CODEWITHSUNDEEP
javahashmaphashtableshufflelinkedhashmap
MDT
MDT

Reputation: 1659

Best structure for list of key-value (integer, string) to be shuffled

I need to implement a structure in Java that is a key-value list (of types Integer-String) and I want to shuffle it.

Basically, I would like to do something like that.

    public LinkedHashMap<Integer, String> getQuestionOptionsMap(){

    LinkedHashMap<Integer, String>  shuffle = new LinkedHashMap<Integer, String> ();

    if (answer1 != null)
        shuffle.put(new Integer(1), answer1);
    if (answer2 != null)
        shuffle.put(new Integer(2), answer2);
    if (answer3 != null)
        shuffle.put(new Integer(3), answer3);
    if (answer4 != null) 
        shuffle.put(new Integer(4), answer4);

    Collections.shuffle(shuffle);
    return shuffle;
}

However, HashMap cannot be shuffled.

I could randomly get a key from the hashmap, and then return the linked element, but I'm sure this is not the best solution for my problem.

Is there any better way?

Thanks in advance.

Upvotes: 9

Views: 119846

Answers (5)

laudarch
laudarch

Reputation: 1123

You can use enum to achieve this, example

package device.packet.data;

public enum TLVList {
    
    SpeedingAlarm(0x1001, 3, Short.class),
    LowVoltageAlarm(0x1002, 3, Short.class),
    OBDCommunicationError(0x1015, 3, Short.class),
    IgnitionOn(0x1016, 3, Short.class),
    IgnitionOff(0x1017, 3, Short.class),
    MILAlarm(0x1018, 3, Short.class),
    UnlockAlarm(0x1019, 3, Short.class),
    NoCardPresented(0x101A, 3, Short.class),
    HiddenCommand(0x101B, 3, Short.class),
    Vibration(0x101C, 3, Short.class),
    DoorOpened(0x101D, 3, Short.class);
    
    private int tagFlagHex;
    private int length;
    private Class aClass;

    public int gettagFlagHex() {
        return tagFlagHex;
    }

    public int getLength() {
        return length;
    }

    public Class getClassType() {
        return aClass;
    }

    TLVList(int tagFlagHex, int length, Class aClass) {

        this.tagFlagHex = tagFlagHex;
        this.length = length;
        this.aClass = aClass;
    }

    public static TLVList of(Integer tagFlagHex) {
        for (TLVList tagFlag : TLVList.values()) {
            if(tagFlag.tagFlagHex == tagFlagHex) return tagFlag;
        }
        return null;
    }
}

I hope it helps.

Upvotes: 0

Oleg Mikhailov
Oleg Mikhailov

Reputation: 6081

Hashtable<Integer, String>

As an alternative to less convenient and effective List<SomePairClass<Integer, String>>

Upvotes: 0

Peter Lawrey
Peter Lawrey

Reputation: 533502

You can keep the Map. The Map is designed to be looked up by key so I suggest you have a list of shuffled keys.

public Map<Integer, String> getQuestionOptionsMap() {
    Map<Integer, String> map = new HashMap<>();
    String[] answers = {null, answer1, answer2, answer3, answer4};
    for (int i = 1; i < answers.length; i++)
        if (answers[i] != null)
            map.put(i, answers[i]);
    List<Integer> order = new ArrayList<>(map.keySet());
    Collections.shuffle(order);
    Map<Integer, String> shuffled = new LinkedHashMap<>();
    for (Integer key : order)
        shuffled.put(key, map.get(key));
    return shuffled;
}

Upvotes: 8

Kayaman
Kayaman

Reputation: 73548

You could keep a separate List of the keyvalues, shuffle that and use it to access the HashMap.

List<Integer> keys = new ArrayList<Integer>(map.keySet());
Collections.shuffle(keys);
for(Integer i : keys)
    map.get(i);     // Gets the values in the shuffled order

Upvotes: 2

Konstantin Yovkov
Konstantin Yovkov

Reputation: 62864

Create a Pair class, that holds both the Integer and the String and then add multiple Pair objects to a List, which will be shuffled.

public class Pair {
  private Integer integer;

  private String string;

  //accessors
}

Then:

List<Pair> list = new ArrayList<Pair>();
//...add some Pair objects to the list
Collections.shuffle(list);

Upvotes: 15

Related Questions