Sorting text with some rules

Question

I have a arraylist as follows

100 AAA 500-1 Lorem Ipsum
100 BBB 500-2 Lorem Ipsum
101 AAA 500-1 Lorem Ipsum
101 AAA 500-2 Lorem Ipsum
100 BBB 500-3 Lorem Ipsum

I want this to be sorted as

101 AAA 500-1 Lorem Ipsum
101 AAA 500-2 Lorem Ipsum
100 AAA 500-1 Lorem Ipsum
100 BBB 500-2 Lorem Ipsum
100 BBB 500-3 Lorem Ipsum

First, descending by number (101, 100).

Second, ascending by three letter word (AAA, BBB).

Third, ascending by third column (500-1, 500-2, 500-3)

I can split each element by space and get individual word and sort. But can anyone please help me with any other way or known algorithm? Please let me know if you need more information.

Thank you in advance.

Answer 1

Creation of a Comparator will solve your problem. You should implement something like this:

public class MyComparator implements Comparator<MyObject> {    
  public int compare(MyObject o1, MyObject o2) {
    if (o1 == null || o2 == null) {
      throw new NullPointerException();
    }    
    if (o1.getValue1() != o2.getValue1()) {
      return Integer.compare(o1.getValue1(), o2.getValue1());
    }    
    return Integer.compare(o1.getValue2(), o2.getValue2());
  }
}

Of course there are more ways to solve this problem, e.g., you can implement your own sorting algorithm. However, I think that the use of Comparator is the right "java-way" to solve it.

Answer 2

I assume that you have a Collection of String.

I will be using Comparator to solve it.

    List<String> myCollection = new ArrayList<String>();

    Collections.sort(myCollection, new Comparator<String>() {
        @Override
        public int compare(String o1, String o2) {
            // splitting it with space character
            String[] split1 = o1.split(" ");
            String[] split2 = o2.split(" ");

            int i1 = Integer.parseInt(split1[0]);
            int i2 = Integer.parseInt(split2[0]);

            int diff = (i2 - i1);

            if(diff != 0){ // if two integer are equal
                return diff;
            }else{
                return split2[1].compareTo(split1[1]);
            }
        }
    });