Boost Java Development with Hutool: 17 Essential Utility Classes Explained

Hutool is a small yet comprehensive Java utility library that helps simplify code and avoid reinventing the wheel; this article summarizes 17 commonly used utility classes.

Installation

Hutool can be added to a Maven project by including the following dependency in

pom.xml

:

<code>&lt;dependency&gt;
    &lt;groupId&gt;cn.hutool&lt;/groupId&gt;
    &lt;artifactId&gt;hutool-all&lt;/artifactId&gt;
    &lt;version&gt;${hutool.version}&lt;/version&gt;
&lt;/dependency&gt;
</code>

Common Utility Classes

Using a utility method instead of a block of complex code and avoiding copy‑paste can greatly improve development efficiency; below are the most frequently used methods.

Convert

The conversion utility class handles various type conversions, eliminating the need for repetitive try‑catch blocks.

<code>// Convert to string
int a = 1;
String aStr = Convert.toStr(a);
// Convert to int array
String[] b = {"1", "2", "3", "4"};
Integer[] bArr = Convert.toIntArray(b);
// Convert to date
String dateStr = "2017-05-06";
Date date = Convert.toDate(dateStr);
// Convert to list
String[] strArr = {"a", "b", "c", "d"};
List<String> strList = Convert.toList(String.class, strArr);
</code>

DateUtil

Date and time utility class provides convenient methods for common date operations, simplifying the cumbersome JDK Date and Calendar APIs.

<code>// Current date
Date date = DateUtil.date();
// Calendar to Date
date = DateUtil.date(Calendar.getInstance());
// Timestamp to Date
date = DateUtil.date(System.currentTimeMillis());
// Parse string to date
String dateStr = "2017-03-01";
date = DateUtil.parse(dateStr);
// Custom format parsing
date = DateUtil.parse(dateStr, "yyyy-MM-dd");
// Format date to string
String format = DateUtil.format(date, "yyyy-MM-dd");
// Get year and month
int year = DateUtil.year(date);
int month = DateUtil.month(date);
// Begin and end of day
Date beginOfDay = DateUtil.beginOfDay(date);
Date endOfDay = DateUtil.endOfDay(date);
// Offset date
Date newDate = DateUtil.offset(date, DateField.DAY_OF_MONTH, 2);
// Calculate difference in days
long betweenDay = DateUtil.between(date, newDate, DateUnit.DAY);
</code>

JSONUtil

JSON parsing utility class enables conversion between objects and JSON strings.

<code>PmsBrand brand = new PmsBrand();
brand.setId(1L);
brand.setName("Xiaomi");
brand.setShowStatus(1);
// Object to JSON string
String jsonStr = JSONUtil.parse(brand).toString();
LOGGER.info("jsonUtil parse:{}", jsonStr);
// JSON string to object
PmsBrand brandBean = JSONUtil.toBean(jsonStr, PmsBrand.class);
LOGGER.info("jsonUtil toBean:{}", brandBean);
// List conversion
List<PmsBrand> brandList = new ArrayList<>();
brandList.add(brand);
String jsonListStr = JSONUtil.parse(brandList).toString();
brandList = JSONUtil.toList(new JSONArray(jsonListStr), PmsBrand.class);
LOGGER.info("jsonUtil toList:{}", brandList);
</code>

StrUtil

String utility class offers concise methods for common string operations.

<code>// Check empty
String str = "test";
StrUtil.isEmpty(str);
StrUtil.isNotEmpty(str);
// Remove suffix/prefix
StrUtil.removeSuffix("a.jpg", ".jpg");
StrUtil.removePrefix("a.jpg", "a.");
// Format string
String template = "This is a placeholder:{}";
String str2 = StrUtil.format(template, "I am the placeholder");
LOGGER.info("/strUtil format:{}", str2);
</code>

ClassPathResource

Accesses resources on the classpath, useful for loading configuration files.

<code>// Load generator.properties from src/main/resources
ClassPathResource resource = new ClassPathResource("generator.properties");
Properties properties = new Properties();
properties.load(resource.getStream());
LOGGER.info("/classPath:{}", properties);
</code>

ReflectUtil

Reflection utility class simplifies method retrieval, object instantiation, and method invocation.

<code>// Get all methods of a class
Method[] methods = ReflectUtil.getMethods(PmsBrand.class);
// Get specific method
Method method = ReflectUtil.getMethod(PmsBrand.class, "getId");
// Create instance via reflection
PmsBrand pmsBrand = ReflectUtil.newInstance(PmsBrand.class);
// Invoke method
ReflectUtil.invoke(pmsBrand, "setId", 1);
</code>

NumberUtil

Number utility class provides arithmetic operations and type checks for various numeric types.

<code>double n1 = 1.234;
double n2 = 1.234;
double result;
result = NumberUtil.add(n1, n2);
result = NumberUtil.sub(n1, n2);
result = NumberUtil.mul(n1, n2);
result = NumberUtil.div(n1, n2);
BigDecimal roundNum = NumberUtil.round(n1, 2);
String n3 = "1.234";
NumberUtil.isNumber(n3);
NumberUtil.isInteger(n3);
NumberUtil.isDouble(n3);
</code>

BeanUtil

JavaBean utility class enables conversion between maps and beans and property copying.

<code>PmsBrand brand = new PmsBrand();
brand.setId(1L);
brand.setName("Xiaomi");
brand.setShowStatus(0);
// Bean to Map
Map<String, Object> map = BeanUtil.beanToMap(brand);
LOGGER.info("beanUtil bean to map:{}", map);
// Map to Bean
PmsBrand mapBrand = BeanUtil.toBean(map, PmsBrand.class);
LOGGER.info("beanUtil map to bean:{}", mapBrand);
// Copy properties
PmsBrand copyBrand = new PmsBrand();
BeanUtil.copyProperties(brand, copyBrand);
LOGGER.info("beanUtil copy properties:{}", copyBrand);
</code>

CollUtil

Collection utility class offers convenient methods for handling arrays, lists, sets, and other collections.

<code>// Array to List
String[] array = new String[]{"a", "b", "c", "d", "e"};
List<String> list = CollUtil.newArrayList(array);
// Join list to string
String joinStr = CollUtil.join(list, ",");
LOGGER.info("collUtil join:{}", joinStr);
// Split string back to list
List<String> splitList = StrUtil.split(joinStr, ',');
LOGGER.info("collUtil split:{}", splitList);
// Create new Set and List
HashSet<Object> newHashSet = CollUtil.newHashSet();
ArrayList<Object> newList = CollUtil.newArrayList();
// Check if list is empty
CollUtil.isEmpty(list);
</code>

MapUtil

Map utility class simplifies map creation and emptiness checks.

<code>// Create map with multiple entries
Map<Object, Object> map = MapUtil.of(new String[][]{
    {"key1", "value1"},
    {"key2", "value2"},
    {"key3", "value3"}
});
// Check map emptiness
MapUtil.isEmpty(map);
MapUtil.isNotEmpty(map);
</code>

AnnotationUtil

Annotation utility class retrieves annotations and their values from classes, methods, fields, etc.

<code>// Get all annotations on a class
Annotation[] annotationList = AnnotationUtil.getAnnotations(HutoolController.class, false);
LOGGER.info("annotationUtil annotations:{}", annotationList);
// Get specific annotation
Api api = AnnotationUtil.getAnnotation(HutoolController.class, Api.class);
LOGGER.info("annotationUtil api value:{}", api.description());
// Get annotation value
Object annotationValue = AnnotationUtil.getAnnotationValue(HutoolController.class, RequestMapping.class);
</code>

SecureUtil

Encryption utility class provides MD5 hashing.

<code>String str = "123456";
String md5Str = SecureUtil.md5(str);
LOGGER.info("secureUtil md5:{}", md5Str);
</code>

BCrypt

BCrypt utility class offers BCrypt hashing and verification, used by Spring Security.

<code>String str = "123456";
String bCryptStr = BCrypt.hashpw(str);
LOGGER.info("bCrypt hashpw:{}", bCryptStr);
boolean result = BCrypt.checkpw(str, bCryptStr);
LOGGER.info("bCrypt checkpw:{}", result);
</code>

CaptchaUtil

Captcha utility class generates image captchas.

<code>LineCaptcha lineCaptcha = CaptchaUtil.createLineCaptcha(200, 100);
try {
    request.getSession().setAttribute("CAPTCHA_KEY", lineCaptcha.getCode());
    response.setContentType("image/png");
    response.setHeader("Pragma", "No-cache");
    response.setHeader("Cache-Control", "no-cache");
    response.setDateHeader("Expire", 0);
    lineCaptcha.write(response.getOutputStream());
} catch (IOException e) {
    e.printStackTrace();
}
</code>

Validator

Validator utility class checks formats such as email, mobile, IP, Chinese characters, ID numbers, URLs, and birthdays.

<code>boolean result = Validator.isEmail("[email protected]");
LOGGER.info("Validator isEmail:{}", result);
result = Validator.isMobile("18911111111");
LOGGER.info("Validator isMobile:{}", result);
result = Validator.isIpv4("192.168.3.101");
LOGGER.info("Validator isIpv4:{}", result);
result = Validator.isChinese("你好");
LOGGER.info("Validator isChinese:{}", result);
result = Validator.isCitizenId("123456");
LOGGER.info("Validator isCitizenId:{}", result);
result = Validator.isUrl("http://www.baidu.com");
LOGGER.info("Validator isUrl:{}", result);
result = Validator.isBirthday("2020-02-01");
LOGGER.info("Validator isBirthday:{}", result);
</code>

DigestUtil

Digest utility class supports MD5, SHA‑256, and Bcrypt algorithms.

<code>String password = "123456";
String result = DigestUtil.md5Hex(password);
LOGGER.info("DigestUtil md5Hex:{}", result);
result = DigestUtil.sha256Hex(password);
LOGGER.info("DigestUtil sha256Hex:{}", result);
String hashPwd = DigestUtil.bcrypt(password);
boolean check = DigestUtil.bcryptCheck(password, hashPwd);
LOGGER.info("DigestUtil bcryptCheck:{}", check);
</code>

HttpUtil

HTTP request utility class can send GET/POST requests.

<code>String response = HttpUtil.get("http://localhost:8080/hutool/covert");
LOGGER.info("HttpUtil get:{}", response);
</code>

Other Utility Classes

Hutool provides many more utility classes; refer to the official site for the full list.

https://www.hutool.cn/

Project Source Code

Source code for this tutorial is available at:

https://github.com/macrozheng/mall-learning/tree/master/mall-tiny-hutool