LinkedList封装

Posted 2021-01-30 startseven

LinkedList简单的封装

package com.cn.test.jihe.LinkedList;

import java.util.NoSuchElementException;

public class LinkedList {

    // 头结点
    Node<Object> first;
    // 尾指针
    Node<Object> last;
    private int size; // 记录要插入的元素的总数

    LinkedList() {

    }

    /**
     * 将指定元素添加到此列表的结尾。
     * 
     * @param obj
     * @return insert
     */
    boolean add(Object obj) {
        linkLast(obj);
        return true;
    }

    private void linkLast(Object obj) {
        Node l = last;
        Node<Object> newNode = new Node<Object>(l, obj, null);
        last = newNode; // 记录下次要插入的前驱节点
        if (l == null) {
            first = newNode;
        } else {
            l.next = newNode;
        }
        size++;
    }

    /**
     * 在此列表中指定的位置插入指定的元素。
     * 
     * @throws Exception
     *             insert
     */
    void add(int index, Object element) throws Exception {
        // 判断要插入的位置
        rangeCheckIndex(index);
        // 循环遍历要插入的位置
        insertElement(index, element);
        size++;
    }

    private void insertElement(int index, Object element) {
        int count = 0;
        Node temp = first;
        // 在头部进行插入
        if (index == 0) {
            if (temp != null) {
                Node newNode = new Node(null, element, temp);
                temp.prev = newNode;
                first = newNode;
            } else {
                Node tempLast = last;
                Node newNode = new Node(tempLast, element, null);
                last = newNode;
                first = newNode;
            }
            return;
        }
        // 在尾部进行插入
        if (index != 0 && index == size) {
            Node tempLast = last;
            Node newNode = new Node(tempLast, element, null);
            last = newNode;
            tempLast.next = newNode;
            return;
        }
        // 不是在头部或者尾部进行插入
        while (temp != null) { //
            if (count == index) {
                // 找到要插入的位置 temp这个节点表示要插入的节点的位置
                Node newNode = new Node(temp.prev, element, null);
                newNode.prev.next = newNode;
                temp.prev = newNode;
                newNode.next = temp;
            }
            temp = temp.next;
            count++;
        }

    }

    private void rangeCheckIndex(int index) throws Exception {
        if (index < 0 || index > size)
            throw new Exception("下标越界");
    }

    /**
     * 返回列表中指定的元素
     * 
     * @param index
     * @return
     * @throws Exception
     *             select
     */
    Object get(int index) throws Exception {
        rangeCheckOut(index);
        Node temp = first;
        int count = 0;
        while (temp != null) {
            if (count == index) {
                return temp.item;
            }
            count++;
            temp = temp.next;
        }
        return null;
    }

    /**
     * 返回此列表的第一个元素。
     * 
     * @throws Exception
     */
    Object getFirst() throws Exception {
        Node temp = first;
        if (temp == null) {
            throw new Exception("该集合没有元素");
        }
        return temp.item;
    }

    /**
     * 返回最后一个元素
     * 
     * @return
     * @throws Exception
     * 
     */
    Object getLast() throws Exception {
        Node temp = last;
        if (temp == null) {
            throw new Exception("该集合没有元素");
        }
        return temp.item;
    }

    /**
     * 返回此列表中首次出现的指定元素的索引，如果此列表中不包含该元素，则返回 -1。
     * 
     * @param o
     * @return
     */
    public int indexOf(Object o) {
        int count = 0;
        Node temp = first;
        if (o == null) {
            while (temp != null) {
                if (null == temp.item) {
                    return count;
                }
                count++;
                temp = temp.next;
            }
        } else {
            while (temp != null) {
                if (o.equals(temp.item)) {
                    return count;
                }
                count++;
                temp = temp.next;
            }
        }
        return -1;
    }

    /**
     * 
     * 返回此列表中最后出现的指定元素的索引， 如果此列表中不包含该元素，则返回 -1。
     */
    public int lastIndexOf(Object o) {
        int index = size - 1;
        if (null == o) {
            for (Node temp = last; temp != null; temp = temp.prev) {
                if (null == temp.item) {
                    return index;
                }
                index--;
            }
        } else {
            for (Node temp = last; temp != null; temp = temp.prev) {
                if (o.equals(temp.item)) {
                    return index;
                }
                index--;
            }
        }
        return -1;
    }

    public int size() {
        return size;
    }

    private void rangeCheckOut(int index) throws Exception {
        if (index < 0 || index >= size) {
            throw new Exception("下标越界" + index);
        }

    }

    /**
     * 删除 获取并移除此列表的头（第一个元素）。
     * 
     * @throws Exception
     */
    Object remove() throws Exception {
        if (first == null) {
            throw new Exception("链表为空");
        }
        Node oldNode = first;
        first = oldNode.next;
        if (first != null) {
            first.prev = null;
        } else {
            last = null;
        }
        size--;
        return oldNode.item;
    }

    /**
     * 移除此列表中指定位置处的元素。
     * 
     * @param index
     * @throws Exception
     */

    Object remove(int index) throws Exception {
        // 判断长度是否超限
        rangeCheckOut(index);
        // 确认要删除的节点
        Node oldNode = getIndexNode(index);
        unLinkNode(oldNode);
        return oldNode.item;
    }

    /**
     * remove(Object o) 从此列表中移除首次出现的指定元素（如果存在）。
     */
    boolean remove(Object o) {
        // 列表是否有该元素 ， 如果有返回该节点
        Node oldNode = checkeElement(o);
        if (oldNode != null) {
            unLinkNode(oldNode);
            return true;
        }
        return false;
    }

    /**
     * 移除并返回此列表的第一个元素
     * 
     * @return
     * @throws Exception
     */
    Object removeFirst() throws Exception {
        if (first == null) {
            throw new Exception("linkedList is null");
        }
        Object oldValue = first.item;
        first = first.next;
        if (first == null) {
            last = null;
        } else {
            first.next.prev = null;
        }
        size--;
        return oldValue;
    }

    /**
     * 移除最后一个元素
     * 
     * @return
     */
    public Object removeLast() {
        Node l = last;
        if (l == null)
            throw new NoSuchElementException();
        return unlinkLast(l);
    }

    /**
     * 将此列表中指定位置的元素替换为指定的元素。
     * 
     * @param index
     * @param element
     * @return
     * @throws Exception
     */
    public Object set(int index, Object element) throws Exception {
        // 判断要插入的索引的位置
        rangeCheckOut(index);
        // 获取要插入位置的节点
        Node indexNode = getIndexNode(index);
        Object oldValue = indexNode.item;
        indexNode.item = element;
        return oldValue;
    }

    /**
     * 返回以适当顺序（从第一个元素到最后一个元素）包含此列表中所有元素的数组
     * 
     * @return
     */
    public Object[] toArray() {
        Object[] result = new Object[size];
        int count = 0;
        for (Node temp = first; temp != null; temp = temp.next) {
            result[count] = temp.item;
            count++;
        }
        return result;
    }

    private Object unlinkLast(Node l) {
        final Object element = l.item;
        Node prev = l.prev;
        l.item = null;
        l.prev = null; // help GC
        last = prev;
        if (prev == null) {
            first = null;
        } else {
            last.next = null;
        }

        size--;
        return l.item;
    }

    private Node checkeElement(Object o) {
        if (o == null) {
            // 循环遍历链表
            for (Node temp = first; temp != null; temp = temp.next) {
                if (null == temp.item) {
                    return temp;
                }
            }
        } else {
            for (Node temp = first; temp != null; temp = temp.next) {
                if (o.equals(temp.item)) {
                    return temp;
                }
            }
        }
        return null;
    }

    /**
     * 取消链表节点之间的关系
     * 
     * @param oldValue
     */
    private void unLinkNode(Node oldNode) {
        Node beforeNode = oldNode.prev;
        Node afterNode = oldNode.next;
        if (beforeNode == null) {
            // 要删除的节点是头节点
            first = afterNode;
            afterNode.prev = null;
        }
        if (afterNode == null) {
            // 要删除的节点是尾节点
            last = beforeNode;
            beforeNode.next = null;
        }

        if (beforeNode != null && afterNode != null) {
            // 删除的非头节点和非尾节点 修改指针的位置
            beforeNode.next = afterNode;
            afterNode.prev = beforeNode;
        }
        size--;
    }

    /**
     * 找到要删除的节点
     * 
     * @param index
     */
    private Node getIndexNode(int index) {
        if (index < (size >> 1)) {
            // 删除节点的位置为链表的前半段
            Node firstNode = first;
            for (int i = 0; i < index; i++) {
                firstNode = firstNode.next;
            }
            return firstNode;
        } else {
            Node lastNode = last;
            for (int i = --size; i > index; i--) {
                lastNode = last.prev;
            }
            return lastNode;
        }
    }

    private Object removeAfterNode(int index) {
        // 首先迭代
        int count = 0;
        for (Node temp = first; temp != null; count++) {
            if (index == count) {
                // 找到要删除的节点进行删除
                Object oldValue = temp.item;
                Node previous = temp.prev;
                Node after = temp.next;
                previous.next = after;

                size--;
                return oldValue;
            }
            temp = temp.next;
        }
        return null;
    }

    /**
     * 采用双链表
     */
    private static class Node<Object> {
        Object item;
        Node<Object> next; // 下一个节点
        Node<Object> prev; // 前驱节点

        Node(Node<Object> prev, Object element, Node<Object> next) {
            this.item = element;
            this.next = next;
            this.prev = prev;
        }

        Node(Object item) {
            this.item = item;
        }
    }
}

testCast

/*

        LinkedList list = new LinkedList();
        list.add(1);
        list.add(1, 2);
        list.add(2);
        list.add(3);
        list.add(2,8);
        list.add(0,4);
        list.add(1,2);
        list.add(0,8);
        list.add(2);
        list.add(5);
        System.out.println(list.size());
    //    System.out.println(list);
        Object first = list.getFirst();
        System.out.println("fist=" + (int)first);
        Object last = list.getLast();
        System.out.println("last=" + (int)last);
        int indexOf = list.indexOf(10);
        System.out.println("indexof=" + indexOf);
        int lastIndexOf = list.lastIndexOf(100);
        System.out.println("lastIndex=" + lastIndexOf);
        LinkedList list2 = new LinkedList();
        list2.add(2);
        Object remove = list2.remove();
        for (int i=0; i<list.size();i++) {
            System.out.print("i=" + (int)list.get(i) + " ");
        }
        Object remove = list.remove(0);
        System.out.println("remove=" + remove);
        list.add(130);
        for (int i=0; i<list.size();i++) {
            System.out.print("i=" + (int)list.get(i) + " ");
        }
        System.out.println();
        list.remove(new Integer(4));
        for (int i=0; i<list.size();i++) {
            System.out.print("j1=" + (int)list.get(i) + " ");
        }
        System.out.println();
         list.add(0,89);
         list.add(8,129);
         list.removeFirst();
         list.removeFirst();
         System.out.println("------------------");
         for (int i=0; i<list.size();i++) {
                System.out.print("j2=" + (int)list.get(i) + " ");
            }
    */
        LinkedList list2 = new LinkedList();
        list2.add(new String("a"));
        list2.removeFirst();
        list2.add(new String("b"));
//        list2.add(new String("c"));
    //    list2.remove(new String("c"));
        list2.removeLast();
        list2.add(new String("c"));
        list2.add(new String("d"));
        list2.removeLast();
    //    list2.removeLast();
        list2.add(new String("f"));
        list2.set(0, new String("222"));
        list2.add(1, new String("14"));
        //list2.removeLast();
         for (int i=0; i<list2.size();i++) {
                System.out.print("j3=" + (String)list2.get(i) + " ");
            }