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response.setHeader("Access-Control-Allow-Origin", "*");
// or
response.setHeader("Access-Control-Allow-Origin", "http://localhost");

response.setHeader("Access-Control-Allow-Methods", "DELETE");

response.setHeader("Access-Control-Allow-Headers", "my-header1");

response.setHeader("Access-Control-Allow-Credentials", "true");

response.setHeader("Access-Control-Allow-Origin", "*"); // You can also set a specific host.
response.setHeader("Access-Control-Allow-Methods", "POST, GET, PATCH, DELETE, PUT, PATCH");
response.setHeader("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept, {my-custome-header}");
response.setHeader("Access-Control-Max-Age", "86400");

response.setHeader("Access-Control-Allow-Origin", "{your_host}"); // If you use a web framework, it may support setting allow-origin patterns. For example, http://localhost:[*], http://192.168.0.*:[*].
response.setHeader("Access-Control-Allow-Credentials", "true");
response.setHeader("Access-Control-Allow-Methods", "POST, GET, PATCH, DELETE, PUT, PATCH");
response.setHeader("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept, {my-custome-header}");
response.setHeader("Access-Control-Max-Age", "86400");

public class LogicProcessingUtils {
    /**
     * @param maxTryTimes
     * @param successPredicate
     * @param function
     * @param params           parameter object
     * @param <T>              function return type
     * @param <P>              function parameter type
     * @return
     */
    public static <T, P> T tryToGetResult(int maxTryTimes,
                                          Predicate<T> successPredicate,
                                          Function<P, T> function,
                                          P param) {
        int tryTimes = 0;
        T t = null;
        while (tryTimes < maxTryTimes) {
            t = function.apply(param);
            // System.out.println(t);
            if (successPredicate.test(t)) {
                break;
            }
            tryTimes++;
        }
        return t;
    }

    public static <T> T tryToGetResult(int maxTryTimes,
                                          Predicate<T> successPredicate,
                                          Supplier<T> supplier) {
        int tryTimes = 0;
        T t = null;
        while (tryTimes < maxTryTimes) {
            t = supplier.get();
            // System.out.println(t);
            if (successPredicate.test(t)) {
                break;
            }
            tryTimes++;
        }
        return t;
    }
}

public class MyTest {
    public static void main(String[] args) {
        MyTest myTest = new MyTest();
        int maxTryTimes = 3;
        ObjectNode result = LogicProcessingUtils.tryToGetResult(
                maxTryTimes,
                jsonNode -> jsonNode.get("code").asInt() == 200,
                myTest::getResult,
                0);
        System.out.println(result);
    }

    public ObjectNode getResult(Object param)  {
        System.out.println("param: " + param);
        ThreadLocalRandom random = ThreadLocalRandom.current();
        int randomNumber = random.nextInt(10);
        System.out.println("random number: " + randomNumber);
        String jsonStr = "{\"code\":500,\"data\":%d,\"msg\":\"请求失败\"}";
        ObjectMapper objectMapper = new ObjectMapper();
        try {
            return (ObjectNode) objectMapper.readTree(String.format(jsonStr, randomNumber));
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        return null;
    }
}

public static void executorService() {
    int threadNum = 10;
    ExecutorService executorService = Executors.newFixedThreadPool(threadNum);
    long start = System.currentTimeMillis();
    List<Future> futureList = new ArrayList<>(threadNum);
    for (int i = 0; i < threadNum; i++) {
        Future<String> future = executorService.submit(() -> {
            ThreadLocalRandom random = ThreadLocalRandom.current();
            int randomNumber = random.nextInt(10);
            System.out.println(Thread.currentThread().getName() + ": " + randomNumber);
            Thread.sleep(1000 * randomNumber);
            return Thread.currentThread().getName();
        });
        futureList.add(future);
    }
    for (int i = 0; i < threadNum; i++) {
        try {
            System.out.println(futureList.get(i).get());
            System.out.println("elapsed time: " + (System.currentTimeMillis() - start) + "ms");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    System.out.println("elapsed time: " + (System.currentTimeMillis() - start) + "ms");
    executorService.shutdown();
}

public static void executorCompletionService() {
    int threadNum = 10;
    ExecutorService executorService = Executors.newFixedThreadPool(threadNum);
    ExecutorCompletionService completionService =
            new ExecutorCompletionService<>(executorService);
    long start = System.currentTimeMillis();
    for (int i = 0; i < threadNum; i++) {
        completionService.submit(() -> {
            ThreadLocalRandom random = ThreadLocalRandom.current();
            int randomNumber = random.nextInt(10);
            System.out.println(Thread.currentThread().getName() + ": " + randomNumber);
            Thread.sleep(1000 * randomNumber);
            return Thread.currentThread().getName();
        });
    }
    for (int i = 0; i < threadNum; i++) {
        try {
            System.out.println(completionService.take().get());
            System.out.println("elapsed time: " + (System.currentTimeMillis() - start) + "ms");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    System.out.println("elapsed time: " + (System.currentTimeMillis() - start) + "ms");
    executorService.shutdown();
}

@GetMapping("testDateTime1")
public String testDateTime(@DateTimeFormat(pattern = "yyyy-MM-dd HH:mm:ss") Date dateTime) {
    ...
}

@RequestMapping("testDateTime2")
public String testDateTime2(QueryVo queryVo) {
	...
}
public class QueryVo {
    @DateTimeFormat(pattern = "yyyy-MM-dd HH:mm:ss")
    private Date dateTime;
}

@PostMapping("testDateTime3")
public String testDateTime3(@RequestBody QueryVo queryVo) {
    System.out.println("testDateTime");
    return queryVo.toString();
}

public class QueryVo {
    @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss", timezone = "GMT+8")
    private Date dateTime;
}

// Java 8
int size = 1, min = 0, max = 10;
ThreadLocalRandom random = ThreadLocalRandom.current();
int randomNumber = random.ints(size, min, max + 1).findFirst().getAsInt();

int size = 5, min = 0, max = 10;
ThreadLocalRandom random = ThreadLocalRandom.current();
int[] randomNumbers = random.ints(size, min, max + 1).toArray();

int size = 5, min = 0, max = 10;
Random random = new Random();
int[] randomNumbers = random.ints(size, min, max + 1).toArray();

// Java 1.7 or later
int min = 0, max = 10;
ThreadLocalRandom random = ThreadLocalRandom.current();
int randomNum = random.nextInt(min, max + 1);

// Before Java 1.7
int min = 0, max = 10;
Random random = new Random();
int randomNum = random.nextInt((max - min) + 1) + min;

int randomNum = min + (int) (Math.random() * ((max - min) + 1));

String source = "hello there, I am a Java developer. She is a Web developer.";
Pattern pattern = Pattern.compile("a (.*?) developer");
Matcher matcher = pattern.matcher(source);
System.out.println(matcher.matches()); // false

Pattern pattern2 = Pattern.compile(".*a (.*?) developer.*");
Matcher matcher2 = pattern2.matcher(source);
System.out.println(matcher2.matches()); // true

String source = "hello there, I am a Java developer. She is a Web developer.";
Pattern pattern = Pattern.compile("a (.*?) developer", Pattern.CASE_INSENSITIVE);
Matcher matcher = pattern.matcher(source);
// find all match strings
while (matcher.find()) {
    System.out.println(matcher.group()); // a Java developer, a Web developer
    for (int i = 1; i < matcher.groupCount(); i++) {
        System.out.println(matcher.group(i)); // Java, Web
    }
}
// reset matcher for reuse
matcher.reset();
// only find once
if (matcher.find()) {
    System.out.println(matcher.group()); // a Java developer
    System.out.println(matcher.group(1)); // Java
}

String source = "hello there, I am a Java developer. She is a Web developer.";
String regex = "a (.*?) developer";
int groupToReplace = 1;
String replacement = "Good";
Matcher matcher = Pattern.compile(regex).matcher(source);
StringBuilder result = new StringBuilder(source);
int adjust = 0;
while (matcher.find()) {
    int start = matcher.start(groupToReplace);
    int end = matcher.end(groupToReplace);
    result.replace(start + adjust, end + adjust, replacement);
    adjust += replacement.length() - (end - start);
}
System.out.println(result); //hello there, I am a Good developer. She is a Good developer.

// Pattern.DOTALL
Pattern.compile("regexStr", Pattern.DOTALL);

// Pattern.CASE_INSENSITIVE
Pattern.compile("regexStr", Pattern.CASE_INSENSITIVE)

// (?i) enables case-insensitivity
String regexStr = "(?i).*";
src.matches(regexStr);

// convert string cases
src.toLowerCase();
src.matches(regexStr);

Pattern.compile("regexStr", Pattern.DOTALL | Pattern.CASE_INSENSITIVE);

private static final String GOTENBERG_SERVICE_HOST = "http://xxx.xxx.xxx.xxx:3000";

private static final String CONVERT_TO_PDF_URI = "/forms/libreoffice/convert";

private static final OkHttpClient OKHTTP_CLIENT = new OkHttpClient.Builder()
    .connectTimeout(20, TimeUnit.SECONDS)
    .readTimeout(15, TimeUnit.SECONDS)
    .writeTimeout(15, TimeUnit.SECONDS)
    .build();

public static byte[] convertToPdfByGotenberg(InputStream inputStream, String fileName) throws IOException {
    Request.Builder requestBuilder = new Request.Builder()
        .url(HttpUrl.parse(GOTENBERG_SERVICE_HOST + CONVERT_TO_PDF_URI).newBuilder().build());
    String mediaType = URLConnection.guessContentTypeFromName(fileName);
    if (mediaType == null) {
        mediaType = "application/octet-stream";
    }
    MultipartBody.Builder builder = new MultipartBody.Builder()
        .setType(MultipartBody.FORM)
        .addFormDataPart("files", fileName,
                         RequestBody.create(MediaType.parse(mediaType),
                                            IOUtils.toByteArray(inputStream)));
    requestBuilder.post(builder.build());
    try (Response response = OKHTTP_CLIENT.newCall(requestBuilder.build()).execute()) {
        return response.body().bytes();
    }
}