Usually, when we deal with databases, we don’t face such kind of situation because we query database to get result-set in required order.<\/p>\n
But let’s say you have a List of objects that you want to sort on the basis of two fields. Let’s discuss it with an example.<\/p>\n
I have a list of Tasks (with date and priority fields). I want to sort these tasks ordered by Date and priority-wise (as second level sorting).<\/p>\n
Here, I am going to use Expando class, so I can directly run this in my groovyConsole. But definitely, you can use some ‘Task’ class.<\/p>\n
[groovy]
\nExpando a = new Expando(date: Date.parse(‘yyyy-MM-dd’,’2011-01-01′), priority:1)
\nExpando b = new Expando(date: Date.parse(‘yyyy-MM-dd’,’2011-01-01′), priority:2)
\nExpando c = new Expando(date: Date.parse(‘yyyy-MM-dd’,’2011-01-02′), priority:1)
\nExpando d = new Expando(date: Date.parse(‘yyyy-MM-dd’,’2011-01-01′), priority:3)<\/p>\n
def list = [a,d,c,b]
\n[\/groovy]<\/p>\n
If sorting was required on the basis of date only, it was very simple.<\/p>\n
[groovy]
\nlist.sort(it.date)
\n[\/groovy]<\/p>\n
But as per our requirements – order by date (first level sorting) and priority (second level sorting). We can do something like following.<\/p>\n
[groovy]
\nlist.sort{x,y->
\n if(x.date == y.date){
\n x.priority <=> y.priority
\n }else{
\n x.date <=> y.date
\n }
\n}
\n[\/groovy]<\/p>\n
Well, there could be some better way. If you know please put your comments. But it worked well in my case.<\/p>\n