How can I sort this ArrayList the way that I want?

Question

Here is a simple sorting program of an ArrayList:

ArrayList<String> list = new ArrayList<String>();  list.add("1_Update"); list.add("11_Add"); list.add("12_Delete"); list.add("2_Create");  Collections.sort(list); for (String str : list) {   System.out.println(str.toString()); } 

I was expecting the output of this program as:

1_Update 2_Create 11_Add 12_Delete 

But when I run this program I am getting output as:

11_Add 12_Delete 1_Update 2_Create 

Why is this and how do I get the ArrayList to sort as shown in the expected output?

Answer 1

You could write a custom comparator:

Collections.sort(list, new Comparator<String>() {     public int compare(String a, String b) {         return Integer.signum(fixString(a) - fixString(b));     }     private int fixString(String in) {         return Integer.parseInt(in.substring(0, in.indexOf('_')));     } });