From 45f970eb65e7934935871d03d5508e12130a8dfc Mon Sep 17 00:00:00 2001
From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com>
Date: Wed, 12 May 2021 20:49:36 +0800
Subject: [PATCH] =?UTF-8?q?Update=200707.=E8=AE=BE=E8=AE=A1=E9=93=BE?=
 =?UTF-8?q?=E8=A1=A8.md?=
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---
 problems/0707.设计链表.md | 71 +++++++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)

diff --git a/problems/0707.设计链表.md b/problems/0707.设计链表.md
index f98051c9..93133b55 100644
--- a/problems/0707.设计链表.md
+++ b/problems/0707.设计链表.md
@@ -157,7 +157,78 @@ private:
 
 
 Java：
+```Java
+class MyLinkedList {
+    //size存储链表元素的个数
+    int size;
+    //虚拟头结点
+    ListNode head;
 
+    //初始化链表
+    public MyLinkedList() {
+        size = 0;
+        head = new ListNode(0);
+    }
+
+    //获取第index个节点的数值
+    public int get(int index) {
+        //如果index非法，返回-1
+        if (index < 0 || index >= size) {
+            return -1;
+        }
+        ListNode currentNode = head;
+        //包含一个虚拟头节点，所以查找第 index+1 个节点
+        for (int i = 0; i <= index; i++) {
+            currentNode = currentNode.next;
+        }
+        return currentNode.val;
+    }
+
+    //在链表最前面插入一个节点
+    public void addAtHead(int val) {
+        addAtIndex(0, val);
+    }
+
+    //在链表的最后插入一个节点
+    public void addAtTail(int val) {
+        addAtIndex(size, val);
+    }
+
+    // 在第 index 个节点之前插入一个新节点，例如index为0，那么新插入的节点为链表的新头节点。
+    // 如果 index 等于链表的长度，则说明是新插入的节点为链表的尾结点
+    // 如果 index 大于链表的长度，则返回空
+    public void addAtIndex(int index, int val) {
+        if (index > size) {
+            return;
+        }
+        if (index < 0) {
+            index = 0;
+        }
+        size++;
+        //找到要插入节点的前驱
+        ListNode pred = head;
+        for (int i = 0; i < index; i++) {
+            pred = pred.next;
+        }
+        ListNode toAdd = new ListNode(val);
+        toAdd.next = pred.next;
+        pred.next = toAdd;
+    }
+
+    //删除第index个节点
+    public void deleteAtIndex(int index) {
+        if (index < 0 || index >= size) {
+            return;
+        }
+        size--;
+        ListNode pred = head;
+        for (int i = 0; i < index; i++) {
+            pred = pred.next;
+        }
+        pred.next = pred.next.next;
+    }
+}
+```
 
 Python：