Java Implementation of LFU

.gitignore

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+/LFU/nbproject/private/
+/LFU/build/
+/LFU/dist/

Java/FrequencyList.java

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+package lfu;
+import java.util.LinkedList;
+import java.util.ListIterator;
+
+class FrequencyList<T> {
+	int frequency;
+	LinkedList<T> list;
+
+	FrequencyList(){
+		list = new LinkedList<T>();
+	}
+	FrequencyList(int f){
+		list = new LinkedList<T>();
+		frequency = f;
+	}
+
+	public void add(T t){
+		list.add(t);
+	}
+
+	public void remove(T t){
+		list.remove(t);
+	}
+
+	public ListIterator<T> listIterator(int index){
+		return list.listIterator(index);
+	}	
+
+	public int size(){
+		return list.size();
+	}
+
+	public T get(int index){
+		return list.get(index);
+	}
+
+	public int getFrequency(){
+		return frequency;
+	}
+}

Java/LFU.java

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+package lfu;
+import java.util.LinkedList;
+import java.util.ListIterator;
+import java.util.HashMap;
+
+/**
+ * @author salman
+ * @param <T>
+ */
+
+public class LFU<T> {
+
+	private int MAX_SIZE = 2;
+
+	private LinkedList< FrequencyList<T> > lfuList;
+	private HashMap<T, Pair<Integer, ListIterator<T> > > nodeFrequencyMap;
+	private HashMap<Integer, ListIterator< FrequencyList<T> > > frequencyMap;
+	private int count = 0;
+
+	public void init() {		
+		lfuList = new LinkedList< FrequencyList<T> >();
+		nodeFrequencyMap = new HashMap<T, Pair<Integer, ListIterator<T> > >();
+
+		frequencyMap = new HashMap<Integer, ListIterator< FrequencyList<T> > >();
+		count = 0;
+	}
+
+	LFU(){
+		init();
+	}
+
+	LFU(int size){
+		MAX_SIZE = size;
+		init();
+	}
+
+	public void insert(T item){
+		if(count >= MAX_SIZE)
+			delete();
+
+		// If frequencyList is empty
+		if(!frequencyMap.containsKey(1)){
+			lfuList.listIterator(0).add(new FrequencyList(1));
+			frequencyMap.put(1, lfuList.listIterator(0));
+		}
+
+		ListIterator< FrequencyList<T> > fListIt = frequencyMap.get(1);
+		FrequencyList<T> frequencyList = fListIt.next();
+		fListIt.previous();
+		frequencyList.listIterator(frequencyList.size()).add(item);
+
+		// Update item frequency
+		nodeFrequencyMap.put(item, new Pair(1, frequencyList.listIterator(frequencyList.size() - 1)));
+
+		// Update Count
+		count++;
+	}
+
+	public boolean lookup(T item){
+
+		// If item does not exist
+		if(!nodeFrequencyMap.containsKey(item)){
+			insert(item);
+			return false;
+		}
+
+		// If item exists
+		// Get FrequencyList of item
+		int frequency          = nodeFrequencyMap.get(item).first;
+		ListIterator<T> nodeIt = nodeFrequencyMap.get(item).second;
+		ListIterator< FrequencyList<T> > fListIt = frequencyMap.get(frequency);
+		FrequencyList<T> frequencyList = fListIt.next();
+
+		fListIt.previous();
+		System.out.println(item + " " + frequency + " " + frequencyList.getFrequency() + " " + fListIt);
+
+		// Remove Item from current frequencyList
+		nodeIt.next();
+		nodeIt.previous();
+		nodeIt.remove();
+
+		// Check if frequencyList is empty
+		if(frequencyList.size() == 0){
+			// Clean Up
+			frequencyMap.remove(frequencyList.getFrequency());
+			fListIt.remove();
+		}
+
+		// Add item to list frequency + 1
+		frequency++;
+
+		// If frequencyList is empty
+		if(!frequencyMap.containsKey(frequency)){
+			fListIt.add(new FrequencyList(frequency));
+			fListIt.previous();
+			frequencyMap.put(frequency, fListIt);
+		}
+
+		frequencyList = fListIt.next();
+		fListIt.previous();
+		frequencyList.listIterator(frequencyList.size()).add(item);
+
+		// Update item frequency
+		nodeIt = frequencyList.listIterator(frequencyList.size() - 1);
+		nodeFrequencyMap.put(item, new Pair(frequency, nodeIt));
+		return true;
+	}
+
+	public T delete(){
+		ListIterator< FrequencyList<T> > fListIt = lfuList.listIterator(0);
+		FrequencyList<T> frequencyList = fListIt.next();
+
+		fListIt.previous();
+		T item = frequencyList.get(0);
+		ListIterator<T> nodeIt = nodeFrequencyMap.get(item).second;
+
+		nodeIt.next();
+		nodeIt.remove();
+		nodeFrequencyMap.remove(item);
+
+		if(frequencyList.size() == 0){
+			// Clean Up
+			frequencyMap.remove(frequencyList.getFrequency());
+			fListIt.remove();
+		}
+
+		// Update Count
+		count--;
+		System.out.println("Deleted "+item);
+		return item;
+	}
+
+	public static void main(String args[]) {
+		LFU<Integer> freqlfu = new LFU();
+
+		freqlfu.insert(10);
+
+		System.out.println(freqlfu.lookup(10));
+		System.out.println(freqlfu.lookup(10));
+		System.out.println(freqlfu.lookup(20));
+		System.out.flush();
+		System.out.println(freqlfu.lookup(10));
+	}
+}

Java/Pair.java

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+package lfu;
+
+class Pair<U, V> {
+	U first;
+	V second;
+
+	Pair(){}
+
+	Pair(U u, V v){
+		first = u;
+		second = v;
+	}
+
+}