Get the keys with the biggest values from a hashmap?

Question

I have a HashMap defined like this...

HashMap uniqueNames = new HashMap();

It stor

Answer 1

Seems like you want something a bit like a SortedMap but one sorted on the value, not the key. I don't think such a thing exists in the standard API.

It might be better to create a Frequency class and store instances in a SortedSet instead.

import java.util.Set;
import java.util.TreeSet;

public class Frequency implements Comparable {

  private String name;
  private int freq;

  public Frequency(String name, int freq) {
    this.name = name;
    this.freq = freq;
  }

  public static void main(String[] args) {
    Set set = new TreeSet();

    set.add(new Frequency("fred", 1));
    set.add(new Frequency("bob", 5));
    set.add(new Frequency("jim", 10));
    set.add(new Frequency("bert", 4));
    set.add(new Frequency("art", 3));
    set.add(new Frequency("homer", 5));

    for (Frequency f : set) {
      System.out.println(f);
    }
  }

  @Override
  public boolean equals(Object o) {
    if (o == null) return false;
    if (o.getClass().isAssignableFrom(Frequency.class)) {
      Frequency other = (Frequency)o;
      return other.freq == this.freq && other.name.equals(this.name);
    } else {
      return false;
    }
  }

  @Override
  public int compareTo(Frequency other) {
    if (freq == other.freq) {
      return name.compareTo(other.name);
    } else {
      return freq - other.freq;
    }
  }

  @Override
  public String toString() {
    return name + ":" + freq;
  }

}

Output:

fred:1
art:3
bert:4
bob:5
homer:5
jim:10