List

ArrayList

package com.sjp.list;

import java.io.Serializable;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 * Created by Timor on 2019/6/24.
 */
public class MyArrayList<E> implements Serializable {

    private static final long serialVersionUID = -4561713656026223332L;

    private static final Object[] DEFAULTCAPACITY_EMPTY_ELEMENTDATA = {};
    transient Object[] elementData;//存放元素
    private int size;//数组长度
    //每个结构性改变的方法中modCount自增1，主要是为了避免在遍历集合时对集合进行更改，ConcurrentModificationException
    private transient int modCount = 0;

    public MyArrayList() {
        this.elementData = DEFAULTCAPACITY_EMPTY_ELEMENTDATA;
    }

    public boolean add(E e) {
        modCount++;
        elementData[size++] = e;
        return true;
    }

    public E get(int index) {
        if (index >= size)
            throw new IndexOutOfBoundsException("Index: "+index+", Size: "+size);

        return (E) elementData[index];
    }

    public boolean remove(Object o) {
        if (o == null) {
            for (int index = 0; index < size; index++)
                if (elementData[index] == null) {
                    fastRemove(index);
                    return true;
                }
        } else {
            for (int index = 0; index < size; index++)
                if (o.equals(elementData[index])) {
                    fastRemove(index);
                    return true;
                }
        }
        return false;
    }

    public void clear() {
        modCount++;

        // clear to let GC do its work
        for (int i = 0; i < size; i++)
            elementData[i] = null;

        size = 0;
    }

    public Iterator<E> iterator() {
        return new Itr();
    }

    /**
     * An optimized version of AbstractList.Itr
     */
    private class Itr implements Iterator<E> {
        int cursor;       // index of next element to return
        int lastRet = -1; // index of last element returned; -1 if no such
        int expectedModCount = modCount;

        Itr() {}

        public boolean hasNext() {
            return cursor != size;
        }

        @SuppressWarnings("unchecked")
        public E next() {
            checkForComodification();
            int i = cursor;
            if (i >= size)
                throw new NoSuchElementException();
            Object[] elementData = MyArrayList.this.elementData;
            if (i >= elementData.length)
                throw new ConcurrentModificationException();
            cursor = i + 1;
            return (E) elementData[lastRet = i];
        }

        public void remove() {
            if (lastRet < 0)
                throw new IllegalStateException();
            checkForComodification();

            try {
                MyArrayList.this.remove(lastRet);
                cursor = lastRet;
                lastRet = -1;
                expectedModCount = modCount;
            } catch (IndexOutOfBoundsException ex) {
                throw new ConcurrentModificationException();
            }
        }

        final void checkForComodification() {
            if (modCount != expectedModCount)
                throw new ConcurrentModificationException();
        }
    }

    private void fastRemove(int index) {
        modCount++;
        int numMoved = size - index - 1;
        if (numMoved > 0)
            System.arraycopy(elementData, index+1, elementData, index,
                    numMoved);
        elementData[--size] = null; // clear to let GC do its work
    }



}

Vector

ArrayList的线程安全版，synchronized修饰

LinkedList

package com.sjp.list;

import java.io.Serializable;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.NoSuchElementException;

/**
 * Created by Timor on 2019/6/24.
 */
public class MyLinkedList<E> implements Serializable {

    private static final long serialVersionUID = -6451303013610399227L;

    transient int size = 0;
    private transient int modCount = 0;
    transient Node<E> first;//第一个节点
    transient Node<E> last;//最后一个节点

    /**
     * 头插
     * @param e
     */
    public void addFirst(E e) {
        final Node<E> f = first;
        final Node<E> newNode = new Node<E>(null, e, f);
        first = newNode;
        if (f == null)
            last = newNode;
        else
            f.prev = newNode;
        size++;
        modCount++;
    }

    /**
     * 尾插
     * @param e
     */
    public void addLast(E e) {
        final Node<E> l = last;
        final Node<E> newNode = new Node<E>(l, e, null);
        last = newNode;
        if (l == null)
            first = newNode;
        else
            l.next = newNode;
        size++;
        modCount++;
    }

    /**
     * 查找
     * @param index
     * @return
     */
    public E get(int index) {
        if (index < 0 || index >= size)
            throw new IndexOutOfBoundsException("Index: "+index+", Size: "+size);
        if (index < (size >> 1)) {
            Node<E> x = first;
            for (int i = 0; i < index; i++)
                x = x.next;
            return x.item;
        } else {
            Node<E> x = last;
            for (int i = size - 1; i > index; i--)
                x = x.prev;
            return x.item;
        }
    }
    
    /**
     * 移除
     * @param o
     * @return
     */
    public boolean remove(Object o) {
        if (o == null) {
            for (Node<E> x = first; x != null; x = x.next) {
                if (x.item == null) {
                    unlink(x);
                    return true;
                }
            }
        } else {
            for (Node<E> x = first; x != null; x = x.next) {
                if (o.equals(x.item)) {
                    unlink(x);
                    return true;
                }
            }
        }
        return false;
    }

    private E unlink(Node<E> x) {
        // assert x != null;
        final E element = x.item;
        final Node<E> next = x.next;
        final Node<E> prev = x.prev;

        if (prev == null) {
            first = next;
        } else {
            prev.next = next;
            x.prev = null;
        }

        if (next == null) {
            last = prev;
        } else {
            next.prev = prev;
            x.next = null;
        }

        x.item = null;
        size--;
        modCount++;
        return element;
    }

    private static class Node<E> {
        E item;
        Node<E> next;
        Node<E> prev;

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