In Java, a utility class is a class that defines a set of methods that perform common functions. This post shows the most frequently used Java utility classes and their most commonly used methods. Both the class list and their method list are ordered by popularity. The data is based on randomly selected 50,000 open source Java projects from GitHub.

Hopefully, you can get a basic idea of what are already provided and popular by browsing the list so that you know you don‘t need to program it by yourself. The names of the methods normally indicate their functions. You may also click on the methods to see how they are used in open source projects.

1. org.apache.commons.io.IOUtils

• closeQuietly ( )
• toString ( )
• copy ( )
• toByteArray ( )
• write ( )
• toInputStream ( )
• readLines ( )
• copyLarge ( )
• lineIterator ( )
• readFully ( )

2. org.apache.commons.io.FileUtils

• deleteDirectory ( )
• readFileToString ( )
• deleteQuietly ( )
• copyFile ( )
• writeStringToFile ( )
• forceMkdir ( )
• write ( )
• listFiles ( )
• copyDirectory ( )
• forceDelete ( )

3. org.apache.commons.lang.StringUtils

• isBlank ( )
• isNotBlank ( )
• isEmpty ( )
• isNotEmpty ( )
• equals ( )
• join ( )
• split ( )
• EMPTY
• trimToNull ( )
• replace ( )

4. org.apache.http.util.EntityUtils

• toString ( )
• consume ( )
• toByteArray ( )
• consumeQuietly ( )
• getContentCharSet ( )

5. org.apache.commons.lang3.StringUtils

• isBlank ( )
• isNotBlank ( )
• isEmpty ( )
• isNotEmpty ( )
• join ( )
• equals ( )
• split ( )
• EMPTY
• replace ( )
• capitalize ( )

6. org.apache.commons.io.FilenameUtils

• getExtension ( )
• getBaseName ( )
• getName ( )
• concat ( )
• removeExtension ( )
• normalize ( )
• wildcardMatch ( )
• separatorsToUnix ( )
• getFullPath ( )
• isExtension ( )

7. org.springframework.util.StringUtils

• hasText ( )
• hasLength ( )
• isEmpty ( )
• commaDelimitedListToStringArray ( )
• collectionToDelimitedString ( )
• replace ( )
• delimitedListToStringArray ( )
• uncapitalize ( )
• collectionToCommaDelimitedString ( )
• tokenizeToStringArray ( )

8. org.apache.commons.lang.ArrayUtils

• contains ( )
• addAll ( )
• clone ( )
• isEmpty ( )
• add ( )
• EMPTY_BYTE_ARRAY
• subarray ( )
• indexOf ( )
• isEquals ( )
• toObject ( )

9. org.apache.commons.lang.StringEscapeUtils

• escapeHtml ( )
• unescapeHtml ( )
• escapeXml ( )
• escapeSql ( )
• unescapeJava ( )
• escapeJava ( )
• escapeJavaScript ( )
• unescapeXml ( )
• unescapeJavaScript ( )

10. org.apache.http.client.utils.URLEncodedUtils

• format ( )
• parse ( )

11. org.apache.commons.codec.digest.DigestUtils

• md5Hex ( )
• shaHex ( )
• sha256Hex ( )
• sha1Hex ( )
• sha ( )
• md5 ( )
• sha512Hex ( )
• sha1 ( )

12. org.apache.commons.collections.CollectionUtils

• isEmpty ( )
• isNotEmpty ( )
• select ( )
• transform ( )
• filter ( )
• find ( )
• collect ( )
• forAllDo ( )
• addAll ( )
• isEqualCollection ( )

13. org.apache.commons.lang3.ArrayUtils

• contains ( )
• isEmpty ( )
• isNotEmpty ( )
• add ( )
• clone ( )
• addAll ( )
• subarray ( )
• indexOf ( )
• EMPTY_OBJECT_ARRAY
• EMPTY_STRING_ARRAY

14. org.apache.commons.beanutils.PropertyUtils

• getProperty ( )
• setProperty ( )
• getPropertyDescriptors ( )
• isReadable ( )
• copyProperties ( )
• getPropertyDescriptor ( )
• getSimpleProperty ( )
• isWriteable ( )
• setSimpleProperty ( )
• getPropertyType ( )

15. org.apache.commons.lang3.StringEscapeUtils

• unescapeHtml4 ( )
• escapeHtml4 ( )
• escapeXml ( )
• unescapeXml ( )
• escapeJava ( )
• escapeEcmaScript ( )
• unescapeJava ( )
• escapeJson ( )
• escapeXml10 ( )

16. org.apache.commons.beanutils.BeanUtils

• copyProperties ( )
• getProperty ( )
• setProperty ( )
• describe ( )
• populate ( )
• copyProperty ( )
• cloneBean ( )

* The utility classes from android are excluded since they are designed for Android apps. If you want to see more details, you can search "utils" in the search portal: http://www.programcreek.com/java-api-examples/index.php. If the name of a utility class does not contain "utils", the class is not selected.

Also org.apache.commons.lang is the old version of import org.apache.commons.lang3.

Top 15 Java Utility Classes