 21:48

answered Mar 7, 2018 at 21:20

Juan Carlos Mendoza

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Steven Gibson · Accepted Answer · 2018-03-07 21:05:37Z

0

When coding Object Oriented Java, you need to create Getters and Setters for retrieving or modifying variables within an object. For example, you would make a function in Room similar to the following:

public String getCustomerName() { return customerName; }

When you call this function on your object, it will return the customer name for you. I hope this helps, and good luck in your future excursions into Object Oriented Java.

answered Mar 7, 2018 at 21:05

Steven Gibson

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Zabuzard · Accepted Answer · 2018-03-07 21:09:20Z

0

Use sort with the Comparator

for example:

Arrays.sort(arr, 0, arr.lenght, (Room lsh, Room rhs) -> {
   return lsh.getName().compareTo(rhs.getName());
});

edited Mar 7, 2018 at 21:09

Zabuzard

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answered Mar 7, 2018 at 21:04

Victor Gubin

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1 Comment

Zabuzard Over a year ago

Note that you can get the same comparator with less code: Comparator.comparing(Room::getName), that's all.

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