Yesterday I was using a HashMap, and I wanted a quick snippet of code that allowed me to sort the map by either it’s keys or values. I’ve only scratched the surface of all the java Collections classes, so I don’t know if this already exists, but I present a sortable map!
Usage:
SortableMap<String, Integer> map = new SortableMap<String, Integer>();
map.put("Bubble", Integer.valueOf(2));
map.put("Grape", Integer.valueOf(1));
map.sortValues();
for (String key : map.getKeys()) {
System.out.println(key + " -> " + map.get(key));
}
[icode]SortableMap.java[/icode]
package com.digiturtle.game;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
public class SortableMap<K extends Comparable<K>, V extends Comparable<V>> {
private ArrayList<K> keys = new ArrayList<K>();
private ArrayList<V> values = new ArrayList<V>();
public void put(K key, V value) {
keys.add(key);
values.add(value);
}
public V get(K key) {
return values.get(keys.indexOf(key));
}
public void remove(K key) {
values.remove(get(key));
keys.remove(key);
}
public boolean containsKey(K key) {
return keys.indexOf(key) >= 0;
}
public void sortKeys() {
sortKeys(null);
}
public void sortKeys(Comparator<K> comparator) {
ArrayList<K> clonedKeys = new ArrayList<K>();
ArrayList<V> clonedValues = new ArrayList<V>();
clonedKeys.addAll(keys);
clonedValues.addAll(values);
if (comparator == null)
Collections.sort(keys);
else
Collections.sort(keys, comparator); // sort the keys
// add all values
values.clear();
for (K key : keys) {
values.add(clonedValues.get(clonedKeys.indexOf(key)));
}
}
public void sortValues() {
sortValues(null);
}
public void sortValues(Comparator<V> comparator) {
ArrayList<K> clonedKeys = new ArrayList<K>();
ArrayList<V> clonedValues = new ArrayList<V>();
clonedKeys.addAll(keys);
clonedValues.addAll(values);
if (comparator == null)
Collections.sort(values);
else
Collections.sort(values, comparator); // sort the keys
// add all values
keys.clear();
for (V value : values) {
keys.add(clonedKeys.get(clonedValues.indexOf(value)));
}
}
public ArrayList<K> getKeys() {
return keys;
}
public ArrayList<V> getValues() {
return values;
}
public static void performUnitTest(String[] keySet, String[] valueSet) {
SortableMap<String, String> map = new SortableMap<String, String>();
for (int index = 0; index < keySet.length; index++) {
map.put(keySet[index], valueSet[index]);
}
System.out.println("Start unit test");
// map.sortKeys();
map.sortValues();
for (String key : map.getKeys()) {
System.out.println(key + " -> " + map.get(key));
}
System.out.println("Stop unit test");
}
}
This is just a snippet that I wrote for my own uses, and thought I should post it just in case anybody else has an interest 