linked_list.java: Add Linked List in Java

Closes NITSkmOS#28

README.md

@@ -34,7 +34,7 @@ This repository contains examples of various algorithms written on different pro
 |:----------------------------------------------------------------------------------------------- |:-------------------------------------:|:-------------------------------------:|:-------------------------------------:|:-------------------------------------:|
 | [Queue](https://en.wikipedia.org/wiki/Queue_(abstract_data_type))                               |                                       | [:octocat:](queue/Cpp)                |                                       |                                       |
 | [Stack](https://en.wikipedia.org/wiki/Stack_(abstract_data_type))                               | [:octocat:](stack/C )                 |                                       | [:octocat:](stack/Java)               | [:octocat:](stack/Python)             |
-| [Linear Linked List](https://en.wikipedia.org/wiki/Linked_list)                                 | [:octocat:](linked_list/C)            | [:octocat:](linked_list/Cpp)          |                                       | [:octocat:](linked_list/Python)       |
+| [Linear Linked List](https://en.wikipedia.org/wiki/Linked_list)                                 | [:octocat:](linked_list/C)            | [:octocat:](linked_list/Cpp)          | [:octocat:](linked_list/Java)         | [:octocat:](linked_list/Python)       |
 | [AVL Tree](https://en.wikipedia.org/wiki/AVL_tree)                                              | [:octocat:](avl_tree/C)               | [:octocat:](avl_tree/Cpp)      | [:octocat:](avl_tree/Java)            | [:octocat:](avl_tree/Python)          |
 | [Binary Search Tree](https://en.wikipedia.org/wiki/Binary_search_tree)                          |                                       | [:octocat:](binary_search_tree/Cpp)                                       |                                       |                                       |
 | [Fenwick Tree](https://en.wikipedia.org/wiki/Fenwick_tree)                                      |                                       |                                       | [:octocat:](fenwick_tree/java)        | [:octocat:](fenwick_tree/Python)      |

linked_list/Java/linked_list.java

@@ -0,0 +1,107 @@
+public class linked_list<T> {
+    public static void main(String[] args) {
+        linked_list<String> list = new linked_list<String>("head");
+        list.add("second");
+        list.add("third");
+        list.add("last");
+        System.out.println(list.length()); // should be 4
+        System.out.println(list.remove("third")); // should print "third"
+        System.out.println(list.length()); // should be 3
+    }
+
+    private Node<T> head;
+
+    public linked_list(T head) {
+        this.head = new Node<T>(head);
+    }
+
+    public linked_list() {
+    }
+
+    /**
+     * Adds a value to the end of the list
+     *
+     * @param val value to be added
+     * @return true if add succeeds; false otherwise
+     */
+    public boolean add(T val) {
+        Node<T> tmp = this.head;
+        if (tmp == null) {
+            this.head = new Node<T>(val);
+            return true;
+        }
+
+        while (tmp.next() != null) {
+            tmp = tmp.next();
+        }
+
+        tmp.setNext(new Node<T>(val));
+        return true;
+    }
+
+    /**
+     * Returns the value that was removed if the requested value
+     * was found. Otherwise returns null if the value doesn't exist
+     * in the list
+     * @param val
+     * @return T
+     */
+    public T remove(T val) {
+        if (this.head != null) {
+            if (this.head.getValue() == val) {
+                Node<T> trash = this.head;
+                this.head = this.head.next();
+                trash.setNext(null);
+                return trash.getValue();
+            }
+        } else {
+            return null;
+        }
+
+        Node<T> prev = this.head;
+        Node<T> tmp = prev.next();
+        while (tmp != null) {
+            if (tmp.getValue() == val) {
+                prev.setNext(tmp.next());
+                tmp.setNext(null);
+                return tmp.getValue();
+            }
+            tmp = tmp.next();
+            prev = prev.next();
+        }
+
+        return null;
+    }
+
+    public int length() {
+        int len = 0;
+        Node<T> tmp = this.head;
+        while (tmp != null) {
+            len++;
+            tmp = tmp.next();
+        }
+
+        return len;
+    }
+
+    private class Node<T> {
+        private Node<T> nextNode;
+        private T value;
+
+        public Node(T val) {
+            this.value = val;
+        }
+
+        public Node<T> next() {
+            return this.nextNode;
+        }
+
+        public void setNext(Node<T> next) {
+            this.nextNode = next;
+        }
+
+        public T getValue() {
+            return this.value;
+        }
+    }
+}