Sort a Collection list with two numeric parts of string in Java

Question

Could any one suggest idea to sort the list accordingly : suppose the List contains :

-SP001 of 2017
-SP002 of 2015
-SP001 of 2015
-SP001 of 2016
-SP005 of 2015
-SP003 of 2015

The the out put should be (List must contain in the below order) :

-SP001 of 2015
-SP002 of 2015
-SP003 of 2015
-SP005 of 2015
-SP001 of 2016
-SP001 of 2017

here i need to sort according to number part as well as year part. I have tried collection sort but it gives out put like :

[SP001 of 2015, SP001 of 2016, SP001 of 2017, SP002 of 2015, SP003 of 2015, SP005 of 2015]

write a `Comperator` that does extract the numbers and sorts them according to it. — SomeJavaGuy, Mar 16 '16 at 06:44
Possible duplicate of [How to compare objects by multiple fields](http://stackoverflow.com/questions/369512/how-to-compare-objects-by-multiple-fields) — Yassin Hajaj, Mar 16 '16 at 06:45
Or better: parse the strings upfront to objects with two integers, and sort those objects. — JB Nizet, Mar 16 '16 at 06:45
@Justin Are you aware you can accept answer which solves your problem? — user3437460, Mar 16 '16 at 06:52
@Justin You can click on the `tick` beside the answer which helps you best. You get will 2 pts in return. — user3437460, Mar 16 '16 at 08:37

Bahramdun Adil · Accepted Answer · 2016-03-16T09:13:30.673

0

You can try this: First split the strings and then compare the third element of array.

List<String> list = new ArrayList<>();
list.add("-SP005 of 2015");
list.add("-SP001 of 2017");
list.add("-SP003 of 2015");
list.add("-SP001 of 2015");
list.add("-SP001 of 2016");
list.add("-SP002 of 2015");

Collections.sort(list, new Comparator<String>() {
    public int compare(String o1, String o2) {
        int result = o1.split(" ")[2].compareTo(o2.split(" ")[2]);
        if (result == 0) {// if the years are the same, then compare with first element
            return o1.split(" ")[0].compareTo(o2.split(" ")[0]);
        }
        return result;
    }
});

System.out.println("list = " + list);

And it is the result:

list = [
-SP001 of 2015, 
-SP002 of 2015, 
-SP003 of 2015, 
-SP005 of 2015, 
-SP001 of 2016, 
-SP001 of 2017
]

edited Mar 16 '16 at 09:13

answered Mar 16 '16 at 06:51

Bahramdun Adil

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I am getting Lambda expressions are allowed only at source level 1.8 or above, I am getting this coz am using jdk 7 – Justin Mar 16 '16 at 08:29
Thanks, but i have already tried the above, thats not give me exact answer..List list = new ArrayList<>(); list.add("-SP001 of 2017"); list.add("-SP002 of 2015"); list.add("-SP001 of 2016"); list.add("-SP005 of 2015"); list.add("-SP003 of 2015"); – Justin Mar 16 '16 at 08:48
What do you mean by 'not give me exact answer' the result I got from the code I already posted in the answer, it must work. – Bahramdun Adil Mar 16 '16 at 08:51
sp01 of 2015,sp02 of 2015,sp01 of 2016,sp03 of 2016,sp01 of 2017, this is the example order i needed, thanks for your answers. – Justin Mar 16 '16 at 08:54
OK, then the output is exactly what you want, if you see the answer, it is ordered by year, in ascending order. – Bahramdun Adil Mar 16 '16 at 08:59
yes, but for me sorting must not be with year alone... if sp001 of 2015 means need to sort according to 001 and 2015. in your answer 003 is after 005. – Justin Mar 16 '16 at 09:02
The answer has been updated again, now it is what you were looking for. Good Luck! – Bahramdun Adil Mar 16 '16 at 09:14

Yassin Hajaj · Answer 2 · 2016-03-16T09:00:35.040

0

For java-8

You may use two Comparator<String> and the method thenComparing within the Collections#sort method

The first comparator will compare the years, while the second will compare the second String and so directly the first part of each one.

Comparator<String> comp1 = (x, y) -> x.split(" ")[2].compareTo(y.split(" ")[2]);
Comparator<String> comp2 = (x, y) -> x.compareTo(y);

Collections.sort(list, comp1.thenComparing(comp2));

System.out.println(list);

Output

[SP001 of 2015, SP002 of 2015, SP003 of 2015, SP005 of 2015, SP001 of 2016, SP001 of 2017]

edited Mar 16 '16 at 09:00

answered Mar 16 '16 at 06:55

Yassin Hajaj

21,337
9
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:Lambda expressions are allowed only at source level 1.8 or above, I am getting this coz am using jdk 7 – Justin Mar 16 '16 at 08:28
@Justin Ok, I'm letting my answer though in case someone might need it or if you upgrade to jdk 8 – Yassin Hajaj Mar 16 '16 at 09:00

Sort a Collection list with two numeric parts of string in Java

2 Answers2

For java-8

Output

Linked