双链表 LinkedList

实现代码

package com.lhs;public class LinkedList<E> implements List<E>{// 定义链表长度private int size;// 定义头节点private Node<E> first;// 定义尾节点private Node<E> last;// 内部类，定义节点public static class Node<E>{// 定义节点数据E data;// 定义下一个节点Node<E> next;// 定义前一个节点Node<E> pre;// 构造函数，用于创建新的节点Node(E data,Node<E> next,Node<E> pre){this.data = data;this.next = next;this.pre = pre;}}// 重写size方法，返回链表长度@Overridepublic int size() {return size;}// 重写isEmpty方法，判断链表是否为空@Overridepublic boolean isEmpty() {return size == 0;}// 重写contains方法，判断链表是否包含某元素@Overridepublic boolean contains(Object o) {return IndexOf(o) >= 0;}// 重写IndexOf方法，返回某元素在链表中的位置public int IndexOf(Object o){Node<E> node = first;if (o == null){for (int i = 0; i < size; i++) {if (node.data == null){return i;}node = node.next;}return -1;}else{for (int i = 0; i < size; i++) {if (o.equals(node.data)){return i;}node = node.next;}return -1;}}// 重写add方法，向链表末尾添加元素@Overridepublic boolean add(E e) {if (size == 0){Node<E> node = new Node<>(e, null, null);first = node;last = node;}else{Node<E> l = last;Node<E> node = new Node<>(e, null, l);l.next = node;last = node;}size++;return true;}// 重写get方法，返回链表中指定位置的元素@Overridepublic E get(int index) {if(index >= size){throw new IndexOutOfBoundsException(index + " out of bound");}Node<E> node;if(index > (size >> 1)){node = last;for(int i = 0 ; i<size - index - 1;i++){node = node.pre;}}else{node = first;for (int i = 0; i < size - index - 1; i++) {node = node.next;}}return node.data;}// 重写set方法，替换链表中指定位置的元素@Overridepublic E set(int index, E e) {if(index >= size){throw new IndexOutOfBoundsException(index + " out of bound");}E oldVal;Node<E> node;if(index > (size >> 1)){node = last;for(int i = 0 ; i<size - index - 1;i++){node = node.pre;}}else{node = first;for (int i = 0; i < size - index - 1; i++) {node = node.next;}}oldVal = node.data;node .data = e;return oldVal;}// 重写remove方法，移除链表中指定位置的元素@Overridepublic E remove(int index) {if(index >= size){throw new IndexOutOfBoundsException(index + " out of bound");}Node<E> node;if(index > (size >> 1)){node = last;for(int i = 0 ; i<size - index - 1;i++){node = node.pre;}}else{node = first;for (int i = 0; i < size - index - 1; i++) {node = node.next;}}E oldVal = node.data;Node<E> n = node.next;Node<E> p = node.pre;if(p != null){p.next = n;}else{first = n;}if(n != null){n.pre = p;}else{last = p;}size--;return oldVal;}// 重写addFirst方法，向链表头部添加元素@Overridepublic void addFirst(E e) {Node<E> f = first;Node<E> node = new Node<>(e, null, f);f.pre = node;first = node;size++;}// 重写addLast方法，向链表尾部添加元素@Overridepublic void addLast(E e) {add(e);}// 重写removeFirst方法，移除链表头部元素@Overridepublic E removeFirst() {return remove(0);}// 重写removeLast方法，移除链表尾部元素@Overridepublic E removeLast() {return remove(size-1);}
}

测试代码

/*** Welcome to https://waylau.com*/
package com.lhs;import org.junit.Test;import java.util.LinkedList;
import java.util.List;import static junit.framework.TestCase.*;
import static org.junit.Assert.assertThrows;/*** LinkedList Test.* * @since 1.0.0 2020年5月4日* @author <a href="https://waylau.com">Way Lau</a>*/
public class LinkedListTests {@Testpublic void testSize() {// 实例化LinkedListList<String> list = new LinkedList<String>();assertTrue(list.size() == 0);list.add("Java");assertTrue(list.size() == 1);}@Testpublic void testIsEmpty() {// 实例化LinkedListList<String> list = new LinkedList<String>();assertTrue(list.isEmpty());list.add("Java");assertFalse(list.isEmpty());}@Testpublic void testContains() {// 实例化LinkedListList<String> list = new LinkedList<String>();list.add("Java");list.add("C++");list.add("C");list.add("Python");list.add("TypeScript");// 判断存在assertTrue(list.contains("Java"));// 判断不存在assertFalse(list.contains("Java++"));}@Testpublic void testAdd() {// 实例化LinkedListList<Integer> list = new LinkedList<Integer>();list.add(1);list.add(2);list.add(3);list.add(4);list.add(5);assertFalse(list.isEmpty());}@Testpublic void testGet() {// 实例化LinkedListList<String> list = new LinkedList<String>();list.add("Java");list.add("C++");list.add("C");// 判断存在assertEquals("C++", list.get(1));// 判断不存在int index = 6;Throwable excpetion = assertThrows(IndexOutOfBoundsException.class, () -> {list.get(index);// 抛异常});assertNotNull(excpetion.getMessage());}@Testpublic void testSet() {// 实例化LinkedListList<String> list = new LinkedList<String>();list.add("Java");list.add("C++");list.add("C");// 判断存在assertEquals("C", list.set(2, "Python"));// 判断不存在int index = 6;Throwable excpetion = assertThrows(IndexOutOfBoundsException.class, () -> {list.set(index, "Python");// 抛异常});assertNotNull(excpetion.getMessage());}@Testpublic void testRemove() {// 实例化LinkedListList<String> list = new LinkedList<String>();list.add("Java");list.add("C++");list.add("C");// 判断存在assertEquals("C", list.remove(2));assertEquals("C++", list.remove(1));assertEquals("Java", list.get(0));// 判断不存在int index = 6;Throwable excpetion = assertThrows(IndexOutOfBoundsException.class, () -> {list.remove(index); // 抛异常});assertNotNull(excpetion.getMessage());}@Testpublic void testAddFirst() {// 实例化LinkedListLinkedList<String> list = new LinkedList<String>();list.addFirst("Java");list.addFirst("C++");list.addFirst("C");// 判断存在assertEquals("C", list.get(0));assertEquals("C++", list.get(1));assertEquals("Java", list.get(2));}@Testpublic void testAddLast() {// 实例化LinkedListLinkedList<String> list = new LinkedList<String>();list.addLast("Java");list.addLast("C++");list.addLast("C");// 判断存在assertEquals("Java", list.get(0));assertEquals("C++", list.get(1));assertEquals("C", list.get(2));}@Testpublic void testRemoveFirst() {// 实例化LinkedListLinkedList<String> list = new LinkedList<String>();list.add("Java");list.add("C++");list.add("C");// 判断存在assertEquals("Java", list.removeFirst());assertEquals("C++", list.removeFirst());assertEquals("C", list.removeFirst());}@Testpublic void testRemoveLast() {// 实例化LinkedListLinkedList<String> list = new LinkedList<String>();list.add("Java");list.add("C++");list.add("C");// 判断存在assertEquals("C", list.removeLast());assertEquals("C++", list.removeLast());assertEquals("Java", list.removeLast());}}