Top 16 Most Popular Java Utility Classes and Their Common Methods

In Java, utility classes provide a set of common methods that simplify everyday programming tasks. This article lists the sixteen most popular utility classes based on analysis of 50,000 open‑source projects on GitHub, along with their frequently used methods.

org.apache.commons.io.IOUtils – Methods include closeQuietly , toString , copy , toByteArray , write , toInputStream , readLines , copyLarge , and lineIterator .

org.apache.commons.io.FileUtils – Provides deleteDirectory , readFileToString , deleteQuietly , copyFile , writeStringToFile , forceMkdir , write , listFiles , copyDirectory , and forceDelete .

org.apache.commons.lang.StringUtils – Includes isBlank , isEmpty , equals , join , split , EMPTY , trimToNull , and replace .

org.springframework.util.StringUtils – Offers hasText , hasLength , isEmpty , commaDelimitedStringToArray , collectionToDelimitedString , replace , delimitedListToStringArray , uncapitalize , collectionToDelimitedCommaString , and tokenizeToStringArray .

org.apache.commons.lang.ArrayUtils – Methods such as contains , addAll , clone , isEmpty , add , subarray , indexOf , isEquals , and toObject .

org.apache.commons.io.FilenameUtils – Provides getExtension , getBaseName , getName , concat , removeExtension , normalize , wildcardMatch , seperatorToUnix , getFullPath , and isExtension (returns a List<String> ).

org.apache.http.util.EntityUtils – Includes toString , consume , toByteArray , consumeQuietly , and getContentCharset .

org.apache.http.client.utils.URLEncodedUtils – Offers format and parse (returns a List<NameValuePair> ).

org.apache.commons.codec.digest.DigestUtils – Provides hashing methods: md5Hex , sha1Hex , sha256Hex , sha512Hex , and md5 .

org.apache.commons.collections.CollectionUtils – Methods include isEmpty , select , transform , filter , find , collect , forAllDo , and isEqualCollection .

org.apache.commons.beanutils.PropertyUtils – Functions such as getProperty , setProperty , getPropertyDescriptor , isReadable , copyProperties , getPropertyDescriptors , isWriteable , and getPropertyType .

org.apache.commons.beanutils.BeanUtils – Includes copyProperties , getProperty , setProperty , populate , copyProperty , and cloneBean .

org.apache.commons.lang3.StringEscapeUtils – Methods for escaping/unescaping HTML, XML, Java, JavaScript, and JSON, such as unescapeHtml4 , escapeHtml4 , escapeXml , unescapeXml , escapeJava , escapeEcmaScript , unescapeJava , and escapeJson . Note: this class is deprecated in favor of the commons‑text package.

The article concludes that understanding these utilities eliminates the need to write custom helper classes, encourages following naming conventions like XxxUtils , and invites readers to follow the “SouYunKu Technology Team” WeChat public account for more content.