Java连接mqtt服务器（发送、订阅）         <dependency>             <groupId>org.eclipse.paho</groupId>             <artifactId>org.eclipse.paho.client.mqttv3</artifactId>             <version>1.2.2</version>         </dependency>1.模拟客户端接收消息import java.util.concurrent.ScheduledExecutorService; import org.eclipse.paho.client.mqttv3.MqttClient; import org.eclipse.paho.client.mqttv3.MqttConnectOptions; import org.eclipse.paho.client.mqttv3.MqttTopic; import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence; /**  * 模拟一个客户端接收消息  *  * @author Unclue_liu  */ public class ClientMQTT {     public static final String HOST = "tcp://192.168.1.77:1883";     public static final String TOPIC1 = "pos_message_all";     private static final String clientid = "12345678";     private MqttClient client;     private MqttConnectOptions options;     private String userName = "mqtt";    //非必须     private String passWord = "mqtt";  //非必须     private ScheduledExecutorService scheduler;     private void start() {         try {             // host为主机名，clientid即连接MQTT的客户端ID，一般以唯一标识符表示，MemoryPersistence设置clientid的保存形式，默认为以内存保存             client = new MqttClient(HOST, clientid, new MemoryPersistence());             // MQTT的连接设置             options = new MqttConnectOptions();             // 设置是否清空session,这里如果设置为false表示服务器会保留客户端的连接记录，设置为true表示每次连接到服务器都以新的身份连接             options.setCleanSession(false);             // 设置连接的用户名             options.setUserName(userName);             // 设置连接的密码             options.setPassword(passWord.toCharArray());             // 设置超时时间 单位为秒             options.setConnectionTimeout(10);             // 设置会话心跳时间 单位为秒 服务器会每隔1.5*20秒的时间向客户端发送个消息判断客户端是否在线，但这个方法并没有重连的机制             options.setKeepAliveInterval(20);             //设置断开后重新连接             options.setAutomaticReconnect(true);             // 设置回调             client.setCallback(new PushCallback());             MqttTopic topic = client.getTopic(TOPIC1);             //setWill方法，如果项目中需要知道客户端是否掉线可以调用该方法。设置最终端口的通知消息             //遗嘱             options.setWill(topic, "close".getBytes(), 1, true);             client.connect(options);             //订阅消息             int[] Qos = {1};//0：最多一次 、1：最少一次 、2：只有一次             String[] topic1 = {TOPIC1};             client.subscribe(topic1, Qos);         } catch (Exception e) {             e.printStackTrace();         }     }     public static void main(String[] args)  {         ClientMQTT client = new ClientMQTT();         client.start();     }2.模拟服务端发送消息import org.eclipse.paho.client.mqttv3.MqttClient; import org.eclipse.paho.client.mqttv3.MqttConnectOptions; import org.eclipse.paho.client.mqttv3.MqttDeliveryToken; import org.eclipse.paho.client.mqttv3.MqttException; import org.eclipse.paho.client.mqttv3.MqttMessage; import org.eclipse.paho.client.mqttv3.MqttPersistenceException; import org.eclipse.paho.client.mqttv3.MqttTopic; import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence; /**  * Title:Server 这是发送消息的服务端  * Description: 服务器向多个客户端推送主题，即不同客户端可向服务器订阅相同主题  * @author Unclue_liu  */ public class ServerMQTT {     //tcp://MQTT安装的服务器地址:MQTT定义的端口号     public static final String HOST = "tcp://192.168.1.77:1883";     //定义一个主题     public static final String TOPIC = "pos_message_all";     //定义MQTT的ID，可以在MQTT服务配置中指定     private static final String clientid = "server11";     private MqttClient client;     private static MqttTopic topic11; //    private String userName = "mqtt";  //非必须 //    private String passWord = "mqtt";  //非必须     private static MqttMessage message;     /**      * 构造函数      * @throws MqttException      */     public ServerMQTT() throws MqttException {         // MemoryPersistence设置clientid的保存形式，默认为以内存保存         client = new MqttClient(HOST, clientid, new MemoryPersistence());         connect();     }     /**      *  用来连接服务器      */     private void connect() {         MqttConnectOptions options = new MqttConnectOptions();         options.setCleanSession(false); //        options.setUserName(userName); //        options.setPassword(passWord.toCharArray());         // 设置超时时间         options.setConnectionTimeout(10);         // 设置会话心跳时间         options.setKeepAliveInterval(20);         try {             client.setCallback(new PushCallback());             client.connect(options);             topic11 = client.getTopic(TOPIC);         } catch (Exception e) {             e.printStackTrace();         }     }     /**      *      * @param topic      * @param message      * @throws MqttPersistenceException      * @throws MqttException      */     public static void publish(MqttTopic topic , MqttMessage message) throws MqttPersistenceException,             MqttException {         MqttDeliveryToken token = topic.publish(message);         token.waitForCompletion();         System.out.println("message is published completely! "                 + token.isComplete());     }     public static void sendMessage(String clieId,String msg)throws Exception{         ServerMQTT server = new ServerMQTT();         server.message = new MqttMessage();         server.message.setQos(1);  //保证消息能到达一次         server.message.setRetained(true);         String str ="{\"clieId\":\""+clieId+"\",\"mag\":\""+msg+"\"}";         server.message.setPayload(str.getBytes());         try{             publish(server.topic11 , server.message);             //断开连接 //            server.client.disconnect();         }catch (Exception e){             e.printStackTrace();         }     }     /**      *  启动入口      * @param args      * @throws MqttException      */     public static void main(String[] args) throws Exception {         sendMessage("123444","哈哈");     } }3.发布消息回调类import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken; import org.eclipse.paho.client.mqttv3.MqttCallback; import org.eclipse.paho.client.mqttv3.MqttMessage; /**  * 发布消息的回调类  *  * 必须实现MqttCallback的接口并实现对应的相关接口方法CallBack 类将实现 MqttCallBack。  * 每个客户机标识都需要一个回调实例。在此示例中，构造函数传递客户机标识以另存为实例数据。  * 在回调中，将它用来标识已经启动了该回调的哪个实例。  * 必须在回调类中实现三个方法：  *  *  public void messageArrived(MqttTopic topic, MqttMessage message)接收已经预订的发布。  *  *  public void connectionLost(Throwable cause)在断开连接时调用。  *  *  public void deliveryComplete(MqttDeliveryToken token))  *  接收到已经发布的 QoS 1 或 QoS 2 消息的传递令牌时调用。  *  由 MqttClient.connect 激活此回调。  *  */ public class PushCallback implements MqttCallback {     public void connectionLost(Throwable cause) {         // 连接丢失后，一般在这里面进行重连         System.out.println("连接断开，可以做重连");     }     public void deliveryComplete(IMqttDeliveryToken token) {         System.out.println("deliveryComplete---------" + token.isComplete());     }     public void messageArrived(String topic, MqttMessage message) throws Exception {         // subscribe后得到的消息会执行到这里面         System.out.println("接收消息主题 : " + topic);         System.out.println("接收消息Qos : " + message.getQos());         System.out.println("接收消息内容 : " + new String(message.getPayload()));     } } 

java 根据html模板生成html文件 1.代码部分import org.junit.Test; import org.junit.runner.RunWith; import org.springframework.boot.test.context.SpringBootTest; import org.springframework.test.context.junit4.SpringRunner; import java.io.FileInputStream; import java.io.FileOutputStream; @RunWith(SpringRunner.class) @SpringBootTest public class PdfApplicationTests { @Test public void contextLoads() { String filePath = "D:\\WorkSpace\\IdeaProjects\\pdf\\src\\main\\resources\\templates\\index.html"; String text ="哈哈"; String disrPath = "D:\\WorkSpace\\IdeaProjects\\pdf\\src\\main\\resources\\templates"; String fileName = "t"; MakeHtml(filePath,text,disrPath,fileName); } /** * @Title: MakeHtml * @Description: 创建html * @param filePath 设定模板文件 * @param text 添加的内容 * @param disrPath 生成html的存放路径 * @param fileName 生成html名字 * @return void 返回类型 * @throws */ public static void MakeHtml(String filePath,String text,String disrPath,String fileName ){ try { String title = "<h2>"+text+"</h2>"; System.out.print(filePath); String templateContent = ""; FileInputStream fileinputstream = new FileInputStream(filePath);// 读取模板文件 int lenght = fileinputstream.available(); byte bytes[] = new byte[lenght]; fileinputstream.read(bytes); fileinputstream.close(); templateContent = new String(bytes); System.out.print(templateContent); //把模板页面上的 ###text### 替换成 title 里的内容 templateContent = templateContent.replaceAll("###text###", title); System.out.print(templateContent); String fileame = fileName + ".html"; fileame = disrPath+"/" + fileame;// 生成的html文件保存路径。 FileOutputStream fileoutputstream = new FileOutputStream(fileame);// 建立文件输出流 System.out.print("文件输出路径:"); System.out.print(fileame); byte tag_bytes[] = templateContent.getBytes(); fileoutputstream.write(tag_bytes); fileoutputstream.close(); } catch (Exception e) { System.out.print(e.toString()); } } } 2.模板页<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"/> <title>Title</title> </head> </head> <body> ###text### </body> </html>3.生成的html<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"/> <title>Title</title> </head> </head> <body> <h2>哈哈</h2> </body> </html> 

java根据xml模板生成word（编辑内容） 1.使用的依赖 <dependency> <groupId>org.freemarker</groupId> <artifactId>freemarker</artifactId> <version>2.3.25-incubating</version> </dependency>2.Servicepackage com.hj.test; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.OutputStreamWriter; import java.io.Writer; import java.net.URL; import java.util.*; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service; import freemarker.cache.URLTemplateLoader; import freemarker.core.ParseException; import freemarker.template.Configuration; import freemarker.template.MalformedTemplateNameException; import freemarker.template.Template; import freemarker.template.TemplateException; import freemarker.template.TemplateNotFoundException; import javax.servlet.http.HttpServletRequest; @Service public class DynamicallyGeneratedWordService { private static Configuration freemarkerConfig; @Autowired HttpServletRequest req; static { freemarkerConfig = new Configuration(Configuration.VERSION_2_3_22); freemarkerConfig.setEncoding(Locale.getDefault(), "UTF-8"); } /** * 生成word文档 * @param filePath * @throws TemplateNotFoundException * @throws MalformedTemplateNameException * @throws ParseException * @throws IOException * @throws TemplateException */ public void genWordFile(String filePath) throws TemplateNotFoundException, MalformedTemplateNameException, ParseException, IOException, TemplateException{ Map<String,Object> result = new HashMap<String,Object>(); result.put("topic", "基于Java模板技术动态生成Word文档"); freemarkerConfig.setTemplateLoader(new URLTemplateLoader() { @Override protected URL getURL(String arg0) { //此处访问的地址是项目target/classes文件夹 //输出的类似：E:/software/idea/aa/target/classes/6.xm return DynamicallyGeneratedWordService.class.getResource("/6.xml"); } }); Template temp = freemarkerConfig.getTemplate("6.xml"); File targetFile = new File(filePath); Writer out = new OutputStreamWriter(new FileOutputStream(targetFile),"UTF-8"); //执行模板替换 temp.process(result, out); out.flush(); } }  xml地址：3.Controllerpackage com.hj.test; import java.io.IOException; import java.util.List; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.ResponseBody; import com.hj.test.Student; import com.hj.test.DynamicallyGeneratedWordService; import freemarker.core.ParseException; import freemarker.template.MalformedTemplateNameException; import freemarker.template.TemplateException; import freemarker.template.TemplateNotFoundException; /** * @author Solin * 基于Java模板技术动态生成Word文档 */ @Controller public class DynamicallyGeneratedWordController { @Autowired private DynamicallyGeneratedWordService dynamicallyGeneratedWordService; @ResponseBody @RequestMapping("/getStudentList") public String getStudentList(){ String result = "成功"; try { dynamicallyGeneratedWordService.genWordFile("d://stu.doc"); } catch (TemplateNotFoundException e) { result = "失败"; e.printStackTrace(); } catch (MalformedTemplateNameException e) { result = "失败"; e.printStackTrace(); } catch (ParseException e) { result = "失败"; e.printStackTrace(); } catch (IOException e) { result = "失败"; e.printStackTrace(); } catch (TemplateException e) { result = "失败"; e.printStackTrace(); } return result; } } 编辑xml文件：（xml模板可编辑word文档使用wps另存为xml格式） 参考：https://blog.csdn.net/qq_32786873/article/details/52535845

Java跨域 mport org.springframework.stereotype.Component; import javax.servlet.*; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; /** * 跨域 */ @Component public class CorsFilter implements Filter { @Override public void init(FilterConfig filterConfig) throws ServletException { } @Override public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { HttpServletRequest request = (HttpServletRequest) servletRequest; HttpServletResponse response = (HttpServletResponse) servletResponse; response.setHeader("Access-Control-Allow-Origin", request.getHeader("origin")); // response.setHeader("Access-Control-Allow-Origin", "*");//允许跨域访问的域 response.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE");//允许使用的请求方法，以逗号隔开 response.setHeader("Access-Control-Max-Age", "3600");// 缓存此次请求的秒数 //允许使用的请求方法，以逗号隔开 response.setHeader("Access-Control-Allow-Headers", "x-requested-with,Cache-Control,Pragma,Content-Type,Token"); response.setHeader("Access-Control-Allow-Credentials","true");//是否允许请求带有验证信息 filterChain.doFilter(servletRequest, servletResponse); } @Override public void destroy() { } } 

Java获取前一天的的日期         //Date d=new Date(System.currentTimeMillis()-1000*60*60*24*2);//计算前天         Date d=new Date(System.currentTimeMillis()-1000*60*60*24);         SimpleDateFormat sp=new SimpleDateFormat("yyyy-MM-dd");         String zuotian=sp.format(d);//获取昨天日期 

java.lang.NoClassDefFoundError: com/sun/image/codec/jpeg/JPEGCodec 图片压缩在windows下正常，linux服务器报java.lang.NoClassDefFoundError: com/sun/image/codec/jpeg/JPEGCodec本地开发，jre里有这个包，所以不会报错但是在新的 jdk 版本中，这个类不推荐使用了，使用 ImageIO.write 方法替代// JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(fos); // encoder.encode(image); ImageIO.write(image, "jpg", fos); 

java调用接口，同时上传文件及数据  1.提交数据/** * POST报文客户端 * * @param url 调用地址字符串 * @param jsonParam 报文实体JSON * @return String * @author Al1en */ public static String httpPostWithForm(String url, JSONObject jsonParam) { URL u = null; HttpURLConnection con = null; // 构建请求参数 StringBuffer sb = new StringBuffer(); for (String s : jsonParam.keySet()) { sb.append(s); sb.append("="); sb.append(jsonParam.getString(s)); sb.append("&"); } System.out.println("send_url:" + url); System.out.println("send_data:" + sb.toString()); // 尝试发送请求 try { u = new URL(url); con = (HttpURLConnection) u.openConnection(); POST 只能为大写，严格限制，post会不识别 con.setRequestMethod("POST"); con.setDoOutput(true); con.setDoInput(true); con.setUseCaches(false); con.setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); OutputStreamWriter osw = new OutputStreamWriter(con.getOutputStream(), "UTF-8"); osw.write(sb.toString()); osw.flush(); osw.close(); } catch (Exception e) { e.printStackTrace(); } finally { if (con != null) { con.disconnect(); } } // 读取返回内容 StringBuffer buffer = new StringBuffer(); try { //一定要有返回值，否则无法把请求发送给server端。 BufferedReader br = new BufferedReader(new InputStreamReader(con.getInputStream(), "UTF-8")); String temp; while ((temp = br.readLine()) != null) { buffer.append(temp); buffer.append("\n"); } } catch (Exception e) { e.printStackTrace(); } return buffer.toString(); } 2.提交数据及文件 import java.io.*; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.ProtocolException; import java.net.URL; import java.util.HashMap; import java.util.Map; public class HttpPost { private static final String BOUNDARY = "-------45962402127348"; private static final String FILE_ENCTYPE = "multipart/form-data"; //存放数据 Map<String, String> textParams = new HashMap<String, String>(); //存放File文件 Map<String, File> fileparams = new HashMap<String, File>(); String url; public HttpPost(String url)throws Exception{ this.url = url; } public void setUrl(String url) { this.url = url; } public void addTextParams(String key,String value) { this.textParams.put(key, value); } public void addFileparams(String key,File file) { this.fileparams.put(key, file); } public String send()throws IOException{ InputStream post = post(this.url, this.textParams, this.fileparams); ByteArrayOutputStream out = new ByteArrayOutputStream(); int b; while ((b = post.read()) != -1) { out.write(b); } return new String(out.toByteArray()); } /** * * @param urlStr http请求路径 * @param params 请求参数 * @param images 上传文件 * @return */ public static InputStream post(String urlStr, Map<String, String> params, Map<String, File> images) { InputStream is = null; try { URL url = new URL(urlStr); HttpURLConnection con = (HttpURLConnection) url.openConnection(); con.setConnectTimeout(5000); con.setDoInput(true); con.setDoOutput(true); con.setUseCaches(false); con.setRequestMethod("POST"); con.setRequestProperty("Connection", "Keep-Alive"); con.setRequestProperty("Charset", "UTF-8"); con.setRequestProperty("Content-Type", FILE_ENCTYPE + "; boundary=" + BOUNDARY); StringBuilder sb = null; DataOutputStream dos = new DataOutputStream(con.getOutputStream());; if (params != null) { sb = new StringBuilder(); for (String s : params.keySet()) { sb.append("--"); sb.append(BOUNDARY); sb.append("\r\n"); sb.append("Content-Disposition: form-data; name=\""); sb.append(s); sb.append("\"\r\n\r\n"); sb.append(params.get(s)); sb.append("\r\n"); } dos.write(sb.toString().getBytes()); } if (images != null) { for (String s : images.keySet()) { File f = images.get(s); sb = new StringBuilder(); sb.append("--"); sb.append(BOUNDARY); sb.append("\r\n"); sb.append("Content-Disposition: form-data; name=\""); sb.append(s); sb.append("\"; filename=\""); sb.append(f.getName()); sb.append("\"\r\n"); sb.append("Content-Type: multipart/form-data");//这里注意！如果上传的不是图片，要在这里改文件格式，比如txt文件，这里应该是text/plain sb.append("\r\n\r\n"); dos.write(sb.toString().getBytes()); FileInputStream fis = new FileInputStream(f); byte[] buffer = new byte[1024]; int len; while ((len = fis.read(buffer)) != -1) { dos.write(buffer, 0, len); } dos.write("\r\n".getBytes()); fis.close(); } sb = new StringBuilder(); sb.append("--"); sb.append(BOUNDARY); sb.append("--\r\n"); dos.write(sb.toString().getBytes()); } dos.flush(); if (con.getResponseCode() == 200){ is = con.getInputStream(); } dos.close(); } catch (MalformedURLException e) { e.printStackTrace(); } catch (ProtocolException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } return is; } public static void main(String[] args)throws Exception { HttpPost post = new HttpPost("http://***"); post.addTextParams("a", "1"); post.addTextParams("b", "hahah"); post.addTextParams("c", "你好"); post.addFileparams("verifyFace", new File("c:/123.jpg")); String result = post.send(); System.out.println(result); } }  

Java SpringBoot 循环监听UDP同一个Socket实现接收与发送 SpringBoot实现项目启动监听UDP package com.hujiang.project.lz.faceRecognition; import javax.servlet.ServletContextEvent; import javax.servlet.ServletContextListener; import javax.servlet.annotation.WebListener; import java.io.*; import java.net.*; import java.util.logging.Logger; /* * 服务器端，实现基于UDP的用户登陆 */ @WebListener public class UDPServer implements ServletContextListener { public static Logger logger = Logger.getLogger(UDPServer.class.getName()); public static final int MAX_UDP_DATA_SIZE = 4096; public static final int UDP_PORT = 6007; public static DatagramPacket packet = null; public static DatagramSocket socket = null; @Override public void contextInitialized(ServletContextEvent sce) { try { logger.info("========启动一个线程，监听UDP数据报.PORT:" + UDP_PORT + "========="); // 启动一个线程，监听UDP数据报 new Thread(new UDPProcess(UDP_PORT)).start(); } catch (Exception e) { e.printStackTrace(); } } class UDPProcess implements Runnable { public UDPProcess(final int port) throws SocketException { //创建服务器端DatagramSocket，指定端口 socket = new DatagramSocket(port); } @Override public void run() { // TODO Auto-generated method stub logger.info("=======创建数据报，用于接收客户端发送的数据======"); while (true) { byte[] buffer = new byte[MAX_UDP_DATA_SIZE]; packet = new DatagramPacket(buffer, buffer.length); try { logger.info("=======此方法在接收到数据报之前会一直阻塞======"); socket.receive(packet); new Thread(new Process(packet)).start(); } catch (IOException e) { e.printStackTrace(); } } } } class Process implements Runnable { public Process(DatagramPacket packet) throws UnsupportedEncodingException { // TODO Auto-generated constructor stub logger.info("=======接收到的UDP信息======"); byte[] buffer = packet.getData();// 接收到的UDP信息，然后解码 // String srt1 = new String(buffer, "GBK").trim(); // logger.info("=======Process srt1 GBK======" + srt1); String srt2 = new String(buffer, "UTF-8").trim(); logger.info("=======Process srt2 UTF-8======" + srt2); // String srt3 = new String(buffer, "ISO-8859-1").trim(); // logger.info("=======Process srt3 ISO-8859-1======" + srt3); } @Override public void run() { // TODO Auto-generated method stub logger.info("====过程运行====="); try { logger.info("====向客户端响应数据====="); //1.定义客户端的地址、端口号、数据 InetAddress address = packet.getAddress(); int port = packet.getPort(); byte[] data2 = "{'request':'alive','errcode':'0'}".getBytes(); //2.创建数据报，包含响应的数据信息 DatagramPacket packet2 = new DatagramPacket(data2, data2.length, address, port); //3.响应客户端 socket.send(packet2); } catch (Exception e) { e.printStackTrace(); } } } @Override public void contextDestroyed(ServletContextEvent sce) { logger.info("========UDPListener摧毁========="); } }  @ServletComponentScan Servlet扫描，启动时把servlet、filter、listener自动扫描注入@SpringBootApplication @ServletComponentScan public class DemoApplication { public static void main(String[] args) { SpringApplication.run(DemoApplication.class, args); } } 创建客户端测试 public static final String SERVER_HOSTNAME = "localhost"; // 服务器端口 public static final int SERVER_PORT = 6007; // 本地发送端口 public static final int LOCAL_PORT = 8888; public static void main(String[] args) { try { // 1，创建udp服务。通过DatagramSocket对象。 DatagramSocket socket = new DatagramSocket(LOCAL_PORT); // 2，确定数据，并封装成数据包。DatagramPacket(byte[] buf, int length, InetAddress // address, int port) byte[] buf = "你好，世界".getBytes(); DatagramPacket dp = new DatagramPacket(buf, buf.length, InetAddress.getByName(SERVER_HOSTNAME), SERVER_PORT); // 3，通过socket服务，将已有的数据包发送出去。通过send方法。 socket.send(dp); // 4，关闭资源。 socket.close(); } catch (IOException e) { e.printStackTrace(); } }  

java.lang.IllegalStateException: Failed to load property source from location 'classpath:/applicatio 异常问题：java.lang.IllegalStateException: Failed to load property source from location 'classpath:/application.yml' 可能是application.yml文件内容格式或层级的问题

Java8 日期时间 @Test public void test(){ testLocalDateTime(); } public void testLocalDateTime(){ // 获取当前的日期时间 LocalDateTime currentTime = LocalDateTime.now(); System.out.println("当前时间: " + currentTime);//当前时间: 2019-11-01T15:21:42.281 LocalDate date1 = currentTime.toLocalDate(); System.out.println("date1: " + date1);//date1: 2019-11-01 Month month = currentTime.getMonth(); int day = currentTime.getDayOfMonth(); int seconds = currentTime.getSecond(); System.out.println("月: " + month +", 日: " + day +", 秒: " + seconds);//月: NOVEMBER, 日: 1, 秒: 42 LocalDateTime date2 = currentTime.withDayOfMonth(10).withYear(2012); System.out.println("date2: " + date2);//2012-11-10T15:21:42.281 // 12 december 2014 LocalDate date3 = LocalDate.of(2014, Month.DECEMBER, 12); System.out.println("date3: " + date3);//2014-12-12 // 22 小时 15 分钟 LocalTime date4 = LocalTime.of(22, 15); System.out.println("date4: " + date4);//22:15 // 解析字符串 LocalTime date5 = LocalTime.parse("20:15:30"); System.out.println("date5: " + date5);//20:15:30 }