diff --git a/.DS_Store b/.DS_Store
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diff --git a/Java/.DS_Store b/Java/.DS_Store
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index 0000000..270b1cb
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diff --git a/Java/algorithms/.DS_Store b/Java/algorithms/.DS_Store
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diff --git a/Java/algorithms/Huffman.java b/Java/algorithms/Huffman.java
new file mode 100644
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--- /dev/null
+++ b/Java/algorithms/Huffman.java
@@ -0,0 +1,183 @@
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileReader;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.PriorityQueue;
+
+class HuffmanNode {
+ 
+   int data;
+   char c;
+
+   HuffmanNode left;
+   HuffmanNode right;
+}
+
+class MyComparator implements Comparator<HuffmanNode> {
+   
+	public int compare(HuffmanNode x, HuffmanNode y) {
+		return x.data - y.data;
+	}
+}
+
+class HuffmanBuild {
+
+	private HashMap<Character, Integer> hash_map;
+	private HashMap<Character, String> new_hash_map; 
+	private PriorityQueue<HuffmanNode> q;
+	private String filename;
+
+	public HuffmanBuild(String filename) {
+		hash_map = new HashMap<Character, Integer>();
+		new_hash_map = new HashMap<Character, String>();
+		this.filename = filename;
+	}
+
+	private void makeFrequencyMap(Character c) {
+		
+		if (hash_map.containsKey(c)) {
+         hash_map.put(c, hash_map.get(c) + 1);
+      } else {
+         hash_map.put(c, 1);
+      }
+	}
+
+	private void makePriorityQueue() {
+		int size = hash_map.size();
+		q = new PriorityQueue<HuffmanNode>(size, new MyComparator());
+
+		for (Character alphabet : hash_map.keySet()) {
+      		HuffmanNode hn = new HuffmanNode();
+ 
+            hn.c = alphabet;
+            hn.data = hash_map.get(alphabet);
+ 
+            hn.left = null;
+            hn.right = null;
+ 
+            q.add(hn);
+    	}
+
+		generateHuffmanTree();
+	}
+
+	private void generateHuffmanTree() {
+
+		HuffmanNode root = null;
+
+		while (q.size() > 1) {
+ 
+			HuffmanNode x = q.peek();
+			q.poll();
+
+			HuffmanNode y = q.peek();
+			q.poll();
+
+			HuffmanNode f = new HuffmanNode();
+
+			f.data = x.data + y.data;
+			f.c = '-';
+
+			f.left = x;
+			f.right = y;
+
+			root = f;
+
+			q.add(f);
+      }
+
+      generateCharCode(root, "");
+      printMap();
+      printCode();
+
+	}
+
+	private void generateCharCode(HuffmanNode root, String s) {
+ 
+		if (root.left == null && root.right == null) {
+		   // System.out.println(root.c + ":" + s);
+		   new_hash_map.put(root.c, s);
+		   return;
+		}
+
+		generateCharCode(root.left, s + "0");
+		generateCharCode(root.right, s + "1");
+   }
+
+   private void printCode() {
+   	File file;
+
+		try {
+
+			file = new File(filename);
+     		BufferedReader br = new BufferedReader(new FileReader(file));
+
+     		String line;
+     		StringBuilder sb = new StringBuilder();
+
+  			while ((line = br.readLine()) != null) {
+
+  				for(int i=0; i<line.length(); i++) {
+  					char ch = line.charAt(i);
+  					sb.append(new_hash_map.get(ch));
+  				}
+
+				sb.append(new_hash_map.get('\n'));
+  			}
+
+  			String code = sb.toString();
+  			System.out.println(code);
+
+		} catch(FileNotFoundException ex) {
+    		ex.printStackTrace();
+		} catch(IOException ex){
+			ex.printStackTrace();
+		}
+   }
+
+	public void printMap() {
+		for (Character entry : new_hash_map.keySet()) {
+      		System.out.print(entry + " ");
+      		System.out.println(new_hash_map.get(entry));
+    		}
+	}
+
+	public void readFile() {
+		File file;
+
+		try {
+
+			file = new File(filename);
+     		BufferedReader br = new BufferedReader(new FileReader(file));
+
+     		String line;
+
+  			while ((line = br.readLine()) != null) {
+
+  				for(int i=0; i<line.length(); i++) {
+  					makeFrequencyMap(line.charAt(i));
+  				}
+
+				makeFrequencyMap('\n');
+  			}
+
+  			makePriorityQueue();
+
+		} catch(FileNotFoundException ex) {
+    		ex.printStackTrace();
+		} catch(IOException ex){
+			ex.printStackTrace();
+		}
+	}
+}
+
+class Huffman {
+
+	public static void main(String[] args) {
+		HuffmanBuild hf = new HuffmanBuild(args[0]);
+		hf.readFile();
+	}
+}
\ No newline at end of file
diff --git a/Java/data-structures/.DS_Store b/Java/data-structures/.DS_Store
new file mode 100644
index 0000000..ca5355c
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diff --git a/Java/data-structures/DoubleLinklist.java b/Java/data-structures/DoubleLinklist.java
new file mode 100644
index 0000000..6f84e6f
--- /dev/null
+++ b/Java/data-structures/DoubleLinklist.java
@@ -0,0 +1,153 @@
+class Node {
+	int data;
+	Node fLink;
+	Node bLink;
+
+	Node(int data) {
+		this.data = data;
+		this.fLink = this.bLink = null;
+	}
+}
+
+class DoubleLinklist {
+	private Node start;
+	private int length;
+
+	DoubleLinklist() {
+		this.start = null;
+		this.length = 0;
+	}
+
+	public void insertBeg(int data) {
+		Node newNode = new Node(data);
+
+		if(start == null) {
+			start = newNode;
+		} else {
+			start.bLink = newNode;
+			newNode.fLink = start;
+			start = newNode;
+		}
+
+		length++;
+	}
+
+	public void insetEnd(int data) {
+		Node newNode = new Node(data);
+
+		if(start == null) {
+			start = newNode;
+		} else {
+			Node n = start;
+
+			while(n.fLink != null) {
+				n = n.fLink;
+			}
+		
+			n.fLink = newNode;
+			newNode.bLink = n;
+		}
+
+		length++;
+	}
+
+	public void insetPos(int data, int pos) {
+		if(pos == 1) {
+			insertBeg(data);
+		} else if(pos > length ) {
+			insetEnd(data);
+		} else {
+
+			int i=1;
+			Node n = start;
+			
+			while( n.fLink != null ) {
+				i++;
+				if( i == pos) break;
+				n = n.fLink;
+			}
+
+			Node newNode = new Node(data);
+
+			newNode.bLink = n;
+			newNode.fLink = n.fLink;
+			n.fLink.bLink = newNode;
+			n.fLink = newNode;
+
+			length++;
+
+		}
+	}
+
+	public void deleteBeg() {
+		if(start == null) {
+			System.out.println("list empty");
+		} else {
+			start = n.fLink;
+			start.bLink = null;
+		}
+
+		length--;
+	}
+
+	public void deleteEnd() {
+		if(start == null) {
+			System.out.println("list empty");
+		} else {
+			Node n = start;
+
+			while(n.fLink.fLink != null) {
+				n = n.fLink;
+			}
+
+			n.fLink.bLink = null;
+			n.fLink = null;
+			length--;
+		}
+	}
+
+
+	public void displayForward() {
+		Node n = start;
+		while(n.fLink != null) {
+			System.out.print(n.data + " -> ");
+			n = n.fLink;
+		}
+		System.out.print(n.data + " ");
+	}
+
+	public void displayBackward() {
+		Node n = start;
+		while(n.fLink != null) {
+			n = n.fLink;
+		}
+
+		while(n.bLink != null) {
+			System.out.print(n.data + " <- ");
+			n = n.bLink;
+		}
+		System.out.print(n.data + " ");
+	}
+
+	public static void main(String[] args) {
+		doubleLinklist dl = new doubleLinklist();
+
+		dl.insertBeg(10);
+		dl.insertBeg(20);
+		dl.insertBeg(30);
+		dl.insetEnd(40);
+
+		dl.insetPos(2,4);
+
+		dl.displayForward(); // 30 -> 20 -> 10 -> 2 -> 40
+		System.out.println();
+
+		dl.deleteEnd();
+		dl.deleteBeg();
+
+		dl.displayForward(); // 20 -> 10 -> 2
+		System.out.println();
+
+		dl.displayBackward(); // 2 <- 10 <- 20
+	}
+}
\ No newline at end of file
diff --git a/Java/data-structures/LinkedList.java b/Java/data-structures/LinkedList.java
new file mode 100644
index 0000000..625de32
--- /dev/null
+++ b/Java/data-structures/LinkedList.java
@@ -0,0 +1,165 @@
+class Node {
+	int data;
+	Node link;
+
+	public Node(int data) {
+		this.data = data;
+		this.link = null;
+	}
+
+	public int getData() {
+		return data;
+	}
+}
+
+class LinkedList {
+	private Node start;
+	private int length;
+
+	LinkedList() {
+		start = null;
+		length = 0;
+	}
+
+	public void insertBeg(int data) {
+		Node newNode = new Node(data);
+
+		if(start == null) {
+			start = newNode;
+		}else {
+			newNode.link = start;
+			start = newNode;
+		}
+
+		length++;
+	}
+
+	public void insertEnd(int data) {
+		Node newNode = new Node(data);
+
+		if(start == null) {
+			start = newNode;
+		}else {
+			Node n = start;
+
+			while(n.link != null) {
+				n = n.link;
+			}
+		
+			n.link = newNode;
+		}
+
+		length++;
+	}
+
+	public void insetPos(int data, int pos) {
+		if(pos < 0) {
+			System.out.println("Pos does not");
+			return;
+		}
+
+		if(pos == 1)  {
+			insertBeg(data);
+		} else if( pos > length) {
+			insertEnd(data);
+		} else {
+			int i=1;
+			Node n = start;
+			
+			while( n.link != null ) {
+				i++;
+				if( i == pos) break;
+				n = n.link;
+			}
+
+			Node newNode = new Node(data);
+			newNode.link = n.link;
+			n.link = newNode;
+
+			length++;
+		}
+	}
+
+	public void deleteBeg() {
+		if(start == null) {
+			System.out.println("linkedlist Empty");
+		} else {
+			start = start.link;
+			length--;
+		}
+	}
+
+	public void deleteEnd() {
+		if(start == null) {
+			System.out.println("linkedlist Empty");
+		} else if(start.link == null) {
+			start = null;
+			length = 0;
+		} else {
+			Node n = start;
+
+			while(n.link.link != null) {
+				n = n.link;
+			}
+		
+			n.link = null;
+			length--;
+		}
+	}
+
+	public void deletePos(int pos) {
+		if(pos < 0) {
+			System.out.println("Pos does not");
+			return;
+		}
+
+		if(pos == 1)  {
+			deleteBeg();
+		} else if( pos > length) {
+			deleteEnd();
+		} else {
+			int i=1;
+			Node n = start;
+			
+			while( n.link != null ) {
+				i++;
+				if( i == pos) break;
+				n = n.link;
+			}
+
+			n.link = n.link.link;
+			length--;
+		}
+	}
+
+	public void display() {
+		Node n = start;
+
+		while(n != null) {
+			System.out.print(n.data + " ");
+			n = n.link;
+		}
+		System.out.println();
+	}
+	
+	public static void main(String[] args) {
+		LinkedList sl = new LinkedList();
+
+		sl.insertBeg(10);
+		sl.insertBeg(20);
+		sl.insertBeg(30);
+		sl.insertEnd(40);
+		
+		sl.insetPos(60,5);
+		sl.insetPos(5,5);
+
+		sl.display();
+		sl.deleteBeg();
+		sl.display();
+		sl.deleteEnd();
+		sl.display();
+		sl.deletePos(2);
+		sl.display();
+	}
+
+}