Java sort HashMap values which are List<Value>

Question

I got the HashMap:

HashMap<String, List<Value>> facetsInCategories = new HashMap<>();

I need to sort the List of Values inside the value of this HashMap. The value in the list has four fields, and I need to sort the list by the "translatedValue" String. That is why I put "getTranslatedValue" in custom comparator. Here is Value object fields:

public String name;
public int count;
private String translatedValue;
private String translation;

And here is what I tried:

for (List<Value> value : facetsInCategories.values()) {
    Collections.sort(value, new Comparator<Value>() {
            @Override
            public int compare(Value o1, Value o2) {
                return o1.getTranslatedValue().compareTo(o2.getTranslatedValue());
            }
    });
}

I've been doing this for couple of hours now, so I thought you may advise somehow on that.

What is the result you are getting and what is the result you are expecting? — RealSkeptic
– RealSkeptic, Commented Oct 16, 2014 at 12:11
I would expect above code to sort your Value-objects according to the result of String-compareTo of their 'translatedValue'... is this happening already? — JBA
– JBA, Commented Oct 16, 2014 at 12:13
Why do you put the list back on the Map? there is no need for that. Sorting should work file. — A4L
– A4L, Commented Oct 16, 2014 at 12:13
what I am worried about right now is that for (List<Value> value : facetsInCategories.values()) throws an error on the second iteration. This should not happen in my opinion. — TheKolaNN
– TheKolaNN, Commented Oct 16, 2014 at 12:21
facetsInCategories.put("test", value); was just for tests, I deleted it from the question right now. — TheKolaNN
– TheKolaNN, Commented Oct 16, 2014 at 12:22

Teddy · Accepted Answer · 2014-10-16 12:14:07Z

1

Code looks fine. Collections.sort will sort the lists in place.

Why do you need this line?

facetsInCategories.put("test", value);

The lists are already added in the hashmap. And they will be sorted where they are.

From null-safety point of view, you are assuming this will never be null:

o1.getTranslatedValue()

answered Oct 16, 2014 at 12:14

Teddy

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SMA · Accepted Answer · 2014-10-16 12:20:09Z

0

Comment this line and it should do the trick:

facetsInCategories.put("test", value);

answered Oct 16, 2014 at 12:20

SMA

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1 Comment

TheKolaNN Over a year ago

facetsInCategories.put("test", value); was just for tests, I deleted it from the question right now. What I am worried about right now is that for (List<Value> value : facetsInCategories.values()) throws an error on the second iteration. This should not happen in my opinion.

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