Top 500 Java Classes

This is the index of popular classes provided by Java Stand Library, Eclipse, Apache, Spring, Android, etc. The number in "( )" indicates their popularity which scales from 1 - 3000. The numbers are based on a random sample of 3000 open source projects.
1. java.util.List     (2889)
2. java.util.ArrayList     (2831)
3. java.io.IOException     (2813)
4. java.util.Map     (2592)
5. java.util.HashMap     (2541)
6. java.io.File     (2195)
7. java.io.InputStream     (2125)
8. java.util.Arrays     (2068)
9. java.util.Collections     (2028)
10. java.util.Set     (2019)
11. java.util.Iterator     (1954)
12. java.util.Collection     (1734)
13. java.util.HashSet     (1721)
14. java.util.Date     (1679)
15. java.net.URL     (1548)
16. java.io.FileInputStream     (1495)
17. org.junit.Test     (1463)
18. java.io.BufferedReader     (1432)
19. java.io.OutputStream     (1391)
20. java.io.InputStreamReader     (1389)
21. java.io.FileOutputStream     (1378)
22. java.util.regex.Pattern     (1314)
23. java.io.FileNotFoundException     (1294)
24. java.io.Serializable     (1257)
25. java.lang.reflect.Method     (1229)
26. java.io.ByteArrayOutputStream     (1206)
27. java.util.LinkedList     (1194)
28. java.util.Properties     (1157)
29. java.text.SimpleDateFormat     (1103)
30. java.io.ByteArrayInputStream     (1079)
31. java.util.regex.Matcher     (1064)
32. java.io.UnsupportedEncodingException     (1047)
33. java.util.Locale     (1009)
34. java.util.Comparator     (1007)
35. org.junit.Before     (1005)
36. java.util.Enumeration     (949)
37. java.io.PrintWriter     (931)
38. java.util.Random     (928)
39. java.lang.reflect.InvocationTargetException     (918)
40. java.net.MalformedURLException     (916)
41. java.util.Map.Entry     (899)
42. java.util.Calendar     (859)
43. java.io.StringWriter     (819)
44. java.lang.reflect.Field     (790)
45. java.util.LinkedHashMap     (788)
46. java.net.URI     (781)
47. junit.framework.TestCase     (720)
48. java.io.Reader     (717)
49. java.io.Writer     (706)
50. java.util.concurrent.TimeUnit     (699)
51. java.io.FileReader     (691)
52. java.io.FileWriter     (682)
53. java.io.StringReader     (680)
54. java.util.logging.Logger     (677)
55. java.lang.reflect.Constructor     (664)
56. java.text.ParseException     (649)
57. java.net.URISyntaxException     (644)
58. javax.servlet.http.HttpServletRequest     (636)
59. java.lang.annotation.Retention     (635)
60. java.util.TreeSet     (632)
61. org.slf4j.Logger     (627)
62. java.util.concurrent.ConcurrentHashMap     (625)
63. java.io.OutputStreamWriter     (622)
64. java.util.TreeMap     (621)
65. java.util.StringTokenizer     (619)
66. org.slf4j.LoggerFactory     (618)
67. java.text.DateFormat     (607)
68. android.os.Bundle     (605)
69. org.junit.After     (605)
70. javax.servlet.http.HttpServletResponse     (603)
71. android.content.Context     (603)
72. java.io.BufferedInputStream     (600)
73. java.security.NoSuchAlgorithmException     (592)
74. java.util.logging.Level     (589)
75. java.lang.annotation.Target     (588)
76. java.util.concurrent.Executors     (588)
77. org.xml.sax.SAXException     (586)
78. android.util.Log     (583)
79. java.util.Vector     (583)
80. android.content.Intent     (578)
81. org.junit.runner.RunWith     (577)
82. android.app.Activity     (575)
83. javax.servlet.ServletException     (568)
84. android.view.View     (567)
85. java.lang.annotation.RetentionPolicy     (559)
86. java.util.Hashtable     (559)
87. java.security.MessageDigest     (553)
88. junit.framework.Assert     (548)
89. org.junit.Assert     (548)
90. java.io.PrintStream     (546)
91. java.net.InetAddress     (537)
92. java.util.UUID     (526)
93. android.widget.TextView     (524)
94. java.net.URLEncoder     (521)
95. org.w3c.dom.Document     (521)
96. java.lang.annotation.ElementType     (520)
97. java.net.UnknownHostException     (518)
98. java.nio.charset.Charset     (516)
99. java.io.BufferedWriter     (513)
100. java.util.concurrent.ExecutorService     (503)
101. javax.xml.parsers.DocumentBuilderFactory     (487)
102. java.nio.ByteBuffer     (481)
103. java.io.ObjectInputStream     (481)
104. java.util.concurrent.atomic.AtomicInteger     (467)
105. java.io.ObjectOutputStream     (467)
106. android.widget.Toast     (466)
107. java.util.NoSuchElementException     (466)
108. org.w3c.dom.Element     (463)
109. java.util.LinkedHashSet     (461)
110. java.io.BufferedOutputStream     (461)
111. java.math.BigInteger     (459)
112. android.os.Handler     (451)
113. org.junit.BeforeClass     (450)
114. android.content.SharedPreferences     (449)
115. android.content.DialogInterface     (449)
116. android.view.ViewGroup     (444)
117. java.math.BigDecimal     (443)
118. java.lang.reflect.Modifier     (441)
119. android.net.Uri     (437)
120. javax.xml.parsers.ParserConfigurationException     (437)
121. java.net.Socket     (436)
122. android.app.AlertDialog     (436)
123. org.w3c.dom.NodeList     (428)
124. java.util.Stack     (428)
125. android.widget.Button     (428)
126. javax.xml.parsers.DocumentBuilder     (427)
127. java.net.URLConnection     (426)
128. android.view.LayoutInflater     (423)
129. org.w3c.dom.Node     (422)
130. java.util.TimeZone     (422)
131. java.sql.SQLException     (421)
132. android.widget.ListView     (406)
133. org.xml.sax.InputSource     (405)
134. org.apache.log4j.Logger     (398)
135. android.view.MenuItem     (394)
136. android.widget.ImageView     (394)
137. org.apache.http.HttpResponse     (389)
138. org.apache.http.impl.client.DefaultHttpClient     (388)
139. java.net.HttpURLConnection     (387)
140. org.junit.Ignore     (386)
141. java.net.InetSocketAddress     (385)
142. android.util.AttributeSet     (383)
143. java.lang.reflect.Array     (383)
144. android.view.View.OnClickListener     (380)
145. android.widget.AdapterView     (376)
146. android.widget.EditText     (374)
147. android.database.Cursor     (374)
148. android.view.Menu     (374)
149. android.graphics.Bitmap     (372)
150. java.io.DataInputStream     (366)
151. java.io.DataOutputStream     (362)
152. java.util.zip.ZipEntry     (357)
153. android.widget.LinearLayout     (354)
154. javax.servlet.http.HttpServlet     (352)
155. java.text.DecimalFormat     (350)
156. java.util.concurrent.Callable     (350)
157. org.apache.commons.lang.StringUtils     (349)
158. java.io.FilenameFilter     (346)
159. java.util.GregorianCalendar     (346)
160. java.text.MessageFormat     (344)
161. java.awt.Color     (340)
162. android.view.KeyEvent     (337)
163. java.lang.annotation.Annotation     (336)
164. java.net.URLDecoder     (336)
165. java.util.concurrent.Future     (335)
166. android.graphics.drawable.Drawable     (332)
167. android.content.res.Resources     (331)
168. java.util.concurrent.atomic.AtomicBoolean     (329)
169. android.preference.PreferenceManager     (328)
170. android.widget.ArrayAdapter     (327)
171. android.view.MotionEvent     (326)
172. org.apache.commons.logging.Log     (325)
173. java.util.ResourceBundle     (324)
174. android.app.Dialog     (324)
175. org.apache.commons.logging.LogFactory     (321)
176. java.util.concurrent.ExecutionException     (320)
177. java.lang.ref.WeakReference     (320)
178. android.graphics.Canvas     (319)
179. java.sql.ResultSet     (319)
180. android.os.AsyncTask     (317)
181. org.apache.http.client.methods.HttpGet     (317)
182. java.sql.Connection     (317)
183. java.util.Queue     (315)
184. java.io.Closeable     (313)
185. android.content.ContentValues     (311)
186. java.util.ListIterator     (311)
187. android.content.BroadcastReceiver     (307)
188. org.apache.commons.io.IOUtils     (305)
189. android.content.pm.PackageManager     (301)
190. android.preference.PreferenceActivity     (299)
191. org.junit.AfterClass     (299)
192. android.os.Message     (296)
193. android.graphics.Color     (295)
194. java.net.ServerSocket     (295)
195. org.json.JSONObject     (294)
196. org.apache.http.client.HttpClient     (292)
197. java.util.TimerTask     (291)
198. java.util.concurrent.CountDownLatch     (289)
199. android.app.ProgressDialog     (287)
200. java.awt.event.ActionEvent     (287)
201. javax.servlet.ServletContext     (285)
202. android.view.Window     (285)
203. java.util.Timer     (285)
204. android.graphics.BitmapFactory     (281)
205. android.database.sqlite.SQLiteDatabase     (278)
206. java.awt.image.BufferedImage     (276)
207. android.os.IBinder     (276)
208. java.lang.reflect.Type     (275)
209. java.util.SortedSet     (274)
210. android.content.ComponentName     (273)
211. java.text.NumberFormat     (272)
212. android.app.PendingIntent     (271)
213. java.awt.event.ActionListener     (269)
214. org.osgi.framework.BundleContext     (269)
215. java.util.concurrent.LinkedBlockingQueue     (267)
216. java.util.concurrent.atomic.AtomicLong     (267)
217. android.text.TextUtils     (267)
218. org.json.JSONException     (265)
219. org.apache.commons.io.FileUtils     (264)
220. javax.servlet.ServletRequest     (263)
221. org.apache.http.HttpEntity     (263)
222. android.widget.BaseAdapter     (263)
223. android.os.Build     (263)
224. java.util.zip.GZIPInputStream     (260)
225. java.awt.Dimension     (259)
226. org.xml.sax.Attributes     (258)
227. android.widget.AdapterView.OnItemClickListener     (257)
228. android.os.Environment     (257)
229. java.util.concurrent.CopyOnWriteArrayList     (256)
230. java.io.FileFilter     (255)
231. javax.xml.transform.stream.StreamResult     (255)
232. android.app.Service     (253)
233. android.app.ListActivity     (252)
234. android.view.Gravity     (251)
235. javax.swing.JPanel     (251)
236. javax.swing.JFrame     (250)
237. javax.servlet.ServletResponse     (249)
238. android.database.sqlite.SQLiteOpenHelper     (249)
239. java.security.SecureRandom     (248)
240. android.graphics.Rect     (247)
241. junit.framework.Test     (246)
242. java.net.URLClassLoader     (245)
243. junit.framework.TestSuite     (245)
244. android.graphics.Paint     (245)
245. org.apache.http.client.methods.HttpPost     (244)
246. java.util.concurrent.BlockingQueue     (243)
247. java.util.concurrent.ConcurrentMap     (242)
248. javax.imageio.ImageIO     (241)
249. android.content.pm.PackageManager.NameNotFoundException     (241)
250. java.util.EnumSet     (238)
251. java.nio.channels.FileChannel     (236)
252. javax.xml.transform.TransformerFactory     (236)
253. java.util.concurrent.locks.ReentrantLock     (236)
254. android.view.WindowManager     (234)
255. android.content.ContentResolver     (234)
256. java.sql.PreparedStatement     (234)
257. org.json.JSONArray     (234)
258. javax.inject.Inject     (233)
259. android.content.IntentFilter     (233)
260. java.util.WeakHashMap     (233)
261. javax.swing.JLabel     (232)
262. java.net.SocketException     (232)
263. javax.xml.transform.Transformer     (231)
264. android.view.ContextMenu     (229)
265. javax.servlet.http.HttpSession     (228)
266. java.lang.reflect.Proxy     (228)
267. java.io.EOFException     (227)
268. java.sql.Statement     (226)
269. android.widget.ImageButton     (222)
270. java.io.RandomAccessFile     (220)
271. android.content.res.Configuration     (220)
272. javax.sql.DataSource     (219)
273. android.widget.CheckBox     (217)
274. com.google.common.collect.Lists     (216)
275. android.app.Application     (215)
276. org.xml.sax.helpers.DefaultHandler     (214)
277. java.util.concurrent.atomic.AtomicReference     (214)
278. javax.xml.transform.dom.DOMSource     (213)
279. javax.persistence.Entity     (213)
280. android.preference.Preference     (213)
281. android.app.Notification     (212)
282. org.codehaus.jackson.map.ObjectMapper     (212)
283. javax.swing.JOptionPane     (212)
284. android.os.SystemClock     (212)
285. org.springframework.beans.factory.annotation.Autowired     (211)
286. java.lang.reflect.InvocationHandler     (211)
287. javax.servlet.FilterChain     (210)
288. java.util.SortedMap     (209)
289. android.os.Parcelable     (207)
290. android.app.NotificationManager     (207)
291. org.springframework.context.ApplicationContext     (204)
292. javax.persistence.Id     (203)
293. android.view.MenuInflater     (203)
294. java.awt.BorderLayout     (203)
295. android.widget.ProgressBar     (202)
296. java.awt.event.MouseEvent     (202)
297. java.sql.DriverManager     (201)
298. org.apache.http.params.HttpParams     (201)
299. android.graphics.Typeface     (200)
300. java.util.jar.JarFile     (200)
301. java.util.concurrent.ThreadFactory     (199)
302. java.awt.Component     (196)
303. android.graphics.drawable.BitmapDrawable     (195)
304. java.util.concurrent.Executor     (194)
305. java.lang.reflect.ParameterizedType     (194)
306. javax.servlet.Filter     (192)
307. javax.servlet.FilterConfig     (192)
308. javax.swing.JButton     (192)
309. android.content.pm.PackageInfo     (191)
310. java.util.concurrent.TimeoutException     (190)
311. java.util.Scanner     (188)
312. org.apache.commons.codec.binary.Base64     (188)
313. android.widget.FrameLayout     (188)
314. java.util.jar.JarEntry     (187)
315. java.util.zip.ZipFile     (187)
316. java.awt.Graphics2D     (186)
317. java.awt.Font     (186)
318. java.awt.Graphics     (185)
319. java.lang.ref.SoftReference     (185)
320. java.security.cert.X509Certificate     (184)
321. java.security.Principal     (184)
322. javax.naming.NamingException     (184)
323. android.webkit.WebView     (183)
324. android.view.animation.Animation     (183)
325. android.content.res.TypedArray     (181)
326. java.util.concurrent.locks.Lock     (181)
327. javax.xml.parsers.SAXParserFactory     (181)
328. javax.swing.JScrollPane     (181)
329. org.testng.annotations.Test     (180)
330. java.util.concurrent.ScheduledExecutorService     (179)
331. java.util.MissingResourceException     (178)
332. android.view.ContextMenu.ContextMenuInfo     (178)
333. javax.xml.transform.TransformerException     (178)
334. com.google.common.collect.Maps     (178)
335. android.content.ActivityNotFoundException     (177)
336. android.widget.CompoundButton     (177)
337. android.os.Parcel     (176)
338. javax.net.ssl.SSLContext     (175)
339. android.view.animation.AnimationUtils     (174)
340. org.apache.http.Header     (174)
341. android.content.pm.ResolveInfo     (172)
342. java.security.cert.CertificateException     (171)
343. java.sql.Timestamp     (171)
344. java.security.AccessController     (171)
345. java.awt.event.WindowEvent     (171)
346. android.content.SharedPreferences.Editor     (170)
347. java.awt.event.KeyEvent     (169)
348. android.graphics.RectF     (169)
349. android.view.ViewGroup.LayoutParams     (169)
350. org.w3c.dom.NamedNodeMap     (169)
351. java.lang.management.ManagementFactory     (168)
352. org.xmlpull.v1.XmlPullParserException     (168)
353. javax.servlet.http.Cookie     (168)
354. android.os.Looper     (166)
355. org.xmlpull.v1.XmlPullParser     (166)
356. java.util.concurrent.locks.ReentrantReadWriteLock     (166)
357. javax.xml.bind.annotation.XmlRootElement     (166)
358. java.util.concurrent.ConcurrentLinkedQueue     (164)
359. android.widget.ListAdapter     (164)
360. javax.swing.JTextField     (164)
361. java.util.BitSet     (163)
362. javax.xml.parsers.SAXParser     (163)
363. java.util.concurrent.ThreadPoolExecutor     (163)
364. javax.servlet.ServletConfig     (163)
365. java.util.zip.ZipInputStream     (162)
366. android.net.ConnectivityManager     (162)
367. java.beans.PropertyChangeListener     (161)
368. org.osgi.framework.Bundle     (159)
369. javax.naming.InitialContext     (159)
370. java.awt.Image     (158)
371. org.apache.http.params.BasicHttpParams     (158)
372. javax.persistence.EntityManager     (158)
373. java.util.zip.ZipOutputStream     (157)
374. java.security.PrivilegedAction     (157)
375. java.nio.CharBuffer     (157)
376. javax.swing.ImageIcon     (157)
377. java.beans.PropertyDescriptor     (157)
378. javax.xml.bind.JAXBContext     (153)
379. com.google.common.base.Function     (153)
380. javax.management.ObjectName     (153)
381. org.apache.http.client.ClientProtocolException     (152)
382. android.widget.Spinner     (152)
383. android.content.DialogInterface.OnClickListener     (152)
384. javax.persistence.GeneratedValue     (151)
385. javax.swing.SwingUtilities     (151)
386. javax.xml.namespace.QName     (151)
387. android.os.RemoteException     (150)
388. org.eclipse.swt.SWT     (150)
389. android.text.Editable     (150)
390. org.eclipse.swt.widgets.Composite     (149)
391. org.mockito.Mockito     (149)
392. org.springframework.core.io.Resource     (149)
393. android.content.ContentProvider     (149)
394. android.graphics.Matrix     (149)
395. android.widget.RelativeLayout     (148)
396. javax.servlet.ServletOutputStream     (148)
397. com.google.common.collect.Sets     (147)
398. org.apache.http.message.BasicNameValuePair     (147)
399. java.util.EventListener     (147)
400. javax.xml.transform.OutputKeys     (146)
401. java.awt.Point     (146)
402. java.beans.PropertyChangeEvent     (146)
403. android.provider.BaseColumns     (145)
404. javax.swing.JComponent     (145)
405. org.apache.http.NameValuePair     (144)
406. javax.swing.BorderFactory     (144)
407. org.joda.time.DateTime     (144)
408. javax.persistence.Column     (144)
409. javax.ws.rs.Path     (143)
410. org.apache.http.util.EntityUtils     (143)
411. java.io.DataInput     (143)
412. javax.annotation.PostConstruct     (143)
413. org.xml.sax.XMLReader     (143)
414. org.apache.http.params.HttpConnectionParams     (142)
415. org.junit.Rule     (142)
416. org.apache.commons.httpclient.HttpClient     (142)
417. javax.xml.bind.annotation.XmlElement     (142)
418. android.util.DisplayMetrics     (141)
419. javax.xml.transform.stream.StreamSource     (141)
420. android.media.AudioManager     (140)
421. android.content.pm.ActivityInfo     (140)
422. org.eclipse.ui.plugin.AbstractUIPlugin     (139)
423. com.google.inject.Inject     (139)
424. java.security.KeyStore     (139)
425. org.springframework.test.context.ContextConfiguration     (139)
426. com.google.common.base.Preconditions     (139)
427. javax.net.ssl.TrustManager     (139)
428. javax.naming.Context     (138)
429. org.apache.hadoop.conf.Configuration     (138)
430. java.io.FilterInputStream     (138)
431. org.osgi.framework.BundleActivator     (138)
432. android.view.ViewConfiguration     (138)
433. android.database.SQLException     (138)
434. javax.servlet.ServletContextEvent     (138)
435. android.util.TypedValue     (138)
436. javax.ws.rs.GET     (137)
437. android.content.ContentUris     (137)
438. java.awt.Rectangle     (137)
439. org.springframework.context.support.ClassPathXmlApplicationContext     (137)
440. org.apache.http.conn.scheme.Scheme     (136)
441. org.apache.log4j.Level     (135)
442. org.eclipse.swt.layout.GridData     (135)
443. javax.swing.JTextArea     (135)
444. org.apache.http.client.entity.UrlEncodedFormEntity     (135)
445. org.eclipse.core.runtime.IProgressMonitor     (135)
446. android.text.TextWatcher     (135)
447. java.net.SocketTimeoutException     (134)
448. org.eclipse.swt.widgets.Display     (134)
449. java.util.zip.GZIPOutputStream     (134)
450. java.util.EventObject     (134)
451. android.text.Html     (134)
452. javax.net.ssl.X509TrustManager     (133)
453. javax.ws.rs.core.MediaType     (133)
454. org.eclipse.core.runtime.CoreException     (133)
455. android.content.ServiceConnection     (132)
456. com.google.common.base.Predicate     (132)
457. javax.crypto.spec.SecretKeySpec     (132)
458. java.util.concurrent.ArrayBlockingQueue     (132)
459. javax.swing.JFileChooser     (131)
460. org.apache.http.HttpStatus     (131)
461. org.xml.sax.SAXParseException     (130)
462. java.awt.Insets     (130)
463. android.os.PowerManager     (130)
464. javax.ws.rs.Produces     (130)
465. javax.management.MBeanServer     (129)
466. javax.swing.UIManager     (129)
467. org.eclipse.swt.layout.GridLayout     (129)
468. java.io.DataOutput     (128)
469. org.eclipse.swt.widgets.Label     (128)
470. org.apache.http.impl.conn.tsccm.ThreadSafeClientConnManager     (128)
471. org.apache.http.protocol.HttpContext     (128)
472. java.nio.ByteOrder     (128)
473. javax.crypto.Cipher     (128)
474. java.awt.Toolkit     (128)
475. android.net.NetworkInfo     (127)
476. java.awt.event.WindowAdapter     (127)
477. com.google.inject.Injector     (127)
478. org.apache.http.conn.scheme.SchemeRegistry     (126)
479. org.eclipse.swt.events.SelectionEvent     (126)
480. android.content.UriMatcher     (126)
481. org.springframework.beans.factory.InitializingBean     (125)
482. android.widget.AbsListView     (125)
483. java.awt.event.MouseAdapter     (125)
484. android.view.inputmethod.InputMethodManager     (125)
485. org.eclipse.core.runtime.IStatus     (124)
486. javax.xml.bind.JAXBException     (124)
487. org.mockito.Mock     (124)
488. java.net.ConnectException     (123)
489. org.osgi.framework.ServiceReference     (123)
490. android.support.v4.app.Fragment     (123)
491. java.beans.Introspector     (123)
492. org.springframework.stereotype.Controller     (123)
493. javax.xml.transform.Source     (123)
494. android.preference.ListPreference     (123)
495. javax.swing.JMenuItem     (123)
496. org.eclipse.core.runtime.Status     (123)
497. android.content.pm.ApplicationInfo     (123)
498. javax.xml.xpath.XPathFactory     (122)
499. java.awt.Container     (122)
500. com.google.gson.Gson     (122)