CODEWITHSUNDEEP
javafor-loopjava-8nested
Tiya
Tiya

Reputation: 563

Java 8 - triple nested for loops

I have written the below code in Java and trying to convert the same to Java 8. The code works as expected for the input (a List created by createTempList method) and output(a map whose key is the 1st decimal of the string and value is the other decimals of the string) 

public static void main(String[] args) {
    List<String> tempList = createTempList();
    createMap8(tempList);
}

public static Map<String,List<String>> createMap8(final List<String> tempList) {
    Map<String,List<String>> vlanFoos = new HashMap<String,List<String>>();
    for(int i=0; i< tempList.size(); i++) {
        String[] idsI = tempList.get(i).split("\\.");
        String vlanI = idsI[0];
        List<String> fooList = new ArrayList<String>();
        for(int j = 0 ; j < tempList.size() ; j ++) {
            String foo = "";
            String[] idsJ = tempList.get(j).split("\\.");
            String vlanJ = idsJ[0];
            if(vlanI.equals(vlanJ)) {
                        for(int k = 1; k < idsJ.length; k++) {
                            foo = foo + idsJ[k];
                            if(idsJ.length - k != 1) {
                                foo = foo + ".";
                            }
                        }
            }
            if(!foo.isEmpty()) {
                fooList.add(foo);
            }
        }
        vlanFoos.put(vlanI, fooList);
    }
    return vlanFoos;
}

Input :

private static List<String> createTempList() {
    List<String> tempList = new ArrayList<String>();
    tempList.add("1.24.75.13.45.91.0");
    tempList.add("1.88.213.110.66.182.127");
    tempList.add("1579.204.45.224.38.12.161");
    tempList.add("1580.204.45.224.38.12.161");
    tempList.add("21.204.45.224.38.12.161");
    tempList.add("39.204.45.224.38.12.161");
    tempList.add("5.12.244.213.2.178.192");
    tempList.add("5.204.45.224.38.12.161");
    tempList.add("5.212.202.109.116.154.217");
    tempList.add("5.212.202.109.116.154.218");
    tempList.add("5.40.153.58.148.24.67");
    tempList.add("5.76.177.205.33.164.80");
    tempList.add("5.84.236.47.13.223.64");
    tempList.add("5.88.213.110.66.182.128");
    return tempList;
}

Output : 

 {1=[24.75.13.45.91.0, 88.213.110.66.182.127], 
 1579=[204.45.224.38.12.161], 
 5=[12.244.213.2.178.192, 204.45.224.38.12.161, 212.202.109.116.154.217, 212.202.109.116.154.218, 40.153.58.148.24.67, 76.177.205.33.164.80, 84.236.47.13.223.64, 88.213.110.66.182.128], 
 39=[204.45.224.38.12.161], 
 1580=[204.45.224.38.12.161], 
 21=[204.45.224.38.12.161]}

Upvotes: 3

Views: 711

Answers (3)

user
user

Reputation: 7604

This is probably the most concise way to do it:

public static Map<String, List<String>> createMap8(final List <String> tempList) {
    return tempList.stream()
                   .map(s -> s.split("\\.", 2))
                   .collect(groupingBy(p -> p[0], mapping(a -> a[1], toList())));
}

For the createTempList method, you can just use Arrays.asList

Upvotes: 2

Sweeper
Sweeper

Reputation: 271625

I suggest you create another class to do the string parsing stuff:

// please give this a better name!
// I don't know what the numbers mean, but you should!
class MyObject {
    private String key;
    private String value;

    public String getKey() {
        return key;
    }

    public String getValue() {
        return value;
    }

    public MyObject(String s) {
        // here I split the string into the first and the rest
        String[] parts = s.split("\\.", 2);
        key = parts[0];
        value = parts[1];
    }
}

Then with streams, the grouping by can be done like this:

public static Map<String,List<String>> createMap8(final List<String> tempList) {

    return tempList.stream().map(MyObject::new).collect(
            Collectors.groupingBy(
                    MyObject::getKey, Collectors.mapping(MyObject::getValue, Collectors.toList())
            )
    );
}

Upvotes: 1

Hadi
Hadi

Reputation: 17289

After modifying your data you can do this: 

Map<String, List<String>> map = tempList.stream()
         .map(t -> t.split("\\.", 2))
         .collect(Collectors.toMap(a -> a[0], v -> new ArrayList<>(singletonList(v[1])),
                                   (l1, l2) -> {l1.addAll(l2); return l1;}
                                  )
                 );

Upvotes: 2

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