Question

Doing homework and I’m stuck.

Let’s say I have an array colors:

["blue", "orange", "green", "black", "red" ]

and these colors occur in a text. When the color occurs there is another array that stores the line number in another array (position array).

[17,4,5,8,8]

Now I want to print by ascending line occurrence so the output would be:

orange
green
black
red
blue

I use the Arrays.sort() to sort the position array.
I believe that this should be done using position.

For example, for printing orange, there is a relation of the sorted array with the position of the color on the array colors.

Can you point me in some direction?

As I started to learn java this as to be done the simplest way possible.

Answer 1

1. You need to associate the indices with each other. I would recommend you to do it in a class (maybe a Pair class with the attributes String color and int line).

   class Pair {
       public String color;
       public int line;
       public Pair(String color, int line) {
           this.color = color;
           this.line  = line;
       }
   }
   

2. Build up an array (or List<Pair>) of the paired objects.

   String[] colors = new String[] {"blue", "orange", "green", "black", "red"};
   int[] lines     = new int[]    {    17,        4,       5,       8,     8};
   
   List<Pair> pairs = new LinkedList<Pair>();
   for (int i = 0; i < colors.length; i++)
       pairs.add(new Pair(colors[i], lines[i]));
   

3. Sort the array of Pairs with an Comparator using Arrays.sort (or Collection.sort) method depending on your line attribute.

   Collections.sort(pairs, new Comparator<Pair>() {
       public int compare(Pair p1, Pair p2) {
           return Integer.valueOf(p2.line).compareTo(p1.line);
       }
   });
   

   Another option would be to implement Comparable<Pair> in Pair.

4. Print the array using a loop