Retrieving a key from HashMap based on part of certain strings in the key?

Question

Task: Read a XML file to create a Template;

I am reading this XML file as mentioned below and putting it in a HashMap. to get a Key-Value pair, where Key is value under Element attribute "name" and Value is Element Value. eg: Key: map.abc.color.PRIMARY and Value: #FFFFFF eg: Key: map.abc.node.TEXT1 and Value: value1

<properties>
    <property name="map.abc.color.PRIMARY">#FFFFFF</property>
    <property name="map.abc.color.SECONDARY">#F0F0F0</property>
    <property name="map.abc.node.TEXT1">value1</property>
    <property name="map.abc.node.TEXT2">value2</property>
    <property name="map.abc.node.lowercase">value3</property>   
    <property name="map.abc.strFile">/path/to/file</property>

    <property name="map.pqr.color.PRIMARY">#000000</property>
    <property name="map.pqr.color.SECONDARY">#ABABAB</property>
    <property name="map.pqr.node.WORD1">value4</property>
    <property name="map.pqr.node.WORD2">value5</property>
    <property name="map.abc.node.lowercase">value6</property>
    <property name="map.pqr.strFile">/path/to/file</property>
</properties>

Following is a Template(using a StringBuffer) Output to be written to a file.

abc = {
    color: {PRIMARY_COLOR:"#FFFFFF",SECONDARY_COLOR:"#F0F0F0"}
    node:{TEXT1:"value1",TEXT2:"value2"}
};

pqr = {
    color: {PRIMARY_COLOR:"#FFFFFF",SECONDARY_COLOR:"#F0F0F0"}
    node:{WORD1:"value4",WORD2:"value5"}
};

Offnote: I am using following pattern which works fine.

key.matches("map.abc.*.*\\p{Lu}$") or key.matches("map.*.*\\p{Lu}$")

I am hence looking to find a way to get all keys ending with Uppercase alphabets after the last period in the Key from the HashMap(Or possibly any other options)

you'll have to iterate through the whole set of keys and check (with regex or simply splitting the string) which ones have the last part in uppercase. — Mateusz Dymczyk
– Mateusz Dymczyk, Commented Oct 3, 2014 at 1:46
You're using the wrong data structure for the job. A database would do this quite easily. Or else you need an auxiliary map. — user207421
– user207421, Commented Oct 3, 2014 at 1:47

Peter Pei Guo · Accepted Answer · 2014-10-03 01:59:27Z

1

You can match the key with the following regex and see whether it returns true:

key.matches(".*\\.[A-Z]+");

edited Oct 3, 2014 at 1:59

answered Oct 3, 2014 at 1:44

Peter Pei Guo

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3 Comments

75inchpianist Over a year ago

thiw only works if the key ends in uppercase. his statement says any part of the key. though the examples show only ending in uppercase

Peter Pei Guo Over a year ago

One the other hand, the last line of the OP says that. I think, when he said last element, he meant the last chunk of his ". separated" string.

Cozmonaut Over a year ago

Just to clear up, if the key is "map.abc.color.SECONDARY" then I need the key which ends in uppercase after the final period. I was using the following pattern to retrieve it earlier and was working: key.matches("map.abc.*.*\\p{Lu}$") or may be key.matches("map.*.*\\p{Lu}$")

Tejay Cardon · Accepted Answer · 2014-10-04 05:42:42Z

1

OK, now that we have more detail, we can address your data structure. It appears to me that you have a hierarchical map here. Your name seems to define the hierarchy. I'd use a map of maps to store it:

Map<String, Map<String, Map<String, String>>> structure = new HashMap<>();

to parse and populate the map (totally just psuedocode):

path = name.split(".")
// ignore path[0] since it's just 'map'
structure.get(path[1]).get(path[2]).put(path[3], value)

And to retrieve values

for (Map<String, Map<String, String>> element : structure){
  for(Map<String, String> group : element) {
    for(String attribute : group.keys){
      if(allUpper(attribute)) {  //DO YOUR THING HERE }
    }
  }
}

edited Oct 4, 2014 at 5:42

answered Oct 3, 2014 at 1:48

Tejay Cardon

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Comments

clstrfsck · Accepted Answer · 2014-10-04 03:43:17Z

It looks to me like you are trying to convert from a java properties-style list of values to javascript objects.

Here is one possibility: you could "unflatten" the properties-style Map into a recursive map of maps/values, and then leverage one of the JSON libraries to output the values. Here is some code to unflatten things:

public class Foo {
  private static final String ROOT_NAME = "map";

  private static boolean noLowercase(CharSequence s) {
    return !s.chars().anyMatch(Character::isLowerCase);
  }

  private static Map<String, Object> getNextMap(Map<String, Object> map, String mapName) {
    Object nextObj = map.get(mapName);
    if (nextObj == null) {
      nextObj = new LinkedHashMap<String, Object>();
      map.put(mapName, nextObj);
    }
    @SuppressWarnings("unchecked")
    Map<String, Object> nextMap = (Map<String, Object>)nextObj;
    return nextMap;
  }

  public static Map<String, Object> unflatten(Map<String, String> properties) {
    List<String> sortedKeys = new ArrayList<>(properties.keySet());
    Collections.sort(sortedKeys);
    Map<String, Object> rootObject = new LinkedHashMap<>();
    for (String key : sortedKeys) {
      String[] splitKey = key.split("\\.");
      String lastItem = splitKey[splitKey.length - 1];
      if (noLowercase(lastItem)) {
        Map<String, Object> currentMap = rootObject;
        for (int i = 1; i < splitKey.length - 1; ++i) {
          currentMap = getNextMap(currentMap, splitKey[i]);
        }
        currentMap.put(lastItem, properties.get(key));
      }
    }
    return rootObject;
  }
}

Serialising with, for example, Gson or Jackson should be pretty easy after this. Here is an example using Gson:

  public static void printMap(Map<String, String> map) {
    Gson gson = new GsonBuilder().setPrettyPrinting().create();

    for (Map.Entry<String, Object> entry : unflatten(map).entrySet()) {
      System.out.format("%s = ", entry.getKey());
      System.out.print(gson.toJson(entry.getValue()));
      System.out.println(";");
      System.out.println();
    }
  }

Alternatively it should not be too hard to write your own printing routines for the map of maps data structure.

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