Thread: How to sort this?

Originally Posted by Purple01

...So arrayList is full of these string1 things.
Now start and end are both number.

Is there a way that i can sort the arrayList on the start?
Like that I want 1-4 before 3-2?

One way would be to create a custom comparator and use Collections.sort. It could go like this:

    class CustomComparator implements Comparator<String>
    {
        @Override
        public int compare(String str1, String str2)
        {
              //Code that extracts the integer values of substrings of str1 and str2
              // Call them int1 and int2
              // Return int1-int2
        }

Then, call the Collections.sort function with your ArrayList<String> object like this:

        ArrayList<String> al = new ArrayList();
 
      //
      // Code to populate al goes here
      //
 
        System.out.println("Original: ");
        for (String str : al) {
            System.out.println("  " + str);
        }
 
        // For amusement, just sort by comparing strings
        Collections.sort(al);
        System.out.println("Natural sort of the Strings: ");
        for (String str : al) {
            System.out.println("  " + str);
        }
 
        // The real goal: Sort by numeric value of the first item in the "num1-num2" Strings
        Collections.sort(al, new CustomComparator());
        System.out.println("CustomComparator sort of the Strings: ");
        for (String str : al) {
            System.out.println("  " + str);
        }

Example output

Original: 
  1-10
  21-18
  25-4
  25-12
  1-9
  17-12
  10-16
  2-4
  17-13
  2-15
Natural sort of the Strings: 
  1-10
  1-9
  10-16
  17-12
  17-13
  2-15
  2-4
  21-18
  25-12
  25-4
CustomComparator sort of the Strings: 
  1-10
  1-9
  2-15
  2-4
  10-16
  17-12
  17-13
  21-18
  25-12
  25-4

Cheers!

Z