Hutool

// Core utilities - most commonly used
import cn.hutool.core.util.*;

// Specific utilities
import cn.hutool.core.util.StrUtil;
import cn.hutool.core.util.DateUtil;
import cn.hutool.core.util.RandomUtil;
import cn.hutool.core.bean.BeanUtil;
import cn.hutool.core.collection.CollUtil;
import cn.hutool.core.convert.Convert;
import cn.hutool.core.io.FileUtil;
import cn.hutool.core.io.IoUtil;

// Specialized modules
import cn.hutool.http.HttpUtil;
import cn.hutool.json.JSONUtil;
import cn.hutool.crypto.SecureUtil;
import cn.hutool.db.DbUtil;
import cn.hutool.log.StaticLog;

import cn.hutool.core.util.*;
import cn.hutool.http.HttpUtil;
import cn.hutool.json.JSONUtil;

// String operations
String result = StrUtil.format("Hello {}, welcome to {}", "World", "Hutool");
boolean isEmpty = StrUtil.isBlank("   ");

// Date operations  
String dateStr = DateUtil.format(new Date(), "yyyy-MM-dd HH:mm:ss");
Date parsed = DateUtil.parse("2023-01-01", "yyyy-MM-dd");

// HTTP requests
String response = HttpUtil.get("https://api.example.com/data");
String jsonPost = HttpUtil.post("https://api.example.com/submit", "{\"key\":\"value\"}");

// JSON processing
JSONObject json = JSONUtil.createObj()
    .put("name", "hutool")
    .put("version", "5.8.40");
String jsonStr = json.toString();

// File operations
String content = FileUtil.readUtf8String("config.txt");
FileUtil.writeUtf8String("output.txt", "Hello Hutool");

// Random data generation
String randomStr = RandomUtil.randomString(10);
int randomInt = RandomUtil.randomInt(1, 100);

// Validation methods
public static boolean isBlank(CharSequence str);
public static boolean isEmpty(CharSequence str);
public static boolean isNotBlank(CharSequence str);

// Formatting and manipulation
public static String format(String template, Object... params);
public static String join(CharSequence delimiter, Object... elements);
public static String[] split(CharSequence str, CharSequence separator);

// Parsing and formatting
public static Date parse(CharSequence dateStr, String format);
public static String format(Date date, String format);

// Date calculations
public static Date offset(Date date, DateField dateField, int offset);
public static long between(Date beginDate, Date endDate, DateUnit unit);

// Simple HTTP methods
public static String get(String urlString);
public static String post(String urlString, String body);
public static HttpResponse execute(HttpRequest request);

// File operations
public static long downloadFile(String url, File targetFile);

// JSON creation and parsing
public static JSONObject createObj();
public static JSONArray createArray();
public static JSONObject parseObj(String jsonStr);
public static JSONArray parseArray(String jsonStr);

// Bean operations
public static void copyProperties(Object source, Object target);
public static <T> T toBean(Object source, Class<T> targetType);
public static Map<String, Object> beanToMap(Object bean);

// Collection operations
public static <T> List<T> newArrayList(T... values);
public static boolean isEmpty(Collection<?> collection);
public static <T> List<T> filter(Collection<T> collection, Predicate<T> predicate);

// File operations
public static String readUtf8String(File file);
public static void writeUtf8String(String content, File file);
public static void copy(File src, File dest);

// Stream operations
public static String read(InputStream in, Charset charset);
public static void copy(InputStream in, OutputStream out);

// Hash operations
public static String md5(String data);
public static String sha256(String data);

// Symmetric encryption
public static SymmetricCrypto aes(byte[] key);
public static SymmetricCrypto des(byte[] key);

// Database operations
public static List<Entity> findAll(String tableName);
public static Entity findById(String tableName, Object id);
public static int insert(String tableName, Entity entity);

// Validation
public static boolean isEmail(CharSequence email);
public static boolean isPhone(CharSequence mobile);

// Random generation
public static String randomString(int length);
public static int randomInt(int min, int max);

// Reflection
public static <T> T newInstance(Class<T> clazz, Object... params);
public static Object invoke(Object obj, String methodName, Object... args);

// Date field enumeration
public enum DateField {
    YEAR, MONTH, DAY_OF_MONTH, HOUR_OF_DAY, MINUTE, SECOND, MILLISECOND
}

// Date unit enumeration  
public enum DateUnit {
    MILLISECOND, SECOND, MINUTE, HOUR, DAY, WEEK, MONTH, YEAR
}

// HTTP method enumeration
public enum Method {
    GET, POST, PUT, DELETE, HEAD, OPTIONS, PATCH, TRACE
}

// Character encoding constants
public interface CharsetUtil {
    Charset UTF_8 = StandardCharsets.UTF_8;
    Charset GBK = Charset.forName("GBK");
    String UTF_8_NAME = "UTF-8";
}

// Enhanced Date class
public class DateTime extends Date {
    public DateTime();
    public DateTime(Date date);
    public DateTime(String dateStr, String format);
    
    public DateTime offset(DateField field, int offset);
    public String toString(String format);
    public boolean isWeekend();
}

// Dictionary implementation
public class Dict extends LinkedHashMap<String, Object> {
    public static Dict create();
    public Dict set(String key, Object value);
    public <T> T get(String key, Class<T> type);
}

// Database entity
public class Entity extends LinkedHashMap<String, Object> {
    public static Entity create();
    public Entity set(String key, Object value);
    public <T> T get(String key, Class<T> type);
}