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Quick way to compare String [] with List

I would like to compare String arrays with a list with market objects.

I implemented the following code:

private List<Data> addMarketData(List<Data> list) {
    String[] SEE = new String[]{"Albania", "Bosnia and Herzegovina", "Bulgaria", "Croatia", "Macedonia FYR", "Moldavia", "Montenegro", "Romania", "Serbia", "Slovenia" };
    List<String> seeList = Arrays.asList(SEE);
    String[] CEE = new String[]{"Czech Republic", "Hungary", "Poland", "Slovakia"}; 
    List<String> ceeList = Arrays.asList(CEE);
    for (int i = 0; i < list.size(); i++) {
        for (int j = 0; j < seeList.size(); j++) {
            if(list.get(i).getPropertyCountry().equals(seeList.get(j).toString())) {
                list.get(i).setMarket("SEE");
            }   
        }
        for (int k = 0; k < ceeList.size(); k++) {
            if(list.get(i).getPropertyCountry().equals(ceeList.get(k).toString())) {
                list.get(i).setMarket("CEE");
            }   
        }
    }
    return list;
}

However, I believe that this code creates more overhead than it really should. Especially for loops. Can I use one loop?

So how to make this piece of code much faster?

I appreciate your answer!

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4 answers

Move all data to Set<String>:

String[] SEE = ...
Set<String> setSEE = new HashSet<>(Arrays.asList(SEE));
String[] CEE = ...
Set<String> setCEE = new HashSet<>(Arrays.asList(CEE));
for (Data data : list) {
    if (setSEE.contains(data.getPropertyCountry()) {
        data.setMarket("SEE");
    } else if (setCEE.contains(data.getPropertyCountry()) {
        data.setMarket("CEE");
    }
}

This will not create an overhead that you might think of. Also, it is faster than your current O (N ^ 2) approach.

, Map<String, String>, @Narmer, , .

Java 7, . Java 5 6 :

Set<String> setSEE = new HashSet<String>(Arrays.asList(SEE));
//...
Set<String> setCEE = new HashSet<String>(Arrays.asList(CEE));
+6

, HashSet<String> . A HashSet<String> O (1) , O (n) . HashMap<String,String> , "SEE" "CEE".

Map<String,String> lut = new HashMap<String,String>();
for(String s : new String[]{"Albania", "Bosnia and Herzegovina", "Bulgaria", "Croatia", "Macedonia FYR", "Moldavia", "Montenegro", "Romania", "Serbia", "Slovenia" }) {
    lut.put(s,"SEE");
}
for(String s : new String[]{"Czech Republic", "Hungary", "Poland", "Slovakia"}) {
    lut.put(s,"CEE");
}

for (Data data : list) {
    data.setMarket(lut.get(data.getPropertyCountry()));
}

HashMap<String,String> ( ) ( ). , , HashMap<String,String> ( 14).

+1

.

private static final Map<String, String> markets = new HashMap<String,String>(){{
    put("Albania", "SEE");
    put("Bosnia and Herzegovina", "SEE");
    ...
    put("Hungary", "CEE");
    ...
}}


for(Data data: list){
    data.setMarket(markets.get(data.getPropertyCountry()));
}

, . , data.getPropertyCountry() ( ) , , :

for(Data data: list){
    if(data.getPropertyCountry()!=null){
        String market = markets.get(data.getPropertyCountry());
        data.setMarket(market==null?"default market":market);
    }
    else data.setMarket("default value"); //if needed
}

Java 8:

for(Data data: list.stream().filter(p -> p.getPropertyCountry() != null).collect(Collectors.toList())){
    String market = markets.get(data.getPropertyCountry());
    data.setMarket(market==null?"default market":market);
}
+1

seeList ceeList HashSet, contains(). HashSet contains() .

Set<String> seeSet = new HashSet<>();
Collections.addAll(seeSet, SEE);

Set<String> ceeSet = new HashSet<>();
Collections.addAll(ceeSet, CEE);

:

for (int i = 0; i < list.size(); i++) {
    if (seeSet.contains(list.get(i).getPropertyCountry()) {
        list.get(i).setMarket("SEE");
    }

    if (ceeSet.contains(list.get(i).getPropertyCountry()) {
        list.get(i).setMarket("CEE");
    }
}
+1

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