Sorting Vector in Ascending order and saving to a text file

Question

I have a Vector that needs to be sorted in Ascending order, as im still a beginner im finding slightly hard to make this work, I've been trying to do it with insertElementAt and compareTo, but I didnt manage. Can anyone Help?

Answer 1

You should decide a criteria based on what you are sorting your vector. You can't just compare two objects, you should pick a "price" or "code", etc. and compare your objects based on that value

Answer 2

There are two approaches you can take:

1. Make your Product class implement the Comparable interface. This way, you can implement the compareTo method which is the base for the sorting operation. This method defines ordering, because it determines which element is higher and which one is lower by returning a positive int, zero or a negative int.

2. Implement your very own Comparator. A comparator defines a comparation method that takes two elements as a base and compares them in the same way that compareTo does. The advantage here is that you can switch ordering criteria by ordering with a different Comparator.

Finally, the sorting can be performed by the use of any of the overloads of Collections#sort that takes your collection as an argument and a Comparator if you decide to use one.

Answer 3

To make the Product class Sortable according to code . You can implement Comparable interface to your Product class and override compareTo method. Your Product class would look like this then:

import java.util.*;
class Product implements Comparable<Product>
{
    String desc, code, phrase;
    double price;

    public Product()
    {
        this.desc = "";
        this.code = ""; // later on irid jinbidel
        this. price = 0.0; 
        this.phrase = "";   
    }
    public Product(String desc, String code, String phrase, double price){
        this.desc = desc;
        this.code = code; // later on irid jinbidel
        this. price = price; 
        this.phrase = phrase;
    }
    @Override
    public String toString(){
        return code;//+", "+desc+", "+price+", "+phrase+".";

    }
    @Override
    public int compareTo(final Product obj) {
        return code.compareTo(obj.code);
    }
}

To Test if it is sorting Correctly here is simple Demo:

public class TestProduct
{
    public static void main(String[] st)
    {
        Vector<Product> v = new Vector<Product>();
        for (int i = 9 ; i > 0 ; i-- )
        {
            v.add(new Product("MyProduct",i+"Product","Good Product",34.5));
        }
        System.out.println("Before sorting");//Records inserted in decreasing order of code.
        System.out.println(v);
        Collections.sort(v);
        System.out.println("After sorting");//Records showing in increasing order of code.
        System.out.println(v);
    }
}