Revision: 1131
http://cishell.svn.sourceforge.net/cishell/?rev=1131&view=rev
Author: kongchinhua
Date: 2010-09-07 19:15:01 +0000 (Tue, 07 Sep 2010)
Log Message:
-----------
Support Frequency counting
- It is important to use key with unmodified value with deep comp[are of equal function
- Safe to use with generic objects: String, Integer, etc
- Non-generic class need customized equal and hashcode method
Added Paths:
-----------
trunk/core/org.cishell.utilities/src/org/cishell/utilities/FrequencyMap.java
Added: trunk/core/org.cishell.utilities/src/org/cishell/utilities/FrequencyMap.java
===================================================================
--- trunk/core/org.cishell.utilities/src/org/cishell/utilities/FrequencyMap.java (rev 0)
+++ trunk/core/org.cishell.utilities/src/org/cishell/utilities/FrequencyMap.java 2010-09-07 19:15:01 UTC (rev 1131)
@@ -0,0 +1,107 @@
+package org.cishell.utilities;
+
+import java.util.HashMap;
+import java.util.Hashtable;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * FrequencyMap is a map of key with its emergence frequency.
+ * It supports two type of mapping structures: null key and
+ * non-null key; by providing boolean value to enable
+ * allowNullValue through constructor call. Add() method will
+ * add a new key if the key is not exist. Else it will increase
+ * the frequency by 1. sum() will return the count that
+ * represents sum of all the frequency values in the map
+ * @author kongch
+ *
+ * @param <E>
+ */
+public class FrequencyMap <E> {
+ private Map<E, Frequency> itemToFrequencyMap;
+ private int count;
+
+ public FrequencyMap(boolean allowNullValue) {
+ count = 0;
+ if (allowNullValue) {
+ itemToFrequencyMap = new HashMap<E, Frequency>();
+ } else {
+ itemToFrequencyMap = new Hashtable<E, Frequency>();
+ }
+ }
+
+ /**
+ * Add the given key to the map and increase the frequency by 1
+ * @param key - key to be added
+ */
+ public void add(E key) {
+ Frequency frequency;
+
+ /*
+ * Get the Frequency object for the given key if key already exist.
+ * Else create a new Frequency object and add it to the map
+ */
+ if (itemToFrequencyMap.containsKey(key)) {
+ frequency = itemToFrequencyMap.get(key);
+ } else {
+ frequency = new Frequency();
+ try {
+ itemToFrequencyMap.put(key, frequency);
+ } catch (NullPointerException e) {
+ /* It is a non-null map. Throw a runtime exception */
+ String message = "FrequencyMap.add(E key) was called with a null key."
+ + " If null support is desired, "
+ + " construct FrequencyMap with allowNullValue = true";
+ throw new NullValueSupportException(message, e);
+ }
+ }
+
+ /* increase frequency by 1 and also sum of all frequencies by 1 */
+ count++;
+ frequency.increase();
+ }
+
+ /**
+ * Retrieve a set of keys stored in this map
+ */
+ public Set<E> keySet() {
+ return itemToFrequencyMap.keySet();
+ }
+
+ /**
+ * Get the emergence frequency for the given key
+ * @param key - item to be lookup
+ * @return Return number of times the key exists
+ * if lookup success. Return zero if key not exist
+ */
+ public int getFrequency(E key) {
+ if (itemToFrequencyMap.containsKey(key)) {
+ return itemToFrequencyMap.get(key).getValue();
+ } else {
+ return 0;
+ }
+ }
+
+ public int sum() {
+ return count;
+ }
+
+ public boolean isEmpty() {
+ return itemToFrequencyMap.isEmpty();
+ }
+
+ private class Frequency {
+ private int value;
+ public Frequency() {
+ value = 0;
+ }
+
+ public void increase() {
+ value++;
+ }
+
+ public int getValue() {
+ return value;
+ }
+ }
+}
Property changes on: trunk/core/org.cishell.utilities/src/org/cishell/utilities/FrequencyMap.java
___________________________________________________________________
Added: svn:mime-type
+ text/plain
This was sent by the SourceForge.net collaborative development platform, the world's largest Open Source development site.
|
