Java中字符串数组的数组的数据结构

Question

I checked other questions and googled as well but didn't find a proper answer according to my demand.

This is web app and I am using a rest service. I have a class Request and it has an attribute RequestedAttrbs . User have to send RequestAttrbs and their values in request and i have to store them.

Now user can provide:

id: 123
marks: 12, 13, 14

Problem is user can provide multiple attributes and can provide multiple values for each attribute. Which data structure will be best to handle this? I am new to java and want to solve this problem.

Waiting for your positive reply.

Answer 1

You can just use a normal Map<String, List<String>> type, for example:

String key = "keyValue";
String value1 = "value1";
String value2 = "value2";
String value3 = "value3";

Map<String, List<String>> requestAttrbs1 = new HashMap<String, List<String>>();

if (!requestAttrbs1.containsKey(key)) {
    requestAttrbs1.put(key, new ArrayList<String>());
}
requestAttrbs1.get(key).add(value1);
requestAttrbs1.get(key).add(value2);
requestAttrbs1.get(key).add(value3);

requestAttrbs1.get(key).remove(value2);

for (String value : requestAttrbs1.get(key)) {
    System.out.println(value);
}

Alternatively, if you can use libraries you might want to look at the MultiValueMap in Commons Collections :

MultiValueMap<String, String> requestAttrbs2 = new MultiValueMap<String, String>();

requestAttrbs2.put(key, value1);
requestAttrbs2.put(key, value2);
requestAttrbs2.put(key, value3);

requestAttrbs2.removeMapping(key, value2);

for (String value : requestAttrbs2.getCollection(key)) {
    System.out.println(value);
}

Both code snippets will print out:

value1
value3

As you can see the MultiValueMap version is slightly shorter, saving you the trouble of checking whether the key already exists and explicitly getting the list out yourself.