diff --git a/.idea/.gitignore b/.idea/.gitignore
new file mode 100644
index 0000000000000000000000000000000000000000..26d33521af10bcc7fd8cea344038eaaeb78d0ef5
--- /dev/null
+++ b/.idea/.gitignore
@@ -0,0 +1,3 @@
+# Default ignored files
+/shelf/
+/workspace.xml
diff --git a/.idea/misc.xml b/.idea/misc.xml
new file mode 100644
index 0000000000000000000000000000000000000000..e208459b8afde5f7980720efd6bbb97f7ae24541
--- /dev/null
+++ b/.idea/misc.xml
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_8" project-jdk-name="1.8" project-jdk-type="JavaSDK">
+    <output url="file://$PROJECT_DIR$/out" />
+  </component>
+</project>
\ No newline at end of file
diff --git a/.idea/modules.xml b/.idea/modules.xml
new file mode 100644
index 0000000000000000000000000000000000000000..a9a967ebf636c25d481adbb480e9fb8fb3f25eb1
--- /dev/null
+++ b/.idea/modules.xml
@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ProjectModuleManager">
+    <modules>
+      <module fileurl="file://$PROJECT_DIR$/lec02-linkedlist.iml" filepath="$PROJECT_DIR$/lec02-linkedlist.iml" />
+    </modules>
+  </component>
+</project>
\ No newline at end of file
diff --git a/.idea/vcs.xml b/.idea/vcs.xml
new file mode 100644
index 0000000000000000000000000000000000000000..35eb1ddfbbc029bcab630581847471d7f238ec53
--- /dev/null
+++ b/.idea/vcs.xml
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="" vcs="Git" />
+  </component>
+</project>
\ No newline at end of file
diff --git a/LinkList1.java b/LinkList1.java
new file mode 100644
index 0000000000000000000000000000000000000000..c5087c317646d04d75adedd6568a8c86506cd7e2
--- /dev/null
+++ b/LinkList1.java
@@ -0,0 +1,86 @@
+package com.company;
+
+public class LinkList1<E> {
+    public MyNode headnode;
+
+    public LinkList1() {
+        this.headnode = null;
+    }
+
+    public void addToFront(E value) {
+        if (headnode == null) {
+            this.headnode = new MyNode(value);
+        } else {
+            MyNode step = headnode;
+            step.next = headnode.next;
+            this.headnode = new MyNode(value);
+            this.headnode.next = step;
+        }
+    }
+
+    public void addToRear(E value) {
+        if (headnode == null) {
+            this.headnode = new MyNode(value);
+        } else {
+            MyNode node = headnode;
+            while (node.next != null) {
+                node = node.next;
+            }
+            node.next = new MyNode(value);
+        }
+    }
+
+    public void printItems() {
+        MyNode node = this.headnode;
+        if (node == null) {
+            System.out.println("soory,No String");
+        } else {
+            while (node != null) {
+                System.out.printf(node.item + "->");
+                node = node.next;
+            }
+        }
+    }
+
+    public void deleteItems(String value) {
+        MyNode node = headnode;
+        if (node != null) {
+            if (node.item.equals(value)) {
+                headnode = node.next;
+                return;
+            } else {
+                while (node.next != null) {
+                    if (node.next.item.equals(value)) {
+                        node.next = node.next.next;
+                        return;
+                    }
+                    node = node.next;
+                }
+            }
+        }
+    }
+
+    public boolean findItem(String value) {
+        MyNode node = headnode;
+        while (node != null) {
+            if (node.item.equals(value)) {
+                return true;
+            } else {
+                node = node.next;
+            }
+        }
+        return false;
+    }
+
+    public void size() {
+        int num = 0;
+        MyNode node = headnode;
+        while (node != null) {
+            num++;
+            node = node.next;
+        }
+        System.out.println("链表长度为:" + num);
+    }
+}
+
+
diff --git a/LinkList2.java b/LinkList2.java
new file mode 100644
index 0000000000000000000000000000000000000000..72eee86046021ce872c7d30c2c9a4964e7eb1bfb
--- /dev/null
+++ b/LinkList2.java
@@ -0,0 +1,101 @@
+package com.company;
+
+public class LinkList2<E> {
+    public MyNode head;
+    public MyNode tail;
+
+
+    public LinkList2() {
+        this.head = null;
+        this.tail = null;
+
+    }
+
+    public void addToFront(E value) {
+        if (head == null) {
+            this.head = new MyNode(value);
+            this.tail = head;
+        } else {
+            MyNode step = head;
+            step.next = head.next;
+            this.head = new MyNode(value);
+            this.head.next = step;
+        }
+    }
+
+    public void addToRear(E value) {
+        if (head == null) {
+            this.head = new MyNode(value);
+            this.tail = head;
+        } else {
+            /*第一种方法*/
+//            MyNode node = head;
+//            while (node.next != null) {
+//                node = node.next;
+//            }
+//            node.next = new MyNode(value);
+//            tail = node.next;
+            /*第二种方法*/
+            MyNode node = this.tail;
+            node.next = new MyNode(value);
+            tail = node.next;
+        }
+    }
+
+    public void printItems() {
+        MyNode node = this.head;
+        if (node == null) {
+            System.out.println("soory,No String");
+        } else {
+            while (node != null) {
+                System.out.printf(node.item + "->");
+                node = node.next;
+            }
+        }
+    }
+
+    public void deleteItems(String value) {
+        MyNode node = head;
+        if (node != null) {
+            if (node.item.equals(value)) {
+                head = node.next;
+                return;
+            } else {
+                while (node.next != null) {
+                    if (node.next.item.equals(value)) {
+                        if (node.next.next == null) {
+                            this.tail = node;
+                        }
+                        node.next = node.next.next;
+                        return;
+                    }
+                    node = node.next;
+                }
+            }
+        }
+    }
+
+    public boolean findItem(String value) {
+        MyNode node = head;
+        while (node != null) {
+            if (node.item.equals(value)) {
+                return true;
+            } else {
+                node = node.next;
+            }
+        }
+        return false;
+    }
+
+    public void size() {
+        int num = 0;
+        MyNode node = head;
+        while (node != null) {
+            num++;
+            node = node.next;
+        }
+        System.out.println("链表长度为:" + num);
+    }
+}
+
+
diff --git a/LinkList3.java b/LinkList3.java
new file mode 100644
index 0000000000000000000000000000000000000000..512000eda2744f0fd037da6bd0b64bb8c9acc1ab
--- /dev/null
+++ b/LinkList3.java
@@ -0,0 +1,102 @@
+package com.company;
+
+public class LinkList3<E> {
+    public MyNode headnode;
+
+    public LinkList3() {
+        this.headnode = null;
+    }
+
+    public void addToFront(E value) {
+        if (headnode == null) {
+            this.headnode = new MyNode(value);
+            headnode.prev = null;
+            headnode.next = null;
+        } else {
+            MyNode temp = headnode;
+            MyNode newnode = new MyNode(value);
+            temp.prev = newnode;
+            newnode.next = temp;
+            headnode = newnode;
+        }
+    }
+
+    public void addToRear(E value) {
+        MyNode newnode = new MyNode(value);
+        if (headnode == null) {
+            this.headnode = new MyNode(value);
+            headnode.next = null;
+            headnode.prev = null;
+        } else {
+            MyNode node = headnode;
+            while (node.next != null) {
+                node = node.next;
+            }
+            node.next = newnode;
+            node.next.prev = node;
+        }
+    }
+
+    public void printItems() {
+        MyNode node = this.headnode;
+        if (node == null) {
+            System.out.println("soory,No String");
+        } else {
+            while (node != null) {
+                System.out.printf(node.item + "->");
+                node = node.next;
+            }
+        }
+    }
+
+    public void deleteItems(String value) {
+        MyNode node = headnode;
+        if (node != null) {
+            if (node.item.equals(value)) {
+                node = node.next;
+                node.prev = null;
+                headnode = node;
+                return;
+            }
+            node = node.next;
+            while (node != null) {
+                if (node.item.equals(value) && node.next != null) {
+                    MyNode myNode = node.next;
+                    myNode.prev = node.prev;
+                    node.prev.next = myNode;
+                    return;
+                } else if (node.item.equals(value) && node.next == null) {
+                    node.prev.next = null;
+                    return;
+                } else {
+                    node = node.next;
+                }
+            }
+            System.out.println("元素不在链表中");
+        }
+    }
+
+    public boolean findItem(String value) {
+        MyNode node = headnode;
+        while (node != null) {
+            if (node.item.equals(value)) {
+                return true;
+            } else {
+                node = node.next;
+            }
+        }
+        return false;
+    }
+
+    public void size() {
+        int num = 0;
+        MyNode node = headnode;
+        while (node != null) {
+            num++;
+            node = node.next;
+        }
+        System.out.println("链表长度为:" + num);
+    }
+}
+
+
diff --git a/MyMain.java b/MyMain.java
new file mode 100644
index 0000000000000000000000000000000000000000..1726740c8f9cf99d199781dc4cda620bb17442ef
--- /dev/null
+++ b/MyMain.java
@@ -0,0 +1,40 @@
+package com.company;
+
+
+public class MyMain {
+    public static void main(String[] args) {
+        /*作业1*/
+        LinkList1<String> lIst1Link = new LinkList1<>();
+        lIst1Link.addToRear("a");
+        lIst1Link.addToRear("b");
+        lIst1Link.addToFront("c");
+        lIst1Link.addToRear("d");
+        lIst1Link.deleteItems("d");
+        System.out.println(lIst1Link.findItem("b"));
+        lIst1Link.size();
+        lIst1Link.printItems();
+
+        /*作业2*/
+        LinkList2<String> linkList2 = new LinkList2<>();
+        linkList2.addToRear("c");
+        linkList2.addToFront("a");
+        linkList2.addToFront("b");
+        linkList2.printItems();
+        linkList2.deleteItems("c");
+        linkList2.size();
+        System.out.println(linkList2.findItem("a"));
+
+        /*作业3*/
+        LinkList3 linkList3 = new LinkList3();
+        linkList3.addToFront("b");
+        linkList3.addToFront("a");
+        linkList3.addToRear("d");
+        linkList3.addToRear("p");
+        linkList3.printItems();
+        System.out.println('\n');
+        linkList3.deleteItems("d");
+        System.out.println(linkList3.findItem("2"));
+        linkList3.printItems();
+        linkList3.size();
+    }
+}
diff --git a/MyNode.java b/MyNode.java
new file mode 100644
index 0000000000000000000000000000000000000000..ef6948cae6ef6d5e3c19cf71546915a182f13481
--- /dev/null
+++ b/MyNode.java
@@ -0,0 +1,10 @@
+package com.company;
+
+public class MyNode<E> {
+    E item;
+    MyNode next=null;
+    public MyNode prev;
+    public MyNode(E item) {
+        this.item = item;
+    }
+}
diff --git a/Node.java b/Node.java
deleted file mode 100644
index ed7a3524e3c608d2a479f484e240452ad34c5a51..0000000000000000000000000000000000000000
--- a/Node.java
+++ /dev/null
@@ -1,8 +0,0 @@
-public class Node<E> {
-    E item;
-    Node<E> next = null;
-
-    Node(E item) {
-        this.item = item;
-    }
-}
\ No newline at end of file
diff --git a/lec02-linkedlist.iml b/lec02-linkedlist.iml
new file mode 100644
index 0000000000000000000000000000000000000000..b107a2dd81165eaaf682ad3da030668b937fbb6c
--- /dev/null
+++ b/lec02-linkedlist.iml
@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager" inherit-compiler-output="true">
+    <exclude-output />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$" isTestSource="false" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+  </component>
+</module>
\ No newline at end of file