<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-mail</artifactId>
</dependency>

server:
  port: 8887

spring:
  mail:
    host: smtp.163.com
    username: ffj0721@163.com
    password: xxxx # 授权码
    protocol: smtp
    properties.mail.smtp.auth: true
    properties.mail.smtp.port: 994
    properties.mail.display.sendmail: DoubleFJ
    properties.mail.display.sendname: Spring Boot Email
    properties.mail.smtp.starttls.enable: true
    properties.mail.smtp.starttls.required: true
    properties.mail.smtp.ssl.enable: true
    default-encoding: utf-8
    from: ffj0721@163.com

package com.example.springbootmail.service;
import javax.mail.MessagingException;

/**
 * 常用邮件接口
 */
public interface IMailService {
    /**
     * 发送文本邮件
     * @param to
     * @param subject
     * @param content
     */
    public void sendSimpleMail(String to, String subject, String content);

    public void sendSimpleMail(String to, String subject, String content, String... cc);

    /**
     * 发送HTML邮件
     * @param to
     * @param subject
     * @param content
     * @throws MessagingException
     */
    public void sendHtmlMail(String to, String subject, String content) throws MessagingException;

    public void sendHtmlMail(String to, String subject, String content, String... cc);

    /**
     * 发送带附件的邮件
     * @param to
     * @param subject
     * @param content
     * @param filePath
     * @throws MessagingException
     */
    public void sendAttachmentsMail(String to, String subject, String content, String filePath) throws MessagingException;

    public void sendAttachmentsMail(String to, String subject, String content, String filePath, String... cc);

    /**
     * 发送正文中有静态资源的邮件
     * @param to
     * @param subject
     * @param content
     * @param rscPath
     * @param rscId
     * @throws MessagingException
     */
    public void sendResourceMail(String to, String subject, String content, String rscPath, String rscId) throws MessagingException;

    public void sendResourceMail(String to, String subject, String content, String rscPath, String rscId, String... cc);

}

/**
 * 发送邮件实现类
 */
@Service
public class IMailServiceImpl implements IMailService {

    @Autowired
    private JavaMailSender mailSender;

    @Value("${spring.mail.from}")
    private String from;

/**
  * 发送文本邮件
  *
  * @param to
  *          邮件接收方
  * @param subject
  *          邮件标题
  * @param content
  *          邮件内容
  */
 @Override
 public void sendSimpleMail(String to, String subject, String content) {
     SimpleMailMessage message = new SimpleMailMessage();
     message.setFrom(from);
     message.setTo(to);
     message.setSubject(subject);
     message.setText(content);
     mailSender.send(message);
 }

 /**
  *
  * @param to
  *          邮件接收方
  * @param subject
  *          邮件标题
  * @param content
  *          邮件内容
  * @param cc
  *          抄送方
  */
 @Override
 public void sendSimpleMail(String to, String subject, String content, String... cc) {
     SimpleMailMessage message = new SimpleMailMessage();
     message.setFrom(from);
     message.setTo(to);
     message.setCc(cc);
     message.setSubject(subject);
     message.setText(content);
     mailSender.send(message);
 }

/**
     * 发送 HTML 邮件
     *
     * @param to
     * @param subject
     * @param content
     */
    @Override
    public void sendHtmlMail(String to, String subject, String content) throws MessagingException {
        MimeMessage message = mailSender.createMimeMessage();

        // true 表示需要创建一个multipart message
        MimeMessageHelper helper = new MimeMessageHelper(message, true);
        helper.setFrom(from);
        helper.setTo(to);
        helper.setSubject(subject);
        helper.setText(content, true);

        mailSender.send(message);
    }

/**
 * 发送带附件的邮件
 *
 * @param to
 * @param subject
 * @param content
 * @param filePath
 */
public void sendAttachmentsMail(String to, String subject, String content, String filePath) throws MessagingException {
    MimeMessage message = mailSender.createMimeMessage();

    MimeMessageHelper helper = new MimeMessageHelper(message, true);
    helper.setFrom(from);
    helper.setTo(to);
    helper.setSubject(subject);
    helper.setText(content, true);

    FileSystemResource file = new FileSystemResource(new File(filePath));
    // 截取附件名
    String fileName = filePath.substring(filePath.lastIndexOf("/") + 1);
    helper.addAttachment(fileName, file);

    mailSender.send(message);
}

/**
 * 发送正文中有静态资源（图片）的邮件
 *
 * @param to
 * @param subject
 * @param content
 * @param rscPath
 * @param rscId
 */
public void sendResourceMail(String to, String subject, String content, String rscPath, String rscId) throws MessagingException {
    MimeMessage message = mailSender.createMimeMessage();

    MimeMessageHelper helper = new MimeMessageHelper(message, true);
    helper.setFrom(from);
    helper.setTo(to);
    helper.setSubject(subject);
    helper.setText(content, true);

    FileSystemResource res = new FileSystemResource(new File(rscPath));
    helper.addInline(rscId, res);

    mailSender.send(message);
}

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>spring-boot-mail test</title>
    <style>
        body {
            text-align: center;
            margin-left: auto;
            margin-right: auto;
        }
        #welcome {
            text-align: center;
        }
    </style>
</head>
<body>
<div id="welcome">
    <h3>Welcome To My Friend!</h3>

    GitHub：
        <a href="#" th:href="@{${github_url}}" target="_bank">
            <strong>GitHub</strong>
        </a>
    <br />
    <br />
    个人博客：
        <a href="#" th:href="@{${blog_url}}" target="_bank">
            <strong>DoubleFJ の Blog</strong>
        </a>
    <br />
    <br />
    <img width="258px" height="258px"
         src="https://raw.githubusercontent.com/Folgerjun/materials/master/blog/img/WC-GZH.jpg">
    <br />微信公众号（诗词鉴赏）
</div>
</body>
</html>

package com.example.springbootmail.controller;

import com.example.springbootmail.service.impl.IMailServiceImpl;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.thymeleaf.TemplateEngine;
import org.thymeleaf.context.Context;

@RestController
@RequestMapping("/Mail")
public class MailController {

    private static final String SUCC_MAIL = "邮件发送成功！";
    private static final String FAIL_MAIL = "邮件发送失败！";

    // 图片路径
    private static final String IMG_PATH = "C:/Users/zjj/Desktop/github/materials/blog/img/WC-GZH.jpg";
    // 发送对象
    private static final String MAIL_TO = "folgerjun@gmail.com";

    @Autowired
    private IMailServiceImpl mailService;
    @Autowired
    private TemplateEngine templateEngine;

    @RequestMapping("/Email")
    public String index(){
        try {
            mailService.sendSimpleMail(MAIL_TO,"这是一封普通的邮件","这是一封普通的SpringBoot测试邮件");
        }catch (Exception ex){
            ex.printStackTrace();
            return FAIL_MAIL;
        }
        return SUCC_MAIL;
    }

    @RequestMapping("/htmlEmail")
    public String htmlEmail(){
        try {
            mailService.sendHtmlMail(MAIL_TO,"这是一HTML的邮件","<body>\n" +
                    "<div id=\"welcome\">\n" +
                    "    <h3>Welcome To My Friend!</h3>\n" +
                    "\n" +
                    "    GitHub：\n" +
                    "        <a href=\"#\" th:href=\"@{${github_url}}\" target=\"_bank\">\n" +
                    "            <strong>GitHub</strong>\n" +
                    "        </a>\n" +
                    "    <br />\n" +
                    "    <br />\n" +
                    "    个人博客：\n" +
                    "        <a href=\"#\" th:href=\"@{${blog_url}}\" target=\"_bank\">\n" +
                    "            <strong>DoubleFJ の Blog</strong>\n" +
                    "        </a>\n" +
                    "    <br />\n" +
                    "    <br />\n" +
                    "    <img width=\"258px\" height=\"258px\"\n" +
                    "         src=\"https://raw.githubusercontent.com/Folgerjun/materials/master/blog/img/WC-GZH.jpg\">\n" +
                    "    <br />微信公众号（诗词鉴赏）\n" +
                    "</div>\n" +
                    "</body>");
        }catch (Exception ex){
            ex.printStackTrace();
            return FAIL_MAIL;
        }
        return SUCC_MAIL;
    }

    @RequestMapping("/attachmentsMail")
    public String attachmentsMail(){
        try {
            mailService.sendAttachmentsMail(MAIL_TO, "这是一封带附件的邮件", "邮件中有附件，请注意查收！", IMG_PATH);
        }catch (Exception ex){
            ex.printStackTrace();
            return FAIL_MAIL;
        }
        return SUCC_MAIL;
    }

    @RequestMapping("/resourceMail")
    public String resourceMail(){
        try {
            String rscId = "DoubleFJ";
            String content = "<html><body>这是有图片的邮件<br/><img src=\'cid:" + rscId + "\' ></body></html>";
            mailService.sendResourceMail(MAIL_TO, "这邮件中含有图片", content, IMG_PATH, rscId);

        }catch (Exception ex){
            ex.printStackTrace();
            return FAIL_MAIL;
        }
        return SUCC_MAIL;
    }

    @RequestMapping("/templateMail")
    public String templateMail(){
        try {
            Context context = new Context();
            context.setVariable("github_url", "https://github.com/Folgerjun");
            context.setVariable("blog_url", "http://putop.top/");
            String emailContent = templateEngine.process("mailTemplate", context);

            mailService.sendHtmlMail(MAIL_TO, "这是模板邮件", emailContent);
        }catch (Exception ex){
            ex.printStackTrace();
            return FAIL_MAIL;
        }
        return SUCC_MAIL;
    }
}

在歌曲列表中，第 i 首歌曲的持续时间为 time[i] 秒。

返回其总持续时间（以秒为单位）可被 60 整除的歌曲对的数量。形式上，我们希望索引的数字  i < j 且有 (time[i] + time[j]) % 60 == 0。

示例 1：
输入：[30,20,150,100,40]
输出：3
解释：这三对的总持续时间可被 60 整数：
(time[0] = 30, time[2] = 150): 总持续时间 180
(time[1] = 20, time[3] = 100): 总持续时间 120
(time[1] = 20, time[4] = 40): 总持续时间 60

示例 2：
输入：[60,60,60]
输出：3
解释：所有三对的总持续时间都是 120，可以被 60 整数。
 
提示：

1 <= time.length <= 60000
1 <= time[i] <= 500

/**
 * 超时
 * 
 * @param time
 * @return
 */
public int numPairsDivisibleBy60(int[] time) {
    int result = 0;
    for (int i = 0; i < time.length - 1; i++) {
        for (int j = i + 1; j < time.length; j++) {
            int value = (time[i] + time[j]) % 60;
            if (value == 0)
                result++;
        }
    }
    return result;
}

public int numPairsDivisibleBy601(int[] time) {
    // 每个元素取60余
    time = Arrays.stream(time).map(x -> x % 60).toArray();
    int[] arrCount = new int[60];
    // 统计对应下标数
    Arrays.stream(time).forEach(x -> {
        arrCount[x]++;
    });
    // 余数是 0 或 30 的两两配对
    int result = qiuhe(arrCount[0]) + qiuhe(arrCount[30]);
    // 其余互相配对
    for (int i = 1; i < 30; i++) {
        int count1 = arrCount[i];
        int count2 = arrCount[60 - i];
        result += count1 * count2;
    }
    return result;
}

/**
 * 求两两配对数
 * 
 * @param num
 * @return
 */
private int qiuhe(int num) {
    if (num < 2)
        return 0;
    // (num-1)!
    return num * (num - 1) / 2;
}

public int numPairsDivisibleBy602(int[] time) {
    int result = 0;
    int[] arrCount = new int[60];
    for (int t : time) {
        // 对应的下标
        int index = t == 0 ? 0 : 60 - t % 60;
        // 与已经统计的数进行匹配 可防止两两重复匹配
        result += arrCount[index];
        // 对应数字加一
        arrCount[t % 60]++;
    }
    return result;
}

// 常见参数
-Xms1024m 初始堆大小 
-Xmx1024m 最大堆大小  一般将 Xms 和 Xmx 设置为相同大小，防止堆扩展，影响性能。
-XX:NewSize=n:设置年轻代大小 
-XX:NewRatio=n:设置年轻代和年老代的比值.如:为 3,表示年轻代与年老代比值为 1:3,年轻代占整个年轻代年老代和的 1/4 
-XX:SurvivorRatio=n:年轻代中 Eden 区与两个 Survivor 区的比值.注意 Survivor 区有两个.如: 3,表示 Eden:Survivor=3:2,一个 Survivor 区占整个年轻代的 1/5 
-XX:MaxPermSize=n:设置持久代大小
-XX:+HeapDumpOnOutOfMemoryError OOM 时自动保存堆文件，可以用 visualvm 分析堆文件

// 收集器设置 
-XX:+UseSerialGC:设置串行收集器
-XX:+UseParallelGC:设置并行收集器
-XX:+UseParalledlOldGC:设置并行年老代收集器
-XX:+UseConcMarkSweepGC:设置并发收集器

// 垃圾回收统计信息
-XX:+PrintGC 
-XX:+PrintGCDetails 
-XX:+PrintGCTimeStamps 
-Xloggc:filename

// 并行收集器设置 
-XX:ParallelGCThreads=n:设置并行收集器收集时使用的CPU数 
-XX:MaxGCPauseMillis=n:设置并行收集最大暂停时间 
-XX:GCTimeRatio=n:设置垃圾回收时间占程序运行时间的百分比.公式为 1/(1+n)

// 并发收集器设置 
-XX:+CMSIncrementalMode:设置为增量模式.适用于单 CPU 情况. 
-XX:ParallelGCThreads=n:设置并发收集器年轻代收集方式为并行收集时,使用的 CPU 数.并行收集线程数.

反转一个单链表。

示例:
输入: 1->2->3->4->5->NULL
输出: 5->4->3->2->1->NULL

进阶:
你可以迭代或递归地反转链表。你能否用两种方法解决这道题？

public class ReverseLinkedList {

    public class ListNode {
        int val;
        ListNode next;

        ListNode(int x) {
            val = x;
        }
    }

    /**
     * 递归
     * 
     * @param head
     * @return
     */
    public ListNode reverseList(ListNode head) {
        ListNode reverseList = null;
        return helper(head, reverseList);
    }

    private ListNode helper(ListNode head, ListNode reverseList) {
        if (head == null) // 反转结束
            return reverseList;
        // 节点指针变换
        ListNode tempNode = head.next;
        head.next = reverseList;
        return helper(tempNode, head);
    }

    /**
     * 迭代
     * 
     * @param head
     * @return
     */
    public ListNode reverseList1(ListNode head) {

        ListNode newHead = null;
        while (head != null) { // 遍历
            ListNode next = head.next;
            head.next = newHead;
            newHead = head;
            head = next;
        }
        return newHead;
    }
}

反转从位置 m 到 n 的链表。请使用一趟扫描完成反转。

说明:
1 ≤ m ≤ n ≤ 链表长度。

示例:

输入: 1->2->3->4->5->NULL, m = 2, n = 4
输出: 1->4->3->2->5->NULL

public class ReverseLinkedListII {

    public class ListNode {
        int val;
        ListNode next;

        ListNode(int x) {
            val = x;
        }
    }

    public ListNode reverseBetween(ListNode head, int m, int n) {
        if (head == null)
            return null;
        // 新建一个节点并指向 head
        ListNode dummy = new ListNode(0);
        dummy.next = head;
        ListNode pre = dummy;
        // pre 为需要反转的前节点
        for (int i = 0; i < m - 1; i++)
            pre = pre.next;

        // 需要反转的节点 双指针
        ListNode start = pre.next;
        ListNode then = start.next;

        // 反转节点
        for (int i = 0; i < n - m; i++) {
            start.next = then.next;
            then.next = pre.next;
            pre.next = then;
            then = start.next;
        }
        return dummy.next;
    }
}