在Java中排序对象数组

Question

I'm trying to make a java application that's allows the user to make a catalog for a supermarket, and then display all the products that the user entered to the catalog in ascending order according to the code entered by the user.I have searched for it and found that I can use a method called "sort",but the problem I tried to implement it but it doesn't work with me ,and I don't know where to put it in my code .

The code that I wrote : 2 classes class 1:

public class Catalog {

private String description ; 
private String code ;
private double price ;
private String phrase ;

int counter = 0;

private Catalog [] list = new Catalog [100];

public Catalog (String productDescription , String productCode , double    productPrice  , String productPhrase)
{
    description = productDescription;
    code = productCode;
    price = productPrice;
    phrase = productPhrase;
}

public void setDescription (String productDescription)
{
    description = productDescription;
}

public String getDescription ()
{
    return description;
}

public void setCode (String productCode)
{
    code = productCode;
}

public String getCode ()
{
    return code;
}

public void setPrice (double productPrice)
{
    price = productPrice;
 }

public double getPrice ()
{
    return price;
 }

public void setPhrase (String productPhrase)
{
    phrase = productPhrase;
}

public String getPhrase ()
{
    return phrase;
}

class 2:

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class CatalogTest {
    public static void main(String[] args) throws IOException {
        String name = null;
        String code = null;
        double price = 0.0;
        String phrase = null;
        BufferedReader input = new BufferedReader (new InputStreamReader  (System.in));
        Catalog product = new Catalog(name,code,price,phrase);
        Catalog [] productsArray = new Catalog [100];

        for (int i = 0 ; i < productsArray.length ; i ++)
        {
            System.out.println("Enter product description (or # to stop): ");
            name = input.readLine();
            if (!("#".equals(name)))
            {
                productsArray [i] = product;
                product.setDescription(name);
                System.out.println("Enter product code: ");
                code = input.readLine();
                productsArray [i] = product;
                product.setCode(code);
                System.out.println("Enter product unit price: ");
                price = Double.parseDouble(input.readLine());
                productsArray [i] = product;
                product.setPrice(price);
                System.out.println("Enter product unit phrase: ");
                phrase = input.readLine();
                productsArray [i] = product;
                product.setPhrase(phrase);
                productsArray [i] = new Catalog (name,code,price,phrase);
            }
            else
            {
                System.out.println("Your Catalog:");
                for (int j = 0; j < productsArray.length; j++)
                {
                    if(productsArray[j]!=null)
                    {
                        System.out.printf("%s, %s,$%.2f %s,",
                        productsArray[j].getCode(),
                        productsArray[j].getDescription(),
                        productsArray[j].getPrice(),
                        productsArray[j].getPhrase());
                        System.out.println();
                    }
                }
                break;
            }
        }
    }
}

So any help PLEASE ??

Answer 1

You can write your own Comparator then call the Arrays.sort method:

public static class MyComparator implements Comparator<Catalog> {
    @Override
    public int compare( Catalog first, Catalog second ) {
        return first.getCode().compareTo( second.getCode() );
    }        
}

Arrays.sort( productsArray, new MyComparator() );

Answer 2

Some things first:

private Catalog [] list = new Catalog [100];

Your Catalog class is actualy a single product in the catalog, while the Catalog[] array you instantiate is the catalog itself.

There are many options you can take. I suggest you use a list instead of an array if you can. You can either use Collections#sort and make your Catalog ( Product from now on) class implement the Comparable interface. There, override the compareTo method and do the comparation based on the code.

Other alternative is to use a TreeSet and defining the Comparator that will be used as a base for the sorting. I think you'll be just fine with the first option.

On the other hand, if you have to stick to an array makke use of a Comparator (like with the TreeSet ) and the Arrays#sort method.