Add Key and Value into an Priority Queue and Sort by Key in Java

问题

I am trying to take in a List of strings and add them into a Priority Queue with Key and Value. The Key being the word and the value being the string value of the word. Then I need to sort the queue with the highest string value first. The priority queue is not letting me add 2 values.

public static List<String> pQSortStrings(List<String> strings) {
    PriorityQueue<String, Integer> q = new PriorityQueue<>();

    for (int x = 0; x < strings.size(); x++) {
        q.add(strings.get(x),calculateStringValue(strings.get(x)));
    }
    return strings;
}

回答1:

Problem

PriorityQueue can store a single object in it's each node. So what you are trying to do can not be done as it is.

But you can compose both objects in a single class and then use the PriorityQueue.

You would either need to supply a Comparator or rely on natural ordering by implementing Comparable interface.

Solution

Create a class which has String and int as it's members.

public class Entry {
    private String key;
    private int value;

    // Constructors, getters etc.
}

Implement Comparable interface and delegate comparison to String.

public class Entry implements Comparable<Entry> {
    private String key;
    private int value;

    public Entry(String key, int value) {
        this.key = key;
        this.value = value;
    }

    // getters

    @Override
    public int compareTo(Entry other) {
        return this.getKey().compareTo(other.getKey());
    }
}

Build the PriorityQueue using this class.

PriorityQueue<Entry> q = new PriorityQueue<>();

Add elements as following.

q.add(new Entry(strings.get(x), calculateStringValue(strings.get(x))));

Hope this helps.

回答2:

Using Java-8

PriorityQueue<Map.Entry<String, Integer>> queue = new PriorityQueue<>((a, b)->b.getValue()-a.getValue());

to add a new Entry

queue.offer(new AbstractMap.SimpleEntry<>("A", 10));

来源：https://stackoverflow.com/questions/29872664/add-key-and-value-into-an-priority-queue-and-sort-by-key-in-java

标签

java

priority-queue