详细介绍：手写ArrayList和LinkedList

项目仓库：https://gitee.com/bossDuy/hand-tear-collection-series
基于b站up生生大佬：https://www.bilibili.com/video/BV1Kp5tzGEc5/?spm_id_from=333.788.videopod.sections&vd_source=4cda4baec795c32b16ddd661bb9ce865

LinkedList

package com.yb0os1.List
;
import java.util.Iterator
;
import java.util.NoSuchElementException
;
import java.util.Objects
;
public
class MyLinkedList<
E>
implements List<
E> {
private
int size;
private Node<
E> tail;
//尾节点
private Node<
E> head;
//头节点
@Override
//尾插法
public
void add(E element) {
Node<
E> node =
new Node<
>(tail, element,
null
)
;
//尾插法
if (tail !=
null
) tail.next = node;
else head = node;
tail = node;
++size;
}
@Override
//对应的下标插入元素
public
void add(E element,
int index) {
//先判断index是否合法
if (index <
0 || index > size) {
throw
new IndexOutOfBoundsException("index:" + index + "size:" + size)
;
}
//尾插
if (size == index) {
add(element)
;
return
;
}
//中间插入 先找到在那个位置插入
Node<
E> indexNode = findNode(index)
;
Node<
E> newNode =
new Node<
>(indexNode.prev, element, indexNode)
;
if (indexNode.prev ==
null
) {
//代表indexNode是头节点
head = newNode;
}
else {
indexNode.prev.next = newNode;
}
indexNode.prev = newNode;
++size;
}
private Node<
E> findNode(
int index) {
Node<
E> cur = head;
while (index-- >
0
) {
cur = cur.next;
}
return cur;
}
@Override
public E remove(
int index) {
//先判断index是否合法
if (index <
0 || index >= size) {
throw
new IndexOutOfBoundsException("index:" + index + "size:" + size)
;
}
//找到要删除的节点
Node<
E> indexNode = findNode(index)
;
if (indexNode.prev ==
null
) {
//头节点
head = indexNode.next;
}
else{
//非头节点
indexNode.prev.next = indexNode.next;
}
if (indexNode.next ==
null
) {
//尾节点
tail = indexNode.prev;
}
else {
//非尾节点
indexNode.next.prev = indexNode.prev;
}
indexNode.next =
null
;
indexNode.prev =
null
;
--size;
return indexNode.value;
}
@Override
public
boolean remove(E element) {
Node<
E> curNode = head;
int index = 0
;
while (curNode !=
null
) {
if (Objects.equals(element, curNode.value)
) {
remove(index)
;
return true
;
}
++index;
curNode = curNode.next;
}
return false
;
}
@Override
public E set(E element,
int index) {
//先判断index是否合法
if (index <
0 || index >= size) {
throw
new IndexOutOfBoundsException("index:" + index + "size:" + size)
;
}
Node<
E> indexNode = findNode(index)
;
E oldValue = indexNode.value;
indexNode.value = element;
return oldValue;
}
@Override
public E get(
int index) {
//先判断index是否合法
if (index <
0 || index >= size) {
throw
new IndexOutOfBoundsException("index:" + index + "size:" + size)
;
}
Node<
E> indexNode = findNode(index)
;
return indexNode.value;
}
@Override
public
int size(
) {
return size;
}
/**
* Returns an iterator over elements of type {@code T}.
*
* @return an Iterator.
*/
@Override
public Iterator<
E> iterator(
) {
return
new LinkedListIterator(
)
;
}
private
class LinkedListIterator
implements Iterator<
E> {
Node<
E> curNode = head;
@Override
public
boolean hasNext(
) {
return curNode!=
null
;
}
/**
* Returns the next element in the iteration.
*
* @return the next element in the iteration
* @throws NoSuchElementException if the iteration has no more elements
*/
@Override
public E next(
) {
if (curNode==
null
){
throw
new NoSuchElementException(
)
;
}
E value = curNode.value;
curNode = curNode.next;
return value;
}
}
private
class Node<
E> {
E value;
Node<
E> next;
//后继
Node<
E> prev;
//前驱
public Node(E value) {
this.value = value;
}
public Node(Node<
E> prev, E value, Node<
E> next) {
this.value = value;
this.next = next;
this.prev = prev;
}
}
}

ArrayList

package com.yb0os1.List
;
import java.util.Iterator
;
import java.util.NoSuchElementException
;
import java.util.Objects
;
public
class MyArrayList<
E>
implements List<
E> {
private Object[] table;
//默认
private
final
static
int DEFAULT_CAPACITY = 10
;
//默认容量
private
int size;
//实际的大小
public MyArrayList(
) {
this.table =
new Object[DEFAULT_CAPACITY]
;
}
public MyArrayList(
int initialCapacity) {
if (initialCapacity <
0
)
throw
new IllegalArgumentException("Illegal Capacity: " +
initialCapacity)
;
this.table =
new Object[initialCapacity]
;
}
//插入一个元素，在size的位置插入元素 也就是尾端插入元素
@Override
public
void add(E element) {
//先判断size是否等于容量，等于的话需要先扩容，不等于才可以插入
if (size >= table.length) {
resize(
)
;
}
table[size++] = element;
}
//在对应的index插入元素
@Override
public
void add(E element,
int index) {
//先判断index是否合法
if (index <
0 || index > size) {
throw
new IndexOutOfBoundsException("Index: " + index + ", Size: " + size)
;
}
//判断是否需要扩容后
if (table.length == size) {
resize(
)
;
}
//插入逻辑，也就是在0~size的位置插入元素了 需要后移
System.arraycopy(table, index, table, index + 1
, size - index)
;
table[index] = element;
size++
;
}
//删除对应下标位置的元素
@Override
public E remove(
int index) {
System.out.println( "remove(int index)"
)
;
//先判断index是否合法
if (index <
0 || index >= size) {
throw
new IndexOutOfBoundsException("Index: " + index + ", Size: " + size)
;
}
E oldElement = (E
) table[index]
;
System.arraycopy(table, index + 1
, table, index, size - index - 1
)
;
table[--size] =
null
;
return oldElement;
}
@Override
public
boolean remove(Object element) {
System.out.println( "remove(Object element)"
)
;
for (
int i = 0
; i < size; i++
) {
if (Objects.equals(element, table[i]
)
) {
remove(i)
;
return true
;
}
}
return false
;
}
//修改下标为index位置的元素为element
@Override
public E set(E element,
int index) {
//先判断index是否合法
if (index <
0 || index >= size) {
throw
new IndexOutOfBoundsException("Index: " + index + ", Size: " + size)
;
}
E oldElement = (E
) table[index]
;
table[index] = element;
return oldElement;
}
@Override
public E get(
int index) {
//先判断index是否合法
if (index <
0 || index >= size) {
throw
new IndexOutOfBoundsException("Index: " + index + ", Size: " + size)
;
}
return (E
) table[index]
;
}
@Override
public
int size(
) {
return
this.size;
}
//数组扩容的逻辑
private
void resize(
) {
//1.5倍扩容
Object[] newTable =
new Object[table.length + (table.length >>
1
)]
;
System.out.println("扩容了,原数组大小" + table.length + ",现在数组大小" + newTable.length)
;
// 从内存的角度把一个数组元素的引用装到另外一个数组上
System.arraycopy(table, 0
, newTable, 0
, table.length)
;
this.table = newTable;
}
/**
* Returns an iterator over elements of type {@code T}.
*
* @return an Iterator.
*/
@Override
public Iterator<
E> iterator(
) {
return
new ArrayIterator(
)
;
}
private
class ArrayIterator
implements Iterator<
E> {
int cursor = 0
;
//判断是否有下一个元素
@Override
public
boolean hasNext(
) {
return cursor != size;
}
@Override
public E next(
) {
if (!hasNext(
)
)
throw
new NoSuchElementException(
)
;
return (E
) table[cursor++]
;
}
}
}