无法弄清楚为什么对象的 ArrayList 没有正确排序

Question

I'm working on an exchange sort for an ArrayList of objects so that it can be sorted ascending depending on the value in the object. When I compile it, everything works great until the last element is not sorted properly. I suspect that the problem is with the iterator. I tried many combinations but it won't sort properly. Also, I can't use sort() or any prebuilt libraries. I'd appreciate any guidance!

void sortAndDisplay (ArrayList<Car> cars) {

    Car temp;

    for (int i = 0; i < cars.size() -1; i++) {
        for (int j = i+1; j < cars.size(); j++ ) {
            if (((cars.get(i).getMake()).compareToIgnoreCase(cars.get(j).getMake()) > 0)) {
                temp = cars.get(i);
                cars.set(i, cars.get(j));
                cars.set(j, temp);
            }


        }
    }


      for (int i = 0; i < cars.size(); i++) { 
          System.out.print(cars.get(i)+"\n\n");

      }


}

The Car class:

public class Car {
String make;
String model;


public Car (String make,
            String model)   {

    this.make = make;
    this.model = model;

}

public String getMake() {
    return make;

}

The method I used to read the values from the file:

ArrayList<Car> readCars(FileReader file) throws Exception  {
    String arr[] = {};
    String line = "";
    BufferedReader scan = new BufferedReader(file);
    ArrayList<Car> carsArr = new ArrayList<Car>();

    while ((line = scan.readLine()) != null) {
        arr = line.split(","); 
        Car car = new Car(arr[0], arr[1]);
        carsArr.add(car);
    }
    System.out.println("The file was read.");
    return carsArr;

}

Answer 1

java has sorting built in:

void sortAndDisplay (List<Car> cars) {
    cars.sort(Comparator.comparing(Car::getMake));
    System.out.println(cars.stream().collect(Collectors.joining("\n\n")));
}

Answer 2

I created the file x.txt with the following data:

WERTfgd, bmw
ETRHFDdfgsdf, bmw
ewrd, bmw
HTfgdfgs, bmw
dDSFSfgd, bmw
ter, bmw
jhvbn, bmw
Frqw, bmw

I copied your code literally by adding getMake() into this System.out.print (cars.get (i).getMake () + "\ n \ n");in order to get the wanted output...

Output

dDSFSfgd

ETRHFDdfgsdf

ewrd

Frqw

HTfgdfgs

jhvbn

ter

WERTfgd

Which is correct, so I can't figure out what's your problem.

Maybe you are not sure how the method compareToIgnoreCase() works?

Answer 3

Tried your code with short example list and it worked. Could you give a failing example input with corresponding output?

BTW I recommend adding a toString() method to the Car class. For example:

@Override
public String toString() {
    return "<Car<" + make + "><" + model + ">>";
}

With that printing the list of cars can be done like:

System.out.println(cars);