Linked List implementation #linkedlist #java

LinkedList.java

/**
 * Created by hoangong on 23/12/2015.
 */
public class LinkedList {

    private Node head;
    private Node tail;
    private int count;

    public Node getHead() {
        return head;
    }

    public Node getTail() {
        return tail;
    }

    public void add(Node i) {
        if(i == null)
            return;
        if (head == null) {
            setHead(i);
            setTail(i);
        } else {
            getTail().setNext(i);
            setTail(i);
        }
        count++;
    }

    public void setHead(Node head) {
        this.head = head;
    }

    public void setTail(Node tail) {
        this.tail = tail;
    }

    public int getCount() {
        return count;
    }

    @Override
    public String toString() {
        Node cur = getHead();
        StringBuilder s = new StringBuilder();
        while (cur != null) {
            if (s.toString().equals("")) {
                s.append(cur.getValue());
            } else {
                s.append(" -> " + cur.getValue());
            }
            cur = cur.getNext();
        }
        return s.toString();
    }

    public Node find(int i) {
        Node cur = getHead();
        while (cur != null) {
            if(cur.getValue() == i)
                return cur;
            cur = cur.getNext();
        }
        return null;
    }

    public void delete(int i) {
        Node pre = null;
        Node cur = getHead();
        while (cur != null) {
            if(cur.getValue() == i){
                if(pre == null){
                    setHead(cur.getNext());
                } else {
                    pre.setNext(cur.getNext());
                }
                count--;
                return;
            }
            pre = cur;
            cur = cur.getNext();
        }
    }
}

class Node {
    private final Integer value;
    private Node next;

    public Node(Integer i, Node next) {
        this.value = i;
        this.next = next;
    }

    public void setNext(Node next){
        this.next = next;
    }

    public Integer getValue() {
        return value;
    }

    public Node getNext() {
        return next;
    }
}

LinkedListTest.java

import org.junit.Test;

import static org.junit.Assert.*;

/**
 * Created by hoangong on 23/12/2015.
 */
public class LinkedListTest {
    @Test
    public void createEmptyLLWithEmptyHeadAndTail(){
        LinkedList ll = new LinkedList();
        assertEquals(null,ll.getHead());
        assertEquals(null,ll.getTail());
    }

    @Test
    public void setFirstItemWillSetAsHeadAndTail(){
        LinkedList ll = new LinkedList();
        Node i = new Node(1, null);
        ll.add(i);
        assertEquals(i,ll.getHead());
        assertEquals(i,ll.getTail());
    }

    @Test
    public void setNotFirstItemAppendToTheBottom(){
        LinkedList ll = new LinkedList();
        Node i1 = new Node(1, null);
        Node i2 = new Node(2, null);
        Node i3 = new Node(3, null);
        ll.add(i1);
        ll.add(i2);
        ll.add(i3);
        assertEquals(i1,ll.getHead());
        assertEquals(i3,ll.getTail());
    }

    @Test
    public void canCount(){
        LinkedList ll = new LinkedList();
        Node i1 = new Node(1, null);
        Node i2 = new Node(2, null);
        Node i3 = new Node(3, null);
        ll.add(i1);
        ll.add(i2);
        ll.add(i3);
        assertEquals(3,ll.getCount());
    }

    @Test
    public void cannotAddNull(){
        LinkedList ll = new LinkedList();
        Node i1 = new Node(1, null);
        Node i2 = new Node(2, null);
        Node i3 = new Node(3, null);
        ll.add(i1);
        ll.add(i2);
        ll.add(i3);
        ll.add(null);
        assertEquals(3,ll.getCount());
    }

    @Test
    public void printLL(){
        LinkedList ll = new LinkedList();
        Node i1 = new Node(1, null);
        Node i2 = new Node(2, null);
        Node i3 = new Node(3, null);
        ll.add(i1);
        ll.add(i2);
        ll.add(i3);
        assertEquals("1 -> 2 -> 3", ll.toString());
    }

    @Test
    public void printEmpty(){
        LinkedList ll = new LinkedList();
        assertEquals("", ll.toString());
    }

    @Test
    public void findAnItem(){
        LinkedList ll = new LinkedList();
        Node i1 = new Node(1, null);
        Node i2 = new Node(2, null);
        Node i3 = new Node(3, null);
        ll.add(i1);
        ll.add(i2);
        ll.add(i3);
        Node find = ll.find(2);
        assertEquals(i2, find);
    }

    @Test
    public void notFindAnItem(){
        LinkedList ll = new LinkedList();
        Node i1 = new Node(1, null);
        Node i2 = new Node(2, null);
        Node i3 = new Node(3, null);
        ll.add(i1);
        ll.add(i2);
        ll.add(i3);
        Node find = ll.find(5);
        assertEquals(null, find);
    }

    @Test
    public void deleteItem(){
        LinkedList ll = new LinkedList();
        Node i1 = new Node(1, null);
        Node i2 = new Node(2, null);
        Node i3 = new Node(3, null);
        ll.add(i1);
        ll.add(i2);
        ll.add(i3);
        ll.delete(2);
        assertEquals(2, ll.getCount());
        assertEquals(i1, ll.getHead());
        assertEquals(i3, ll.getTail());

        ll.delete(3);
        assertEquals(1, ll.getCount());
        assertEquals(i1, ll.getHead());

        ll.delete(1);
        assertEquals(0, ll.getCount());
        assertEquals(null, ll.getHead());
    }

    @Test
    public void deleteNonExistItem(){
        LinkedList ll = new LinkedList();
        Node i1 = new Node(1, null);
        Node i2 = new Node(2, null);
        Node i3 = new Node(3, null);
        ll.add(i1);
        ll.add(i2);
        ll.add(i3);
        ll.delete(5);
        assertEquals(3, ll.getCount());
        assertEquals(i1, ll.getHead());
        assertEquals(i3, ll.getTail());
    }
}