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# Hutool Core
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Hutool Core is a comprehensive Java utility library providing extensive functionality for collections, strings, beans, dates, I/O operations, and numerous other common programming tasks. It offers over 90 utility classes with thousands of static methods designed to simplify Java development with null-safe operations, type conversions, and practical helper functions.
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## Package Information
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- **Package Name**: cn.hutool:hutool-core
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- **Package Type**: maven
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- **Language**: Java
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- **Installation**: Add to Maven `pom.xml`:
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  ```xml
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  <dependency>
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      <groupId>cn.hutool</groupId>
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      <artifactId>hutool-core</artifactId>
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      <version>5.8.40</version>
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  </dependency>
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  ```
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## Core Imports
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```java
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import cn.hutool.core.util.StrUtil;
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import cn.hutool.core.collection.CollUtil;
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import cn.hutool.core.date.DateUtil;
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import cn.hutool.core.io.FileUtil;
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import cn.hutool.core.bean.BeanUtil;
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import cn.hutool.core.convert.Convert;
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```
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## Basic Usage
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```java
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import cn.hutool.core.util.StrUtil;
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import cn.hutool.core.collection.CollUtil;
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import cn.hutool.core.date.DateUtil;
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// String utilities
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boolean isEmpty = StrUtil.isBlank("  "); // true
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String formatted = StrUtil.format("Hello {}", "World"); // "Hello World"
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// Collection utilities
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List<String> list = CollUtil.newArrayList("a", "b", "c");
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boolean hasItems = CollUtil.isNotEmpty(list); // true
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// Date utilities
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String dateStr = DateUtil.format(new Date(), "yyyy-MM-dd HH:mm:ss");
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Date parsed = DateUtil.parse("2023-01-15", "yyyy-MM-dd");
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```
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## Architecture
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Hutool Core is organized into distinct functional packages:
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- **Static Utility Pattern**: All functionality exposed through static methods in *Util classes
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- **Null-Safe Operations**: Extensive null checking throughout all utilities
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- **Type Safety**: Generic type support where applicable with safe casting utilities
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- **Builder Support**: Builder classes for complex object construction (StrBuilder, etc.)
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- **Converter System**: Unified type conversion framework with extensible converters
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- **Multi-Language Support**: Special utilities for Chinese-specific functionality (ID cards, phone numbers)
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## Capabilities
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### String Operations
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Comprehensive string manipulation, formatting, conversion, and validation utilities.
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```java { .api }
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public class StrUtil {
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    public static boolean isBlank(CharSequence str);
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    public static boolean isEmpty(CharSequence str);
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    public static String format(String template, Object... params);
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    public static String utf8Str(Object obj);
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}
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```
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[String Operations](./string-operations.md)
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### Collection Operations
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Utilities for creating, manipulating, and transforming Java collections with null-safe operations.
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```java { .api }
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public class CollUtil {
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    public static <T> boolean isEmpty(Collection<T> collection);
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    public static <T> boolean isNotEmpty(Collection<T> collection);
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    public static <T> List<T> newArrayList(T... values);
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    public static <T> Collection<T> union(Collection<T> coll1, Collection<T> coll2);
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}
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```
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[Collection Operations](./collection-operations.md)
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### Date and Time
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Date parsing, formatting, manipulation, and calendar operations with support for both legacy Date API and Java 8+ time API.
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```java { .api }
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public class DateUtil {
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    public static String format(Date date, String format);
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    public static Date parse(String dateStr, String format);
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    public static long between(Date beginDate, Date endDate, DateUnit unit);
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}
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```
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[Date and Time Operations](./date-time-operations.md)
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### Type Conversion
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Universal type conversion system supporting conversion between all common Java types.
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```java { .api }
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public class Convert {
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    public static <T> T convert(Class<T> type, Object value);
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    public static String toStr(Object value);
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    public static Integer toInt(Object value);
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    public static Boolean toBool(Object value);
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}
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```
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[Type Conversion](./type-conversion.md)
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### File and I/O Operations
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File operations, stream handling, resource management, and NIO utilities.
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```java { .api }
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public class FileUtil {
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    public static String readUtf8String(File file);
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    public static void writeUtf8String(String content, File file);
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    public static boolean exist(String path);
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    public static File copy(File src, File dest, boolean isOverride);
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}
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public class IoUtil {
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    public static long copy(InputStream in, OutputStream out);
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    public static void close(Closeable closeable);
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    public static String read(InputStream in, Charset charset);
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}
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```
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[File and I/O Operations](./file-io-operations.md)
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### Random Operations
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Random number generation, string generation, and collection element selection utilities.
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```java { .api }
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public class RandomUtil {
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    public static boolean randomBoolean();
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    public static int randomInt(int minInclude, int maxExclude);
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    public static String randomString(int length);
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    public static <T> T randomEle(List<T> list);
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}
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```
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[Random Operations](./random-operations.md)
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### XML Processing
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XML parsing, manipulation, and serialization utilities.
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```java { .api }
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public class XmlUtil {
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    public static Document readXML(String pathOrContent);
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    public static String toStr(Node doc, boolean isPretty);
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    public static Element getElementByXPath(Document doc, String expression);
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    public static String escape(String string);
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}
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```
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[XML Operations](./xml-operations.md)
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### Compression Utilities
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ZIP file compression, decompression, and archive manipulation utilities.
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```java { .api }
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public class ZipUtil {
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    public static File zip(String srcPath, String zipPath);
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    public static File unzip(String zipFilePath, String outFileDir);
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    public static byte[] gzip(String content, String charset);
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    public static String unGzip(byte[] buf, String charset);
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}
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```
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[Compression Operations](./compression-operations.md)
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### URL Processing
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URL creation, parsing, encoding, and manipulation utilities.
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```java { .api }
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public class URLUtil {
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    public static URL url(String url);
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    public static String decode(String url);
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    public static String normalize(String url);
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    public static InputStream getStream(URL url);
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}
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```
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[URL Operations](./url-operations.md)
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### Object Operations
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Object comparison, validation, cloning, and manipulation utilities.
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```java { .api }
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public class ObjectUtil {
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    public static boolean equals(Object obj1, Object obj2);
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    public static boolean isEmpty(Object obj);
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    public static <T> T defaultIfNull(T object, T defaultValue);
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    public static <T> T clone(T obj);
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}
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```
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[Object Operations](./object-operations.md)
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### Additional Utilities
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Other specialized utility classes available in Hutool Core:
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- **BeanUtil**: JavaBean manipulation, property copying, and object introspection
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- **ArrayUtil**: Array creation, manipulation, and conversion utilities with null-safe operations  
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- **NumberUtil**: Number parsing, formatting, mathematical operations, and validation utilities
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- **ReflectUtil**: Reflection utilities for class introspection, method invocation, and field access
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- **ReUtil**: Regular expression utilities for pattern matching, replacement, and extraction
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- **NetUtil**: Network utilities for IP address handling, URL operations, and network connectivity
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- **ImgUtil**: Image processing utilities for reading, writing, scaling, and format conversion
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- **HashUtil/HexUtil**: Hash generation, encoding/decoding, and basic cryptographic utilities
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- **IdcardUtil/PhoneUtil**: Specialized utilities for Chinese development (ID cards, phone numbers)
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## Common Types
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```java { .api }
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// Date unit enumeration
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public enum DateUnit {
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    MS, SECOND, MINUTE, HOUR, DAY, WEEK
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}
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// Charset utilities
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public class CharsetUtil {
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    public static final Charset UTF_8 = StandardCharsets.UTF_8;
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    public static final Charset GBK = Charset.forName("GBK");
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}
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// String pool constants
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public interface StrPool {
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    String EMPTY = "";
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    String NULL = "null";
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    String SPACE = " ";
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    String TAB = "\t";
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    String DOT = ".";
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    String SLASH = "/";
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    String BACKSLASH = "\\";
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}
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```