From 673c747a7c0b90f8a8aa7c3cf59e787b2f08722d Mon Sep 17 00:00:00 2001
From: simpleman594 <wlkybg@163.com>
Date: Sun, 8 Mar 2020 23:27:30 +0800
Subject: [PATCH 1/2] 	new file:  
 "second/week_01/89/ArrayList\346\272\220\347\240\201\345\210\206\346\236\220.md"
 	new file:  
 "second/week_01/89/HashMap\346\272\220\347\240\201\345\210\206\346\236\220.md"
 	new file:  
 "second/week_01/89/LinkedList\346\272\220\347\240\201\345\210\206\346\236\220.md"

---
 .idea/workspace.xml                           | 218 ++++++++++++++++++
 ...20\347\240\201\345\210\206\346\236\220.md" | 161 +++++++++++++
 ...20\347\240\201\345\210\206\346\236\220.md" | 125 ++++++++++
 ...20\347\240\201\345\210\206\346\236\220.md" | 114 +++++++++
 4 files changed, 618 insertions(+)
 create mode 100644 .idea/workspace.xml
 create mode 100644 "second/week_01/89/ArrayList\346\272\220\347\240\201\345\210\206\346\236\220.md"
 create mode 100644 "second/week_01/89/HashMap\346\272\220\347\240\201\345\210\206\346\236\220.md"
 create mode 100644 "second/week_01/89/LinkedList\346\272\220\347\240\201\345\210\206\346\236\220.md"

diff --git a/.idea/workspace.xml b/.idea/workspace.xml
new file mode 100644
index 0000000..aee8cca
--- /dev/null
+++ b/.idea/workspace.xml
@@ -0,0 +1,218 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ChangeListManager">
+    <list default="true" id="849f0ad2-7b24-4b58-93af-d82b889f0304" name="Default Changelist" comment="">
+      <change beforePath="$PROJECT_DIR$/.idea/workspace.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/workspace.xml" afterDir="false" />
+    </list>
+    <option name="SHOW_DIALOG" value="false" />
+    <option name="HIGHLIGHT_CONFLICTS" value="true" />
+    <option name="HIGHLIGHT_NON_ACTIVE_CHANGELIST" value="false" />
+    <option name="LAST_RESOLUTION" value="IGNORE" />
+  </component>
+  <component name="DefaultGradleProjectSettings">
+    <option name="isMigrated" value="true" />
+  </component>
+  <component name="Git.Settings">
+    <option name="RECENT_GIT_ROOT_PATH" value="$PROJECT_DIR$" />
+  </component>
+  <component name="JsFlowSettings">
+    <service-enabled>true</service-enabled>
+    <exe-path />
+    <other-services-enabled>true</other-services-enabled>
+    <auto-save>true</auto-save>
+  </component>
+  <component name="MavenImportPreferences">
+    <option name="generalSettings">
+      <MavenGeneralSettings>
+        <option name="mavenHome" value="D:/software/apache-maven-3.5.3" />
+        <option name="userSettingsFile" value="D:\software\apache-maven-3.5.3\conf\settings.xml" />
+      </MavenGeneralSettings>
+    </option>
+    <option name="importingSettings">
+      <MavenImportingSettings>
+        <option name="vmOptionsForImporter" value="-Xmx768m" />
+      </MavenImportingSettings>
+    </option>
+  </component>
+  <component name="MavenRunner">
+    <option name="jreName" value="1.8" />
+  </component>
+  <component name="ProjectId" id="1W0KnGQQ4lLywjMN8yfRPmdRp8q" />
+  <component name="ProjectViewState">
+    <option name="hideEmptyMiddlePackages" value="true" />
+    <option name="showExcludedFiles" value="true" />
+    <option name="showLibraryContents" value="true" />
+  </component>
+  <component name="PropertiesComponent">
+    <property name="ASKED_SHARE_PROJECT_CONFIGURATION_FILES" value="true" />
+    <property name="SHARE_PROJECT_CONFIGURATION_FILES" value="true" />
+    <property name="SONARLINT_PRECOMMIT_ANALYSIS" value="true" />
+    <property name="WebServerToolWindowFactoryState" value="false" />
+    <property name="aspect.path.notification.shown" value="true" />
+    <property name="com.android.tools.idea.instantapp.provision.ProvisionBeforeRunTaskProvider.myTimeStamp" value="1577631985552" />
+    <property name="last_opened_file_path" value="$PROJECT_DIR$" />
+    <property name="node.js.detected.package.eslint" value="true" />
+    <property name="node.js.detected.package.tslint" value="true" />
+    <property name="node.js.path.for.package.eslint" value="project" />
+    <property name="node.js.path.for.package.tslint" value="project" />
+    <property name="node.js.selected.package.eslint" value="(autodetect)" />
+    <property name="node.js.selected.package.tslint" value="(autodetect)" />
+    <property name="nodejs_interpreter_path.stuck_in_default_project" value="undefined stuck path" />
+    <property name="nodejs_npm_path_reset_for_default_project" value="true" />
+    <property name="settings.editor.selected.configurable" value="MavenSettings" />
+  </component>
+  <component name="RecentsManager">
+    <key name="CopyFile.RECENT_KEYS">
+      <recent name="D:\algorithm\JavaStudy" />
+      <recent name="D:\algorithm\JavaStudy\week_01" />
+      <recent name="D:\algorithm\JavaStudy\week_01\1" />
+    </key>
+  </component>
+  <component name="ServiceViewManager">
+    <option name="viewStates">
+      <list>
+        <serviceView>
+          <treeState>
+            <expand />
+            <select />
+          </treeState>
+        </serviceView>
+      </list>
+    </option>
+  </component>
+  <component name="SvnConfiguration">
+    <configuration />
+  </component>
+  <component name="TaskManager">
+    <task active="true" id="Default" summary="Default task">
+      <changelist id="849f0ad2-7b24-4b58-93af-d82b889f0304" name="Default Changelist" comment="" />
+      <created>1575821822704</created>
+      <option name="number" value="Default" />
+      <option name="presentableId" value="Default" />
+      <updated>1575821822704</updated>
+      <workItem from="1575821824264" duration="165000" />
+      <workItem from="1575875016778" duration="3254000" />
+      <workItem from="1576919866029" duration="2346000" />
+      <workItem from="1577625639335" duration="2076000" />
+      <workItem from="1578281241942" duration="1055000" />
+      <workItem from="1578659116978" duration="424000" />
+      <workItem from="1578708676818" duration="862000" />
+      <workItem from="1578919635767" duration="694000" />
+      <workItem from="1579450587735" duration="274000" />
+      <workItem from="1580545712385" duration="1022000" />
+    </task>
+    <task id="LOCAL-00001" summary="目录创建">
+      <created>1575879326719</created>
+      <option name="number" value="00001" />
+      <option name="presentableId" value="LOCAL-00001" />
+      <option name="project" value="LOCAL" />
+      <updated>1575879326719</updated>
+    </task>
+    <task id="LOCAL-00002" summary="059_week02">
+      <created>1576937212682</created>
+      <option name="number" value="00002" />
+      <option name="presentableId" value="LOCAL-00002" />
+      <option name="project" value="LOCAL" />
+      <updated>1576937212683</updated>
+    </task>
+    <task id="LOCAL-00003" summary="059_week03">
+      <created>1577625846275</created>
+      <option name="number" value="00003" />
+      <option name="presentableId" value="LOCAL-00003" />
+      <option name="project" value="LOCAL" />
+      <updated>1577625846275</updated>
+    </task>
+    <task id="LOCAL-00004" summary="059_week03">
+      <created>1577626057128</created>
+      <option name="number" value="00004" />
+      <option name="presentableId" value="LOCAL-00004" />
+      <option name="project" value="LOCAL" />
+      <updated>1577626057128</updated>
+    </task>
+    <task id="LOCAL-00005" summary="059_week04">
+      <created>1578281384211</created>
+      <option name="number" value="00005" />
+      <option name="presentableId" value="LOCAL-00005" />
+      <option name="project" value="LOCAL" />
+      <updated>1578281384211</updated>
+    </task>
+    <task id="LOCAL-00006" summary="059_week05">
+      <created>1578659146286</created>
+      <option name="number" value="00006" />
+      <option name="presentableId" value="LOCAL-00006" />
+      <option name="project" value="LOCAL" />
+      <updated>1578659146286</updated>
+    </task>
+    <task id="LOCAL-00007" summary="059_week05_补充">
+      <created>1578919897465</created>
+      <option name="number" value="00007" />
+      <option name="presentableId" value="LOCAL-00007" />
+      <option name="project" value="LOCAL" />
+      <updated>1578919897465</updated>
+    </task>
+    <task id="LOCAL-00008" summary="059_week06">
+      <created>1579450655843</created>
+      <option name="number" value="00008" />
+      <option name="presentableId" value="LOCAL-00008" />
+      <option name="project" value="LOCAL" />
+      <updated>1579450655843</updated>
+    </task>
+    <task id="LOCAL-00009" summary="059_week06_增强任务及补充">
+      <created>1580545769184</created>
+      <option name="number" value="00009" />
+      <option name="presentableId" value="LOCAL-00009" />
+      <option name="project" value="LOCAL" />
+      <updated>1580545769184</updated>
+    </task>
+    <option name="localTasksCounter" value="10" />
+    <servers />
+  </component>
+  <component name="TypeScriptGeneratedFilesManager">
+    <option name="version" value="1" />
+  </component>
+  <component name="VcsManagerConfiguration">
+    <MESSAGE value="目录创建" />
+    <MESSAGE value="059_week02" />
+    <MESSAGE value="059_week03" />
+    <MESSAGE value="059_week04" />
+    <MESSAGE value="059_week05" />
+    <MESSAGE value="059_week05_补充" />
+    <MESSAGE value="059_week06" />
+    <MESSAGE value="059_week06_增强任务及补充" />
+    <option name="LAST_COMMIT_MESSAGE" value="059_week06_增强任务及补充" />
+  </component>
+  <component name="WindowStateProjectService">
+    <state x="385" y="10" key="CommitChangelistDialog2" timestamp="1580545767703">
+      <screen x="0" y="0" width="1536" height="824" />
+    </state>
+    <state x="385" y="10" key="CommitChangelistDialog2/0.0.1536.824@0.0.1536.824" timestamp="1580545767703" />
+    <state x="549" y="171" key="FileChooserDialogImpl" timestamp="1580546136643">
+      <screen x="0" y="0" width="1536" height="824" />
+    </state>
+    <state x="549" y="171" key="FileChooserDialogImpl/0.0.1536.824@0.0.1536.824" timestamp="1580546136643" />
+    <state x="361" y="149" key="Vcs.Push.Dialog.v2" timestamp="1580545772138">
+      <screen x="0" y="0" width="1536" height="824" />
+    </state>
+    <state x="361" y="149" key="Vcs.Push.Dialog.v2/0.0.1536.824@0.0.1536.824" timestamp="1580545772138" />
+    <state x="461" y="241" key="com.intellij.ide.util.TipDialog" timestamp="1578708675877">
+      <screen x="0" y="0" width="1536" height="824" />
+    </state>
+    <state x="461" y="241" key="com.intellij.ide.util.TipDialog/0.0.1536.824@0.0.1536.824" timestamp="1578708675877" />
+  </component>
+  <component name="masterDetails">
+    <states>
+      <state key="ProjectJDKs.UI">
+        <settings>
+          <last-edited>1.8</last-edited>
+          <splitter-proportions>
+            <option name="proportions">
+              <list>
+                <option value="0.2" />
+              </list>
+            </option>
+          </splitter-proportions>
+        </settings>
+      </state>
+    </states>
+  </component>
+</project>
\ No newline at end of file
diff --git "a/second/week_01/89/ArrayList\346\272\220\347\240\201\345\210\206\346\236\220.md" "b/second/week_01/89/ArrayList\346\272\220\347\240\201\345\210\206\346\236\220.md"
new file mode 100644
index 0000000..945c021
--- /dev/null
+++ "b/second/week_01/89/ArrayList\346\272\220\347\240\201\345\210\206\346\236\220.md"
@@ -0,0 +1,161 @@
+# ArrayList 源码分析
+
+
+## 总体概述
+ 
+ArrayList是动态数组的一种实现。内部基于数组。它的优点是它可以快速查询元素，但是插入删除大概率需要移动大量元素。因此，ArrayList适用于频繁查询元素且添加删除较少的场景。
+
+## 成员变量
+
+ - transient Object[] elementData; //存储数组数据
+ 
+ - private int size; //数组数据大小
+ 
+ 
+## 构造方法
+
+```java
+
+    /**
+    * 根据initialCapacity创建数组或抛异常
+    */
+    public ArrayList(int initialCapacity) {
+        if (initialCapacity > 0) {
+            this.elementData = new Object[initialCapacity];
+        } else if (initialCapacity == 0) {
+            this.elementData = EMPTY_ELEMENTDATA;
+        } else {
+            throw new IllegalArgumentException("Illegal Capacity: "+
+                                               initialCapacity);
+        }
+    }
+
+    /**
+     * 没有参数构造函数，将DEFAULTCAPACITY_EMPTY_ELEMENTDATA值分配给elementData
+     */
+    public ArrayList() {
+        this.elementData = DEFAULTCAPACITY_EMPTY_ELEMENTDATA;
+    }
+
+    /**
+     *传入集合，首先调用toArray方法将集合转化成为Object[]。如果数组为0，则初始化为空数组
+     * 
+     */
+    public ArrayList(Collection<? extends E> c) {
+        elementData = c.toArray();
+        if ((size = elementData.length) != 0) {
+            // c.toArray might (incorrectly) not return Object[] (see 6260652)
+            //疑问：elementData定义为Object[]，为何有如下判断
+            if (elementData.getClass() != Object[].class)
+                elementData = Arrays.copyOf(elementData, size, Object[].class);
+        } else {
+            // replace with empty array.
+            this.elementData = EMPTY_ELEMENTDATA;
+        }
+```    
+    
+
+##add方法
+
+```java
+
+    private static final int DEFAULT_CAPACITY = 10;
+    public boolean add(E e) {
+        //确定数组大小，根据条件扩容数组
+        ensureCapacityInternal(size + 1);  // Increments modCount!!
+        //将新增元素插入末尾
+        elementData[size++] = e;
+        return true;
+    }
+    private void ensureCapacityInternal(int minCapacity) {
+        //calculateCapacity 计算数组容量
+            ensureExplicitCapacity(calculateCapacity(elementData, minCapacity));
+        }
+
+    private static int calculateCapacity(Object[] elementData, int minCapacity) {
+        //如果是无参构造，容量为10，否则返回size + 1
+            if (elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA) {
+                return Math.max(DEFAULT_CAPACITY, minCapacity);
+            }
+            return minCapacity;
+        }
+        
+    private void ensureExplicitCapacity(int minCapacity) {
+            modCount++;
+    
+            // overflow-conscious code
+            //如果+1后的容量>原数组大小，则需要扩容
+            if (minCapacity - elementData.length > 0)
+                grow(minCapacity);
+        }
+
+    private void grow(int minCapacity) {
+         // overflow-conscious code
+         int oldCapacity = elementData.length;
+         //扩容新容量newCapacity = oldCapacity + oldCapacity/2
+         int newCapacity = oldCapacity + (oldCapacity >> 1);
+         if (newCapacity - minCapacity < 0)
+             newCapacity = minCapacity;
+         if (newCapacity - MAX_ARRAY_SIZE > 0)
+             newCapacity = hugeCapacity(minCapacity);
+         // minCapacity is usually close to size, so this is a win:
+         elementData = Arrays.copyOf(elementData, newCapacity);
+     }
+     
+    //如果新计算的 minCapacity 是负数，则抛出异常。如果大于MAX_ARRAY_SIZE则minCapacity赋值为Integer.MAX_VALUE
+    private static int hugeCapacity(int minCapacity) {
+        if (minCapacity < 0) // overflow
+            throw new OutOfMemoryError();
+        return (minCapacity > MAX_ARRAY_SIZE) ?
+            Integer.MAX_VALUE :
+            MAX_ARRAY_SIZE;
+    }
+
+```
+
+##get
+
+```
+
+    public E get(int index) {
+        //检查一下传入下标
+        rangeCheck(index);
+        //返回index对应元素
+        return elementData(index);
+    }
+```
+
+##remove
+```java
+
+    public boolean remove(Object o) {
+        //遍历数组，删除元素
+        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;
+    }
+
+    /*
+     * Private remove method that skips bounds checking and does not
+     * return the value removed.
+     */
+    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
+    }
+```
\ No newline at end of file
diff --git "a/second/week_01/89/HashMap\346\272\220\347\240\201\345\210\206\346\236\220.md" "b/second/week_01/89/HashMap\346\272\220\347\240\201\345\210\206\346\236\220.md"
new file mode 100644
index 0000000..36acca9
--- /dev/null
+++ "b/second/week_01/89/HashMap\346\272\220\347\240\201\345\210\206\346\236\220.md"
@@ -0,0 +1,125 @@
+#HashMap
+
+## 总体概述
+
+HashMap是基于哈希表的Map接口实现，提供key-valus的映射集合。内部数组+链表/红黑树结构组成，提供高效的查询、插入与删除操作。
+
+## 成员变量
+
+- static final int DEFAULT_INITIAL_CAPACITY = 1 << 4; // 默认初始容量16
+ 
+- static final int MAXIMUM_CAPACITY = 1 << 30;//最大的容量为2的30次方
+ 
+- static final float DEFAULT_LOAD_FACTOR = 0.75f;//默认装载因子
+
+static final int TREEIFY_THRESHOLD = 8;//桶大于8时树化
+
+## 构造方法
+
+```java
+    public HashMap(int initialCapacity) {
+        this(initialCapacity, DEFAULT_LOAD_FACTOR);
+    }
+    
+    public HashMap(int initialCapacity, float loadFactor) {
+        if (initialCapacity < 0)
+            throw new IllegalArgumentException("Illegal initial capacity: " +
+                                               initialCapacity);
+        if (initialCapacity > MAXIMUM_CAPACITY)
+            initialCapacity = MAXIMUM_CAPACITY;
+        if (loadFactor <= 0 || Float.isNaN(loadFactor))
+            throw new IllegalArgumentException("Illegal load factor: " +
+                                               loadFactor);
+        this.loadFactor = loadFactor;
+        this.threshold = tableSizeFor(initialCapacity);
+    }
+    
+    //将容量改为离cap最近的2的倍数的值，hash时能均匀的分布到各个桶中
+    static final int tableSizeFor(int cap) {
+        int n = cap - 1;
+        n |= n >>> 1;
+        n |= n >>> 2;
+        n |= n >>> 4;
+        n |= n >>> 8;
+        n |= n >>> 16;
+        return (n < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1;
+    }
+```
+
+## put
+```java
+    public V put(K key, V value) {
+        return putVal(hash(key), key, value, false, true);
+    }
+    
+    final V putVal(int hash, K key, V value, boolean onlyIfAbsent,
+                   boolean evict) {
+        Node<K,V>[] tab; Node<K,V> p; int n, i;
+        if ((tab = table) == null || (n = tab.length) == 0)
+            n = (tab = resize()).length;
+        if ((p = tab[i = (n - 1) & hash]) == null)
+            tab[i] = newNode(hash, key, value, null);
+        else {
+            Node<K,V> e; K k;
+            if (p.hash == hash &&
+                ((k = p.key) == key || (key != null && key.equals(k))))
+                e = p;
+            else if (p instanceof TreeNode)
+                e = ((TreeNode<K,V>)p).putTreeVal(this, tab, hash, key, value);
+            else {
+                for (int binCount = 0; ; ++binCount) {
+                    if ((e = p.next) == null) {
+                        p.next = newNode(hash, key, value, null);
+                        if (binCount >= TREEIFY_THRESHOLD - 1) // -1 for 1st
+                            treeifyBin(tab, hash);
+                        break;
+                    }
+                    if (e.hash == hash &&
+                        ((k = e.key) == key || (key != null && key.equals(k))))
+                        break;
+                    p = e;
+                }
+            }
+            if (e != null) { // existing mapping for key
+                V oldValue = e.value;
+                if (!onlyIfAbsent || oldValue == null)
+                    e.value = value;
+                afterNodeAccess(e);
+                return oldValue;
+            }
+        }
+        ++modCount;
+        if (++size > threshold)
+            resize();
+        afterNodeInsertion(evict);
+        return null;
+    }
+```     
+
+## get
+```java
+    public V get(Object key) {
+        Node<K,V> e;
+        return (e = getNode(hash(key), key)) == null ? null : e.value;
+    }
+    
+    final Node<K,V> getNode(int hash, Object key) {
+        Node<K,V>[] tab; Node<K,V> first, e; int n; K k;
+        if ((tab = table) != null && (n = tab.length) > 0 &&
+            (first = tab[(n - 1) & hash]) != null) {
+            if (first.hash == hash && // always check first node
+                ((k = first.key) == key || (key != null && key.equals(k))))
+                return first;
+            if ((e = first.next) != null) {
+                if (first instanceof TreeNode)
+                    return ((TreeNode<K,V>)first).getTreeNode(hash, key);
+                do {
+                    if (e.hash == hash &&
+                        ((k = e.key) == key || (key != null && key.equals(k))))
+                        return e;
+                } while ((e = e.next) != null);
+            }
+        }
+        return null;
+    }
+```  
\ No newline at end of file
diff --git "a/second/week_01/89/LinkedList\346\272\220\347\240\201\345\210\206\346\236\220.md" "b/second/week_01/89/LinkedList\346\272\220\347\240\201\345\210\206\346\236\220.md"
new file mode 100644
index 0000000..5906f76
--- /dev/null
+++ "b/second/week_01/89/LinkedList\346\272\220\347\240\201\345\210\206\346\236\220.md"
@@ -0,0 +1,114 @@
+# LinkedList 源码分析
+
+
+## 总体概述
+LinkedList是动态数组的另一种实现。基础层基于双向循环链表。它的优点是它可以快速删除和添加元素，而无需移动诸如ArrayList之类的许多元素，但是它需要一个遍历链接列表。元素是匹配的。因此，LinkedList适用于频繁删除和添加元素且发现元素较少的场景。
+
+## 成员变量
+
+- transient int size = 0;
+
+    
+- transient Node<E> first;//头结点
+
+    
+- transient Node<E> last;//尾结点
+
+## 构造方法
+
+```java
+
+    //双向链表
+    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;
+        }
+    }
+```
+
+
+## linkBefore 插入
+
+```java
+ void linkBefore(E e, Node<E> succ) {
+        // assert succ != null;
+        //首先获取succ节点的上一个节点pred
+        final Node<E> pred = succ.prev;
+        //新建一个e节点，e的上一个截点为pred，e的下一个节点为succ
+        final Node<E> newNode = new Node<>(pred, e, succ);
+        succ.prev = newNode;
+        //pred为null，succ就是头结点
+        if (pred == null)
+            first = newNode;
+        else
+            pred.next = newNode;
+        size++;
+        modCount++;
+    }
+```
+
+## unlink 删除
+
+```java
+E unlink(Node<E> x) {
+        // assert x != null;
+        //获取已删除节点的上一个节点和下一个节点
+        final E element = x.item;
+        final Node<E> next = x.next;
+        final Node<E> prev = x.prev;
+        
+        
+        if (prev == null) {
+            //头指针指向下一个节点
+            first = next;
+        } else {
+            //下一个节点的下一个指向下一个节点的下一个，而当前节点的上一个分配为null
+            prev.next = next;
+            x.prev = null;
+        }
+        
+        if (next == null) {
+            //尾指针指向上一个节点
+            last = prev;
+        } else {
+            //下一个节点的上一个指向前一个节点，并且当前节点的下一个节点被分配为空
+            next.prev = prev;
+            x.next = null;
+        }
+
+        x.item = null;
+        size--;
+        modCount++;
+        return element;
+    }
+```
+
+## get
+
+```java
+public E get(int index) {
+           checkElementIndex(index);
+           //遍历获取index对应的item
+           return node(index).item;
+       }
+```       
+
+## set
+```java
+public E set(int index, E element) {
+        checkElementIndex(index);
+        //遍历获取index对应的node
+        Node<E> x = node(index);
+        //获取oldval
+        E oldVal = x.item;
+        //node的item设置为element
+        x.item = element;
+        return oldVal;
+    }
+```    
\ No newline at end of file
-- 
Gitee


From cdcb2f856496be56318026a68966a7d1cd4a16af Mon Sep 17 00:00:00 2001
From: simpleman594 <wlkybg@163.com>
Date: Mon, 9 Mar 2020 00:02:58 +0800
Subject: [PATCH 2/2] =?UTF-8?q?89=E6=BA=90=E7=A0=81=E5=88=86=E6=9E=90?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 ...hMap\346\272\220\347\240\201\345\210\206\346\236\220.md" | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git "a/second/week_01/89/HashMap\346\272\220\347\240\201\345\210\206\346\236\220.md" "b/second/week_01/89/HashMap\346\272\220\347\240\201\345\210\206\346\236\220.md"
index 36acca9..b00181a 100644
--- "a/second/week_01/89/HashMap\346\272\220\347\240\201\345\210\206\346\236\220.md"
+++ "b/second/week_01/89/HashMap\346\272\220\347\240\201\345\210\206\346\236\220.md"
@@ -56,21 +56,27 @@ static final int TREEIFY_THRESHOLD = 8;//桶大于8时树化
                    boolean evict) {
         Node<K,V>[] tab; Node<K,V> p; int n, i;
         if ((tab = table) == null || (n = tab.length) == 0)
+            //利用resize生成对应的tab[]数组
             n = (tab = resize()).length;
         if ((p = tab[i = (n - 1) & hash]) == null)
+            //桶内没有元素，直接插入
             tab[i] = newNode(hash, key, value, null);
         else {
             Node<K,V> e; K k;
+            //桶内第一个元素的key等于待放入的key
             if (p.hash == hash &&
                 ((k = p.key) == key || (key != null && key.equals(k))))
                 e = p;
             else if (p instanceof TreeNode)
+                //已经树化
                 e = ((TreeNode<K,V>)p).putTreeVal(this, tab, hash, key, value);
             else {
+                
                 for (int binCount = 0; ; ++binCount) {
                     if ((e = p.next) == null) {
                         p.next = newNode(hash, key, value, null);
                         if (binCount >= TREEIFY_THRESHOLD - 1) // -1 for 1st
+                            //树化
                             treeifyBin(tab, hash);
                         break;
                     }
-- 
Gitee