Compare and sort strings Java

Question

I have array of strings: 15MB,12MB, 1TB,1GB. I want to compare them lexicographically by just following the rule that MB are smaller than GB and TB. So at the end I want to get: 12MB,15MB,1GB,1TB. I found a way to compare the letters:

 final static String ORDER="MGT";

public int compare(String o1, String o2) {
       int pos1 = 0;
       int pos2 = 0;
       for (int i = 0; i < Math.min(o1.length(), o2.length()) && pos1 == pos2; i++) {
          pos1 = ORDER.indexOf(o1.charAt(i));
          pos2 = ORDER.indexOf(o2.charAt(i));
       }

       if (pos1 == pos2 && o1.length() != o2.length()) {
           return o1.length() - o2.length();
       }

       return pos1  - pos2  ;
    }

I'm thinking of splitting the string by numbers and letter but then how can I sort them by their letters "MB.." and then by their numbers. Do I use two comparators or something else?

Answer 1

it will be much easier to compare if you first convert data to a common unit (e.g. MB). if values are same after this conversion then you should apply lexicographical sorting, it may look like this:

private int convertToMegaBytes(String s) {

    char c = s.charAt(s.length() - 2);

    if(c == 'G')
        return 1024 * Integer.parseInt(s.substring(0, s.length() - 2));
    if(c == 'T')
        return 1024 * 1024 * Integer.parseInt(s.substring(0, s.length() - 2));

    return Integer.parseInt(s.substring(0, s.length() - 2));

}

final static String ORDER = "MGT";

public int compare(String o1, String o2) {
    int v = convertToMegaBytes(o1)  - convertToMegaBytes(o2);
    // if values are equal then compare lexicographically
    return v == 0 ? ORDER.indexOf(o1.charAt(o1.length() - 2)) - ORDER.indexOf(o2.charAt(o2.length() - 2)) : v;
}