大部分的 Java 软件开发都会使用到各种不同的库。近日我们从一万个开源的 Java 项目中进行分析，从中提取出最常用的 Java 类，这些类有来自于 Java 的标准库，也有第三方库。每个类在同一个项目中只计数一次，下面的列表中显示前 100 名的类。 以下列表中按使用最多的类进行排序，第三个数值表示 10000 个项目里使用到该类的项目数，而完整的列表请看 [url=http://www.programcreek.com/java-api-examples/?action=index][i]here[/i][/url]. [list=1] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.ArrayList]java.util.ArrayList [/url](6958) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.IOException]java.io.IOException [/url](6866) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.List]java.util.List [/url](6784) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.HashMap]java.util.HashMap [/url](5590) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.Map]java.util.Map [/url](5413) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.File]java.io.File [/url](5097) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.InputStream]java.io.InputStream [/url](4234) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.Set]java.util.Set [/url](3915) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.Arrays]java.util.Arrays [/url](3884) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.Iterator]java.util.Iterator [/url](3856) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.Collections]java.util.Collections [/url](3643) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.Date]java.util.Date [/url](3461) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.HashSet]java.util.HashSet [/url](3278) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.BufferedReader]java.io.BufferedReader [/url](3257) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.Collection]java.util.Collection [/url](3192) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.net.URL]java.net.URL [/url](3168) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.FileInputStream]java.io.FileInputStream [/url](3044) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.InputStreamReader]java.io.InputStreamReader [/url](3023) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=org.junit.Test]org.junit.Test [/url](3008) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.FileOutputStream]java.io.FileOutputStream [/url](2843) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.FileNotFoundException]java.io.FileNotFoundException [/url](2669) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.OutputStream]java.io.OutputStream [/url](2563) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.regex.Pattern]java.util.regex.Pattern [/url](2469) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.Serializable]java.io.Serializable [/url](2437) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.LinkedList]java.util.LinkedList [/url](2372) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.text.SimpleDateFormat]java.text.SimpleDateFormat [/url](2245) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.Properties]java.util.Properties [/url](2190) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.Random]java.util.Random [/url](2171) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.lang.reflect.Method]java.lang.reflect.Method [/url](2141) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.ByteArrayOutputStream]java.io.ByteArrayOutputStream [/url](2112) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.regex.Matcher]java.util.regex.Matcher [/url](2012) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=android.os.Bundle]android.os.Bundle [/url](2007) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.logging.Logger]java.util.logging.Logger [/url](1999) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.UnsupportedEncodingException]java.io.UnsupportedEncodingException [/url](1968) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=org.junit.Before]org.junit.Before [/url](1920) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.Comparator]java.util.Comparator [/url](1896) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.ByteArrayInputStream]java.io.ByteArrayInputStream [/url](1868) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.PrintWriter]java.io.PrintWriter [/url](1862) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.Calendar]java.util.Calendar [/url](1854) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=android.app.Activity]android.app.Activity [/url](1843) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.net.MalformedURLException]java.net.MalformedURLException [/url](1828) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=android.content.Context]android.content.Context [/url](1780) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=android.view.View]android.view.View [/url](1731) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.Locale]java.util.Locale [/url](1719) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.Enumeration]java.util.Enumeration [/url](1709) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.Map.Entry]java.util.Map.Entry [/url](1705) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.FileWriter]java.io.FileWriter [/url](1677) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.FileReader]java.io.FileReader [/url](1651) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=android.util.Log]android.util.Log [/url](1614) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=android.content.Intent]android.content.Intent [/url](1601) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.lang.reflect.InvocationTargetException]java.lang.reflect.InvocationTargetException [/url](1594) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.logging.Level]java.util.logging.Level [/url](1557) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.lang.reflect.Field]java.lang.reflect.Field [/url](1499) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.StringWriter]java.io.StringWriter [/url](1499) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=android.widget.TextView]android.widget.TextView [/url](1442) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.LinkedHashMap]java.util.LinkedHashMap [/url](1409) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.Reader]java.io.Reader [/url](1390) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.net.URI]java.net.URI [/url](1377) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.Writer]java.io.Writer [/url](1339) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.text.ParseException]java.text.ParseException [/url](1318) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=junit.framework.TestCase]junit.framework.TestCase [/url](1318) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.OutputStreamWriter]java.io.OutputStreamWriter [/url](1295) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.StringReader]java.io.StringReader [/url](1279) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.BufferedWriter]java.io.BufferedWriter [/url](1265) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.Vector]java.util.Vector [/url](1254) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.StringTokenizer]java.util.StringTokenizer [/url](1251) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.text.DateFormat]java.text.DateFormat [/url](1246) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.concurrent.TimeUnit]java.util.concurrent.TimeUnit [/url](1237) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.BufferedInputStream]java.io.BufferedInputStream [/url](1235) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.TreeMap]java.util.TreeMap [/url](1227) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=org.xml.sax.SAXException]org.xml.sax.SAXException [/url](1218) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=javax.servlet.http.HttpServletRequest]javax.servlet.http.HttpServletRequest [/url](1175) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.io.PrintStream]java.io.PrintStream [/url](1168) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.TreeSet]java.util.TreeSet [/url](1160) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=android.widget.Toast]android.widget.Toast [/url](1157) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.Hashtable]java.util.Hashtable [/url](1154) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.lang.reflect.Constructor]java.lang.reflect.Constructor [/url](1139) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.net.URLEncoder]java.net.URLEncoder [/url](1134) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.security.NoSuchAlgorithmException]java.security.NoSuchAlgorithmException [/url](1134) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=org.w3c.dom.Document]org.w3c.dom.Document [/url](1130) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=android.widget.Button]android.widget.Button [/url](1129) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=org.junit.After]org.junit.After [/url](1128) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=javax.servlet.http.HttpServletResponse]javax.servlet.http.HttpServletResponse [/url](1109) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.awt.Color]java.awt.Color [/url](1099) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.net.URISyntaxException]java.net.URISyntaxException [/url](1085) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=javax.servlet.ServletException]javax.servlet.ServletException [/url](1081) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=javax.xml.parsers.DocumentBuilderFactory]javax.xml.parsers.DocumentBuilderFactory [/url](1076) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.lang.annotation.Retention]java.lang.annotation.Retention [/url](1075) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.security.MessageDigest]java.security.MessageDigest [/url](1072) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.concurrent.Executors]java.util.concurrent.Executors [/url](1062) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.net.UnknownHostException]java.net.UnknownHostException [/url](1057) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=org.slf4j.Logger]org.slf4j.Logger [/url](1054) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.sql.SQLException]java.sql.SQLException [/url](1043) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=org.slf4j.LoggerFactory]org.slf4j.LoggerFactory [/url](1042) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.UUID]java.util.UUID [/url](1040) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.net.InetAddress]java.net.InetAddress [/url](1026) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=junit.framework.Assert]junit.framework.Assert [/url](1011) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=android.view.ViewGroup]android.view.ViewGroup [/url](1005) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.util.concurrent.ConcurrentHashMap]java.util.concurrent.ConcurrentHashMap [/url](1001) [/*] [*] [url=http://www.programcreek.com/java-api-examples/index.php?api=java.awt.event.ActionEvent]java.awt.event.ActionEvent [/url](995) [/*] [/list] 上表中，一点也不奇怪，有 85 个是 Java 的标准库，因为这是语言本身的一部分，涉及 util、lang 和 io 包。 下图是包使用的分布图： [img]http://img.1sucai.cn/uploads/article/2018010710/20180107100136_0_2259.jpg[/img] 该调查是分析源码文件中的 import 语句，因此你并没有发现大量的 String, Math, StringBuilder 等类，所以没必要对它们进行排除。 via [url=http://www.programcreek.com/2014/09/top-100-classes-used-in-java-projects/]programcreek[/url]