In Java, tool classes define a set of public methods. This article will introduce the most frequently used and versatile Java tool classes in Java. The following tools and methods are ranked by usage popularity. The reference data comes from 50,000 randomly selected open source project source codes on Github.
1. org.apache.commons.io.IOUtils
closeQuietly：关闭一个IO流、socket、或者selector且不抛出异常，通常放在finally块 toString：转换IO流、 Uri、 byte[]为String copy：IO流数据复制，从输入流写到输出流中，最大支持2GB toByteArray：从输入流、URI获取byte[] write：把字节. 字符等写入输出流 toInputStream：把字符转换为输入流 readLines：从输入流中读取多行数据，返回List<String> copyLarge：同copy，支持2GB以上数据的复制 lineIterator：从输入流返回一个迭代器，根据参数要求读取的数据量，全部读取，如果数据不够，则失败
2. org.apache.commons.io.FileUtils
deleteDirectory：删除文件夹 readFileToString：以字符形式读取文件内容 deleteQueitly：删除文件或文件夹且不会抛出异常 copyFile：复制文件 writeStringToFile：把字符写到目标文件，如果文件不存在，则创建 forceMkdir：强制创建文件夹，如果该文件夹父级目录不存在，则创建父级 write：把字符写到指定文件中 listFiles：列举某个目录下的文件(根据过滤器) copyDirectory：复制文件夹 forceDelete：强制删除文件
三、org.apache.commons.lang.StringUtils
isBlank：字符串是否为空 (trim后判断) isEmpty：字符串是否为空 (不trim并判断) equals：字符串是否相等 join：合并数组为单一字符串，可传分隔符 split：分割字符串 EMPTY：返回空字符串 trimToNull：trim后为空字符串则转换为null replace：替换字符串
四、org.apache.http.util.EntityUtils
toString：把Entity转换为字符串 consume：确保Entity中的内容全部被消费。可以看到源码里又一次消费了Entity的内容，假如用户没有消费，那调用Entity 时候将会把它消费掉 toByteArray：把Entity转换为字节流 consumeQuietly：和consume一样，但不抛异常 getContentCharset：获取内容的编码
5. org.apache.commons.lang3.StringUtils
isBlank：字符串是否为空 (trim后判断) isEmpty：字符串是否为空 (不trim并判断) equals：字符串是否相等 join：合并数组为单一字符串，可传分隔符 split：分割字符串 EMPTY：返回空字符串 replace：替换字符串 capitalize：首字符大写
6. org.apache.commons.io.FilenameUtils
getExtension：返回文件后缀名 getBaseName：返回文件名，不包含后缀名 getName：返回文件全名 concat：按命令行风格组合文件路径(详见方法注释) removeExtension：删除后缀名 normalize：使路径正常化 wildcardMatch：匹配通配符 seperatorToUnix：路径分隔符改成unix系统格式的，即/ getFullPath：获取文件路径，不包括文件名 isExtension：检查文件后缀名是不是传入参数(List<String>)中的一个
Seven, org.springframework.util.StringUtils
hasText：检查字符串中是否包含文本 hasLength：检测字符串是否长度大于0 isEmpty：检测字符串是否为空（若传入为对象，则判断对象是否为null） commaDelimitedStringToArray：逗号分隔的String转换为数组 collectionToDelimitedString：把集合转为CSV格式字符串 replace 替换字符串 delimitedListToStringArray：相当于split uncapitalize：首字母小写 collectionToDelimitedCommaString：把集合转为CSV格式字符串 tokenizeToStringArray：和split基本一样，但能自动去掉空白的单词
Eight, org.apache.commons.lang.ArrayUtils
contains：是否包含某字符串 addAll：添加整个数组 clone：克隆一个数组 isEmpty：是否空数组 add：向数组添加元素 subarray：截取数组 indexOf：查找某个元素的下标 isEquals：比较数组是否相等 toObject：基础类型数据数组转换为对应的Object数组
Nine , org.apache.commons.lang.StringEscapeUtils
参考十五：org.apache.commons.lang3.StringEscapeUtils
十、org.apache.http.client.utils.URLEncodedUtils
format：格式化参数，返回一个HTTP POST或者HTTP PUT可用application/x-www-form-urlencoded字符串 parse：把String或者URI等转换为List<NameValuePair>
十1. org.apache.commons.codec.digest.DigestUtils
md5Hex：MD5加密，返回32位字符串 sha1Hex：SHA-1加密 sha256Hex：SHA-256加密 sha512Hex：SHA-512加密 md5：MD5加密，返回16位字符串
12. org.apache.commons.collections.CollectionUtils
isEmpty：是否为空 select：根据条件筛选集合元素 transform：根据指定方法处理集合元素，类似List的map() filter：过滤元素，雷瑟List的filter() find：基本和select一样 collect：和transform 差不多一样，但是返回新数组 forAllDo：调用每个元素的指定方法 isEqualCollection：判断两个集合是否一致
Thirteen, org.apache.commons.lang3.ArrayUtils
contains：是否包含某个字符串 addAll：添加整个数组 clone：克隆一个数组 isEmpty：是否空数组 add：向数组添加元素 subarray：截取数组 indexOf：查找某个元素的下标 isEquals：比较数组是否相等 toObject：基础类型数据数组转换为对应的Object数组
Fourteen, org.apache.commons.beanutils.PropertyUtils
getProperty：获取对象属性值 setProperty：设置对象属性值 getPropertyDiscriptor：获取属性描述器 isReadable：检查属性是否可访问 copyProperties：复制属性值，从一个对象到另一个对象 getPropertyDiscriptors：获取所有属性描述器 isWriteable：检查属性是否可写 getPropertyType：获取对象属性类型
15. org.apache.commons.lang3.StringEscapeUtils
unescapeHtml4：转义html escapeHtml4：反转义html escapeXml：转义xml unescapeXml：反转义xml escapeJava：转义unicode编码 escapeEcmaScript：转义EcmaScript字符 unescapeJava：反转义unicode编码 escapeJson：转义json字符 escapeXml10：转义Xml10
This is now obsolete. It is recommended to use the method in the commons-text package.
16. org.apache.commons.beanutils.BeanUtils
copyPeoperties：复制属性值，从一个对象到另一个对象 getProperty：获取对象属性值 setProperty：设置对象属性值 populate：根据Map给属性复制 copyPeoperty：复制单个值，从一个对象到另一个对象 cloneBean：克隆bean实例
Now as long as you understand the above 16 most popular tool methods, you don’t need to You no longer need to write your own tool classes, so you don’t have to reinvent the wheel. Most tool methods can be understood through their names. If you are not sure, you can look at how others use them, or check their usage online.
In addition: Tool class, according to the Alibaba development manual, if you want to use util, the package name cannot contain s, and the tool class is named XxxUtils.
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