{"id":907,"date":"2014-05-03T21:52:31","date_gmt":"2014-05-03T13:52:31","guid":{"rendered":"http:\/\/coderbee.net\/?p=907"},"modified":"2014-05-03T23:04:05","modified_gmt":"2014-05-03T15:04:05","slug":"java-%e6%80%a7%e8%83%bd%e8%b0%83%e4%bc%98%e6%8c%87%e5%8d%97-%e9%ab%98%e6%80%a7%e8%83%bdjava","status":"publish","type":"post","link":"https:\/\/coderbee.net\/index.php\/java\/20140503\/907","title":{"rendered":"Java \u6027\u80fd\u8c03\u4f18\u6307\u5357 &#8211; \u9ad8\u6027\u80fdJava"},"content":{"rendered":"<p>\u672c\u6587\u4e3b\u8981\u57fa\u4e8e <a href=\"http:\/\/java-performance.com\/\">Java performance tuning tips or everything you want to know about Java performance in 15 minutes<\/a>\u7684\u7ffb\u8bd1\u3002<\/p>\n<p>\u8fd9\u7bc7\u6307\u5357\u4e3b\u8981\u8c03\u4f18 java \u4ee3\u7801\u800c\u4e0d\u662f JVM \u8bbe\u7f6e\u3002<\/p>\n<h2>\u4e00\u3001JDK \u7c7b<\/h2>\n<h3><a href=\"http:\/\/java-performance.info\/changes-to-string-java-1-7-0_06\/\">Java 1.7.0_06 String \u5185\u90e8\u8868\u793a\u7684\u6539\u53d8<\/a><\/h3>\n<ul>\n<li>\u4ece Java 1.7.0_06 \u5f00\u59cb\uff0c<code>String.substring<\/code> \u603b\u662f\u4e3a\u5b83\u521b\u5efa\u7684\u65b0\u5b57\u7b26\u4e32\u521b\u5efa\u4e00\u4e2a\u65b0\u7684\u5e95\u5c42 <code>char[]<\/code>  \u503c\u3002\u8fd9\u610f\u5473\u7740\u8fd9\u4e2a\u65b9\u6cd5\u73b0\u5728\u6709\u7ebf\u6027\u7684\u590d\u6742\u5ea6\uff0c\u4e4b\u524d\u662f\u5e38\u91cf\u7684\u590d\u6742\u5ea6\u3002\u8fd9\u4e2a\u6539\u53d8\u7684\u597d\u5904\u662f\u5b57\u7b26\u4e32\u9700\u8981\u66f4\u5c11\u7684\u5185\u5b58 footprint\uff08\u6bd4\u4ee5\u524d\u5c118\u5b57\u8282\uff09\uff0c\u4e5f\u662f\u907f\u514d <code>String.substring<\/code> \u5bfc\u81f4\u7684\u5185\u5b58\u6cc4\u9732\u7684\u4e00\u4e2a\u4fdd\u8bc1\u3002<\/li>\n<\/ul>\n<h3><a href=\"http:\/\/java-performance.info\/various-methods-of-binary-serialization-in-java\/\">Java \u91cc\u4e8c\u8fdb\u5236\u5e8f\u5217\u5316\u7684\u4e0d\u540c\u65b9\u6cd5<\/a><\/h3>\n<ul>\n<li>\u5199\u5355\u4e2a\u5b57\u8282\u5230\u76f4\u63a5\u5b57\u8282\u7f13\u5b58\u662f\u975e\u5e38\u6162\u7684\u3002\u5bf9\u5199\u8bb0\u5f55 &#8212; \u5927\u591a\u6570\u60c5\u51b5\u662f\u5355\u4e2a\u5b57\u8282\u7684\u5b57\u6bb5\uff0c\u4f60\u5e94\u8be5\u907f\u514d\u4f7f\u7528\u76f4\u63a5\u5b57\u8282\u7f13\u5b58\u3002<\/li>\n<li>\u5982\u679c\u4f60\u6709\u539f\u59cb\u6570\u7ec4\u5b57\u6bb5\uff0c\u603b\u662f\u4f7f\u7528bulk\u65b9\u6cd5\u6765\u5904\u7406\u5b83\u4eec\uff08\u4e00\u6b21\u5904\u7406\u4e00\u6279\u7684\uff09\u3002ByteBuffer \u7684bulk \u65b9\u6cd5\u7684\u6027\u80fd\u63a5\u8fd1\u4e8eUnsafe\u7684\u8fd9\u4e9b\u65b9\u6cd5\u3002\u5982\u679c\u4f60\u9700\u8981\u5b58\u50a8\/\u52a0\u8f7d\u4efb\u4f55\u5176\u5b83\u539f\u59cb\u6570\u7ec4 &#8211; \u9664\u5b57\u8282\u578b\u7684\uff0c\u7528 <code>ByteBuffer.to[YouType]Buffer.put(array)<\/code> \u65b9\u6cd5\u8c03\u7528\uff0c\u5b57\u8282\u7f13\u5b58\u7684\u4f4d\u7f6e\u4f1a\u81ea\u52a8\u66f4\u65b0\u3002\u4e0d\u8981\u5728\u5faa\u73af\u91cc\u8c03\u7528 <code>ByteBuffer.put[YouType]<\/code> \u65b9\u6cd5\u3002<\/li>\n<li>\u603b\u662f\u5c1d\u8bd5\u7528\u5e26\u672c\u5730\u5b57\u8282\u987a\u5e8f\u7684\u76f4\u63a5\u7f13\u5b58\u5e8f\u5217\u5316\u539f\u59cb\u6570\u7ec4\u3002\u76f4\u63a5\u5b57\u8282\u7f13\u5b58\u7684\u6027\u80fd\u63a5\u8fd1\u4e8eUnsafe\u4e14\u662f\u53ef\u79fb\u690d\u7684\u3002<\/li>\n<\/ul>\n<h3><a href=\"http:\/\/java-performance.info\/java-collections-overview\/\">Java \u96c6\u5408\u6982\u89c8<\/a><\/h3>\n<table>\n<tr>\n<td><\/td>\n<td>\u5355\u7ebf\u7a0b<\/td>\n<td>\u5e76\u53d1<\/td>\n<\/tr>\n<tr>\n<td>Lists<\/td>\n<td>ArrayList \uff1a \u4e00\u822c\u57fa\u4e8e\u6570\u7ec4<br \/>LinkedList \uff1a\u4e0d\u8981\u4f7f\u7528<br \/>Vector\uff1a\u5e9f\u5f03<\/td>\n<td>CopyOnWriteArrayList\uff1a\u5f88\u5c11\u66f4\u65b0\uff0c\u7ecf\u5e38\u904d\u5386\u3002<\/td>\n<\/tr>\n<tr>\n<td>Queues\/deques<\/td>\n<td>ArrayDeque\uff1a\u4e00\u822c\u57fa\u4e8e\u6570\u7ec4\u3002<br \/>Stack\uff1a\u5e9f\u5f03\u3002<br \/>PriorityQueue\uff1a\u6709\u5e8f\u7684\u68c0\u7d22\u64cd\u4f5c\u3002<\/td>\n<td>ArrayBlockQueue\uff1a\u6709\u754c\u963b\u585equeue\u3002<br \/>ConcurrentLinkedDeque\/ConcurrentLinkedQueue\uff1a\u65e0\u754c\u94fe\u63a5queue\uff08CAS\uff09\u3002<br \/>DelayQueue\uff1a\u5728\u6bcf\u4e2a\u5143\u7d20\u4e0a\u5e26\u5ef6\u8fdf\u7684queue\u3002<br \/>LinkedBlockingDeque\/LinkedBlockingQueue\uff1a\u53ef\u9009\u7684\u6709\u754c\u94fe\u63a5queue\uff08\u9501\uff09\u3002<br \/>LinkedTransferQueue\uff1amay transfer elements w\/o storing\u3002<br \/>PriorityBlockingQueue\uff1a\u5e76\u53d1\u7684PriorityQueue\u3002<br \/>SynchronousQueue\uff1a\u5b9e\u73b0\u4e86Queue\u63a5\u53e3\u7684Exchanger\u3002<\/td>\n<\/tr>\n<tr>\n<td>Maps<\/td>\n<td>HashMap\uff1a\u4e00\u822c\u7684map\u3002<br \/>EnumMap\uff1aenum\u4f5c\u4e3akey\u7684\u3002Hashtable\uff1a\u5e9f\u5f03\u3002<br \/>IdentityHashMap\uff1a\u7528 == \u6bd4\u8f83\u952e\u3002<br \/>LinkedHashMap\uff1a\u4fdd\u7559\u4e86\u63d2\u5165\u987a\u5e8f\u3002<br \/>TreeMap\uff1a\u6709\u5e8f\u7684\u952e\u3002<br \/>WeakHashMap\uff1a\u53ef\u7528\u4e8e\u7f13\u5b58\u3002<\/td>\n<td>ConcurrentHashMap\uff1a\u4e00\u822c\u7684\u5e76\u53d1map\u3002<br \/>ConcurrentSkipListMap\uff1a\u6709\u5e8f\u7684\u5e76\u53d1map\u3002<\/td>\n<\/tr>\n<tr>\n<td>Sets<\/td>\n<td>HashSet\uff1a\u4e00\u822c\u7684set\u3002<br \/>EnumSet\uff1aenum\u7684\u96c6\u5408\u3002<br \/>BitSet\uff1a\u6bd4\u7279\u4f4d\u6216\u7a00\u758f\u6574\u6570\u7684\u96c6\u5408\u3002<br \/>LinkedHashSet\uff1a\u4fdd\u7559\u4e86\u63d2\u5165\u987a\u5e8f\u3002<br \/>TreeSet\uff1a\u6709\u5e8f\u96c6\u5408\u3002<\/td>\n<td>ConcurrentSkipListSet\uff1a\u6709\u5e8f\u5e76\u53d1\u96c6\u5408\u3002<br \/>CopyOnWriteArraySet\uff1a\u5f88\u5c11\u66f4\u65b0\uff0c\u7ecf\u5e38\u904d\u5386\u3002<\/td>\n<\/tr>\n<\/table>\n<p><!--more--><\/p>\n<h3><a href=\"http:\/\/java-performance.info\/arraylist-performance\/\">ArrayList \u6027\u80fd\u6307\u5357<\/a><\/h3>\n<p>\u4f7f\u7528ArrayList\u65f6\u9075\u5faa\u4e0b\u9762\u7684\u89c4\u5219\uff1a<\/p>\n<ul>\n<li>\u6dfb\u52a0\u5143\u7d20\u5230\u5217\u8868\u7684\u672b\u5c3e\u3002<\/li>\n<li>\u4ece\u672b\u5c3e\u5220\u9664\u5143\u7d20\u3002<\/li>\n<li>\u907f\u514d <code>contains, indexOf, remove(object)<\/code> \u65b9\u6cd5\u3002<\/li>\n<li>\u751a\u81f3\u907f\u514d <code>removeAll, retainAll<\/code> \u65b9\u6cd5\u3002<\/li>\n<li>\u4f7f\u7528 <code>subList(int, int).clear()<\/code> \u6765\u5feb\u901f\u6e05\u9664\u5217\u8868\u7684\u90e8\u5206\u3002<\/li>\n<\/ul>\n<h3><a href=\"http:\/\/java-performance.info\/linkedlist-performance\/\">LinkedList \u6027\u80fd<\/a><\/h3>\n<p>\u5982\u679c\u4f60\u9700\u8981\u5199\u4e00\u4e2a\u5feb\u901f\u7684 LinkedList \u4ee3\u7801\uff0c\u5c1d\u8bd5\u575a\u6301\u8fd9\u4e9b\u89c4\u5219\uff1a<br \/>\n*   \u8003\u8651\u7528 ArrayDeque \u7528\u4e8e\u57fa\u4e8e queue\u7684\u7b97\u6cd5\u3002<br \/>\n*   \u4e0e LinkedList \u4e00\u8d77\u4f7f\u7528 ListIterator\u3002<br \/>\n*   \u907f\u514d\u4efb\u4f55\u63a5\u53d7\u6216\u8fd4\u56de\u5143\u7d20\u5728\u5217\u8868\u91cc\u7684\u4e0b\u6807\u7684 LinkedList \u65b9\u6cd5\u3002\uff08\u57fa\u4e8e\u94fe\u8868\u7684\u5217\u8868\u4e0d\u9002\u5408\u968f\u673a\u68c0\u7d22\uff09<br \/>\n*   \u5982\u679c\u4f60\u6709\u7406\u7531\u4f7f\u7528 <code>LinkedList.remove\/removeFirst\/removeLast<\/code> \u5219\u68c0\u67e5\uff0c\u7528 <code>pollFirst\/pollLast<\/code> \u66ff\u4ee3\u3002<br \/>\n*   \u5c1d\u8bd5\u6279\u5904\u7406 LinkedList\u3002<\/p>\n<h3><a href=\"http:\/\/java-performance.info\/bit-sets\/\">Bit sets<\/a><\/h3>\n<ul>\n<li>\u5f53\u4f60\u9700\u8981\u6620\u5c04\u5927\u91cf\u6574\u6570\u5230boolean\u6807\u8bb0\u65f6\u4e0d\u8981\u5fd8\u8bb0 bit sets\u3002<\/li>\n<li>\u6574\u6570\u503c\u7684\u96c6\u5408\u5e94\u8be5\u7528 bit sets \u66ff\u4ee3\uff0c\u5728\u5927\u591a\u6570\u60c5\u51b5\u4e0b\u53ef\u4ee5\u8282\u7701\u5f88\u591a\u5185\u5b58\u3002<\/li>\n<\/ul>\n<h3><a href=\"http:\/\/java-performance.info\/java-util-identityhashmap\/\">IdentityHashMap<\/a><\/h3>\n<ul>\n<li><code>IdentityHashMap<\/code> \u4f7f\u7528 <code>System.identityHashCode<\/code> \u65b9\u6cd5\u6765\u83b7\u53d6\u5bf9\u8c61\u7684\u6807\u8bc6\u54c8\u5e0c\u7801\u3002\u5982\u679c\u4f60\u7684\u5bf9\u8c61\u6709\u4e3b\u952e\u5b57\u6bb5\u5219\u907f\u514d\u4f7f\u7528 <code>IdentityHashMap<\/code>\u3002<\/li>\n<li>\u4e0d\u8981\u5c1d\u8bd5\u53bb\u8fed\u4ee3 <code>IdentityHashMap<\/code> \u91cc\u7684\u5185\u5bb9\uff0c\u56e0\u4e3a\u8fed\u4ee3\u987a\u5e8f\u5728\u4f60\u7684\u7a0b\u5e8f\u7684\u6bcf\u6b21\u8fd0\u884c\u90fd\u662f\u4e0d\u540c\u7684\uff0c\u56e0\u800c\u5bfc\u81f4\u4f60\u7684\u7a0b\u5e8f\u7ed3\u679c\u4e0d\u4e00\u81f4\u3002<\/li>\n<li>\u8bbf\u95ee\u5bf9\u8c61\u7684\u6807\u8bc6\u54c8\u5e0c\u7801\u662f\u975e\u5e38\u4fbf\u5b9c\u7684 Java \u5185\u90e8\u64cd\u4f5c\u3002<\/li>\n<li>\u6ce8\u610f\uff0c\u5df2\u8ba1\u7b97\u4e86\u6807\u8bc6\u54c8\u5e0c\u7801\u7684\u5bf9\u8c61\u4e0d\u80fd\u7528\u4e8e<a href=\"https:\/\/wikis.oracle.com\/display\/HotSpotInternals\/Synchronization\">\u504f\u5411\u9501<\/a>\u3002<\/li>\n<\/ul>\n<h3><a href=\"http:\/\/java-performance.info\/regexp-related-methods-of-string\/\">String \u91cc\u6b63\u5219\u6709\u5173\u7684\u65b9\u6cd5<\/a><\/h3>\n<ul>\n<li>\u603b\u662f\u4f7f\u7528 <code>Matcher<\/code> \u548c <code>Pattern<\/code> \u66ff\u6362 <code>String.matches, split, replaceAll, replaceFirst<\/code> \u65b9\u6cd5\u3002<\/li>\n<li>\u5728Java 7\u91cc\uff0c\u6309\u5355\u4e2a\u975e\u6b63\u5219\u7279\u6b8a\u5b57\u7b26\u7684\u5b57\u7b26\u4e32\u5206\u5272\u5b57\u7b26\u4e32\u5df2\u5728 <code>String.split<\/code> \u65b9\u6cd5\u91cc\u4f18\u5316\u4e86\u3002<\/li>\n<li>\u5728\u6240\u6709\u5176\u4ed6\u7b80\u5355\u60c5\u51b5\u4e0b\uff0c\u5728\u65f6\u95f4\u5173\u952e\u7684\u4ee3\u7801\u91cc\u5bf9\u7b80\u5355\u7684\u60c5\u51b5\u8003\u8651\u4eb2\u624b\u5199\u89e3\u6790\u65b9\u6cd5\u3002\u901a\u8fc7\u624b\u5de5\u5236\u4f5c\u7684\u65b9\u6cd5\u6765\u66ff\u6362 Pattern \u65b9\u6cd5\uff0c\u4f60\u53ef\u4ee5\u5f88\u5bb9\u6613\u83b7\u5f9710\u500d\u63d0\u901f\u3002<\/li>\n<\/ul>\n<h3><a href=\"http:\/\/java-performance.info\/java-util-date-java-util-calendar-and-java-text-simpledateformat\/\">java.util.Date, java.util.Calendar and java.text.SimpleDateFormat \u6027\u80fd<\/a><\/h3>\n<ul>\n<li>\u4e0d\u8981\u4f7f\u7528 <code>java.util.Date<\/code>\uff0c\u9664\u975e\u5fc5\u987b\u3002\u7528\u4e00\u4e2a\u666e\u901a\u7684 long \u6765\u66ff\u4ee3\u3002<\/li>\n<li><code>java.util.Calendar<\/code> \u5bf9\u4e8e\u65e5\u671f\u8ba1\u7b97\u548c\u56fd\u9645\u5316\u5f88\u6709\u7528\uff0c\u4f46\u907f\u514d\u5927\u91cf\u5b58\u50a8\u8fd9\u4e9b\u5bf9\u8c61\u6216\u5e7f\u6cdb\u5730\u521b\u5efa\u5b83\u4eec\uff0c\u5b83\u4eec\u6d88\u8017\u5927\u91cf\u5185\u5b58\u5e76\u4e14\u521b\u5efa\u7684\u5f00\u9500\u5f88\u5927\u3002<\/li>\n<li><code>java.text.SimpleDateFormat<\/code> \u5bf9\u4e8e\u4e00\u822c\u60c5\u51b5\u4e0b\u7684\u65e5\u671f\u65f6\u95f4\u89e3\u6790\u5f88\u6709\u7528\uff0c\u4f46\u6700\u597d\u907f\u514d\u7528\u5b83\uff0c\u5982\u679c\u4f60\u9700\u8981\u4ee5\u540c\u6837\u7684\u683c\u5f0f\u89e3\u6790\u5927\u91cf\u7684date\u3002\u624b\u5de5\u5b9e\u73b0\u4e00\u4e2a\u89e3\u6790\u5668\u66f4\u597d\u3002<\/li>\n<\/ul>\n<h3><a href=\"http:\/\/java-performance.info\/joda-time-performance\/\">Joda \u65f6\u95f4\u5e93\u7684\u6027\u80fd<\/a><\/h3>\n<p>Java 8 \u91cc\u7684\u65e5\u671f\u65f6\u95f4\u5e93\u5c31\u662f\u57fa\u4e8e Joda \u65f6\u95f4\u5e93\u7684\u3002<\/p>\n<ul>\n<li>\u6240\u6709 Joda \u65f6\u95f4 <code>date\/time<\/code> \u5bf9\u8c61\u90fd\u662f\u6784\u5efa\u5728 long \u65f6\u95f4\u6233\u4e4b\u4e0a\uff0c\u6240\u4ee5\u4ece long \u6784\u5efa\u8fd9\u4e9b\u5bf9\u8c61\u5f88\u4fbf\u5b9c\u3002<\/li>\n<li>Joda \u4e0d\u5728\u5185\u90e8\u4fdd\u5b58\u4eba\u7c7b\u65f6\u95f4 &#8211; <code>year\/month\/day\/hour\/min\/second<\/code>\u3002\u8fd9\u610f\u5473\u7740\u5728Joda\u5bf9\u8c61\u4e0a\u83b7\u53d6\u4eba\u7c7b\u65f6\u95f4\u66f4\u6602\u8d35\uff0c\u5982\u679c\u4f60\u9700\u8981\u83b7\u53d6\u591a\u4e2a\u5b57\u6bb5\u3002<\/li>\n<li>Joda\u91cc <code>date\/time<\/code> \u7684\u89e3\u6790\u6bd4 JDK <code>SimpleDateFormat<\/code> \u7565\u5fae\u5feb\u3002Joda \u89e3\u6790\u7684\u4f18\u52bf\u662f\u6784\u5efa\u4e00\u4e2a\u89e3\u6790\u5668 &#8212; DateTimeFormatter &#8212; \u975e\u5e38\u4fbf\u5b9c\uff0c\u4e0d\u50cf\u6602\u8d35\u7684 <code>SimpleDateFormat<\/code>\uff0c\u6240\u4ee5\u4f60\u4e0d\u9700\u8981\u7f13\u5b58\u89e3\u6790\u5668\u3002<\/li>\n<\/ul>\n<h3><a href=\"http:\/\/java-performance.info\/jsr-310-java-8-datetime-library-performance-well-joda-time-2-3-j-u-calendar\/\">JSR 310 &#8211; Java 8 Date\/Time library performance (as well as Joda Time 2.3 and j.u.Calendar)<\/a><\/h3>\n<ul>\n<li>Java 8 \u91cc\u7684 <code>date\/time<\/code> \u662f\u6784\u5efa\u5728\u4eba\u7c7b\u65f6\u95f4\u4e4b\u4e0a\u7684 &#8212; <code>year\/month\/day\/hour\/minute\/second\/nanos<\/code>\u3002<\/li>\n<\/ul>\n<h3><a href=\"http:\/\/java-performance.info\/java-io-bytearrayoutputstream\/\">java.io.ByteArrayOutputStream<\/a><\/h3>\n<p>\u4e0d\u8981\u5728\u6027\u80fd\u5173\u952e\u4ee3\u7801\u91cc\u4f7f\u7528 ByteArrayOutputStream \u3002<\/p>\n<p>ByteArrayOutputStream \u4e3b\u8981\u7528\u4e8e\u5199\u672a\u77e5\u957f\u5ea6\u7684\u6d88\u606f\u5230\u8f93\u51fa\u6d41\u7684\u60c5\u51b5\u3002\u5b83\u662f\u57fa\u4e8e\u5b57\u8282\u6570\u7ec4\u5b9e\u73b0\u7684\uff0c\u5f53\u5e95\u5c42\u6570\u7ec4\u4e0d\u591f\u65f6\u5c31\u65b0\u5efa\u4e00\u4e2a\u66f4\u5927\u7684\uff0c\u628a\u539f\u6709\u6570\u636e\u62f7\u8d1d\u5230\u65b0\u6570\u7ec4\uff0c\u518d\u7528\u65b0\u6570\u7ec4\u66ff\u4ee3\u539f\u6709\u6570\u7ec4\uff1b\u6240\u6709\u65b9\u6cd5\u90fd\u662f\u540c\u6b65\u7684\u3002<\/p>\n<ul>\n<li>\u5728\u6027\u80fd\u5173\u952e\u4ee3\u7801\uff0c\u5c1d\u8bd5\u7528 ByteBuffer \u66ff\u4ee3 ByteArrayOutputStream\uff0c\u5982\u679c\u4e00\u5b9a\u8981\u7528\uff0c\u53bb\u9664\u5b83\u7684\u540c\u6b65\u3002<\/li>\n<li>\u5982\u679c\u4f60\u7684\u65b9\u6cd5\u5199\u4e00\u4e9b\u6d88\u606f\u5230\u672a\u77e5\u7684 OutputStream\uff0c\u603b\u662f\u5148\u5199\u6d88\u606f\u5230 ByteArrayOutputStream \uff0c\u7136\u540e\u4f7f\u7528\u5b83\u7684 <code>writeTo(OutputStream)<\/code> \u65b9\u6cd5\u3002\u5728\u4e00\u4e9b\u7a00\u6709\u7684\u60c5\u51b5\u4e0b\u4ece\u5b57\u8282\u8868\u793a\u91cc\u6784\u5efa\u5b57\u7b26\u4e32\uff0c\u53ef\u4ee5\u4f7f\u7528 <code>ByteArrayOutputStream.toString<\/code> \u65b9\u6cd5\u3002<\/li>\n<li>\n<p>\u901a\u5e38\u60c5\u51b5\u4e0b\u907f\u514d <code>ByteArrayOutputStream.toByteArray<\/code> \u65b9\u6cd5\uff0c\u5b83\u521b\u5efa\u4e00\u4e2a\u5185\u90e8\u5b57\u8282\u6570\u7ec4\u7684\u62f7\u8d1d\u3002\u5982\u679c\u4f60\u7684\u5e94\u7528\u7a0b\u5e8f\u4f7f\u7528\u4e86GB\u5185\u5b58\uff0cGC\u8fd9\u4e9b\u62f7\u8d1d\u7684\u65f6\u95f4\u662f\u663e\u8457\u7684\u3002<\/p>\n<\/li>\n<li>\n<p>\u5982\u679c\u4f60\u9884\u5148\u77e5\u9053\u4f60\u7684\u6d88\u606f\u5927\u5c0f\uff08\u6216\u81f3\u5c11\u77e5\u9053\u5b83\u7684\u4e0a\u9650\uff09\uff0c\u7528 ByteBuffer \u66ff\u4ee3\uff08\u6216\u91cd\u7528\u4e4b\u524d\u5206\u914d\u7684\uff09\uff0c\u518d\u5199\u6d88\u606f\u5230\u5b83\u3002<\/p>\n<\/li>\n<li>\u5982\u679c\u662f\u51fa\u4e8e\u7f13\u5b58\u7684\u8003\u8651\uff0c\u53ef\u4ee5\u4f7f\u7528 <code>BufferedOutputStream<\/code> \u6765\u66ff\u4ee3\u3002<\/li>\n<li><code>ByteArrayOutputStream.writeTo(OutputStream)<\/code> \u65b9\u6cd5\u4f7f\u7528\u5185\u90e8\u6570\u7ec4\u800c\u4e0d\u662f\u521b\u5efa\u62f7\u8d1d\u3002<\/li>\n<li><code>ByteArrayOutputStream.toString(String charsetName)<\/code>  \u548c <code>ByteArrayOutputStream.toString(String charsetName)<\/code> \u5141\u8bb8\u76f4\u63a5\u4ece\u5185\u90e8\u6570\u7ec4\u521b\u5efa\u4e00\u4e2a\u5b57\u7b26\u4e32\u3002<\/li>\n<\/ul>\n<h3><a href=\"http:\/\/java-performance.info\/java-io-bufferedinputstream-and-java-util-zip-gzipinputstream\/\">BufferedInputStream \u548c GZIPInputStream<\/a><\/h3>\n<ul>\n<li>BufferedInputStream \u548c GZIPInputStream \u90fd\u6709\u5185\u90e8\u7684\u7f13\u5b58\u3002\u9ed8\u8ba4\u5927\u5c0f\uff1a\u524d\u8005\u662f 8192 \u5b57\u8282\uff0c\u540e\u8005\u662f 512 \u5b57\u8282\u3002\u901a\u5e38\u60c5\u51b5\u4e0b\u5b83\u4eec\u53ef\u4ee5\u589e\u957f\u5230\u6700\u591a 65536\u3002<\/li>\n<li>\u4e0d\u8981\u7528 BufferedInputStream \u4f5c\u4e3a GZIPInputStream \u7684\u8f93\u5165\uff0c\u800c\u662f\u5728\u6784\u9020\u5668\u91cc\u663e\u5f0f\u8bbe\u7f6e GZIPInputStream \u7684\u7f13\u5b58\u5927\u5c0f\u3002\u867d\u7136\uff0c\u4fdd\u7559\u4e00\u4e2a BufferedInputStream  \u4ecd\u7136\u662f\u5b89\u5168\u7684\u3002<\/li>\n<li>\u5982\u679c\u4f60\u6709\u4e00\u4e2a\u65b0\u7684 <code>BufferedInputStream( new FileInputStream( file ) )<\/code> \u5bf9\u8c61\uff0c\u4f60\u53ef\u4ee5\u66f4\u9891\u7e41\u5730\u8c03\u7528\u5b83\u7684\u53ef\u7528\u65b9\u6cd5\uff0c\u8003\u8651\u91cd\u5199 BufferedInputStream \u7684\u53ef\u8bbf\u95ee\u65b9\u6cd5\uff0c\u5c06\u6781\u5927\u63d0\u5347\u6587\u4ef6\u8bfb\u53d6\u901f\u5ea6\u3002<\/li>\n<\/ul>\n<h3><a href=\"http:\/\/java-performance.info\/java-lang-byte-short-integer-long-character-boxing-and-unboxing\/\">Byte\u3001Short\u3001Integer\u3001Long\u3001Character\uff08\u88c5\u7bb1\u548c\u62c6\u7bb1\uff09<\/a><\/h3>\n<ul>\n<li>\u7edd\u4e0d\u4f7f\u7528 <code>Number<\/code> \u5b50\u7c7b\u7684 <code>valueOf(String)<\/code> \u65b9\u6cd5\u3002\u5982\u679c\u9700\u8981\u4e00\u4e2a\u539f\u59cb\u7c7b\u578b\u7684\u503c\uff0c\u7528 <code>parse[Type]<\/code> \u3002\u5982\u679c\u9700\u8981\u4e00\u4e2a\u5305\u88c5\u7c7b\u7684\u5b9e\u4f8b\uff0c\u4ecd\u7136\u8c03\u7528 <code>parse[Type]<\/code> \u5e76\u4f9d\u8d56\u4e8e JVM \u5b9e\u73b0\u7684\u88c5\u7bb1\u3002\u5b83\u5c06\u652f\u6301\u7f13\u5b58\u6700\u5e38\u4f7f\u7528\u7684\u503c\u3002\u7edd\u4e0d\u8981\u4f7f\u7528\u5305\u88c5\u7c7b\u7684\u6784\u9020\u5668\uff0c\u5b83\u4eec\u603b\u662f\u8fd4\u56de\u4e00\u4e2a\u65b0\u5bf9\u8c61\uff0c\u56e0\u4e3a\u7ed5\u8fc7\u4e86\u7f13\u5b58\u3002\u4e0b\u9762\u662f\u652f\u6301\u7f13\u5b58\u7684\u4e0d\u540c\u7c7b\u578b\u7684\u8303\u56f4\uff1a<\/li>\n<\/ul>\n<table>\n<tr>\n<td>Byte, Short, Long<\/td>\n<td>Character<\/td>\n<td>Integer<\/td>\n<td>Float, Double<\/td>\n<\/tr>\n<tr>\n<td>-128 \u81f3 127<\/td>\n<td>0 \u81f3 127<\/td>\n<td>-128 \u81f3 Integer.IntegerCache.high \u6216 127<\/td>\n<td>\u4e0d\u7f13\u5b58<\/td>\n<\/tr>\n<\/table>\n<h3><a href=\"http:\/\/java-performance.info\/map-containskeyset-contains\/\">Map.containsKey\/Set.contains<\/a><\/h3>\n<ul>\n<li>\u5bf9\u4e8e sets\uff0c<code>contains<\/code> + <code>add\/remove<\/code> \u8c03\u7528\u5bf9\u5e94\u8be5\u7528\u5355\u4e2a <code>add\/remove<\/code> \u8c03\u7528\u66ff\u4ee3\uff0c\u5373\u4f7f\u6709\u989d\u5916\u903b\u8f91\u7528\u4e8e\u4fdd\u8bc1 <code>contains<\/code> \u8c03\u7528\u3002<\/li>\n<li>\u5bf9\u4e8e maps\uff0c <code>contains<\/code> + <code>get<\/code> \u8c03\u7528\u7ec4\u5408\u5e94\u8be5\u603b\u662f\u7528 <code>get<\/code> \u540e\u63a5\u5bf9 <code>get<\/code> \u7ed3\u679c\u7684\u975e\u7a7a\u68c0\u6d4b\u66ff\u4ee3\u3002\uff08\u8fd9\u4e24\u4e2a\u6280\u5de7\u90fd\u662f\u51cf\u5c11\u4e86\u4e00\u6b21\u67e5\u627e\uff09<\/li>\n<li>\u5bf9\u4e8e maps \u952e\u503c\u5bf9\u7684\u904d\u5386\uff0c\u5e94\u8be5\u901a\u8fc7 <code>Map.entrySet<\/code> \u65b9\u6cd5\u7684\u7ed3\u679c\u8fdb\u884c\u904d\u5386\uff0c\u800c\u4e0d\u662f\u901a\u8fc7 <code>Map.keySet<\/code> \u548c <code>Map.get(key)<\/code> \u7684\u7ec4\u5408\u8fdb\u884c\u3002<\/li>\n<\/ul>\n<h3><a href=\"http:\/\/java-performance.info\/java-crc32-and-adler32\/\">java.util.zip.CRC32 and java.util.zip.Adler32 performance<\/a><\/h3>\n<ul>\n<li>\u5982\u679c\u4f60\u9009\u62e9\u4f7f\u7528\u54ea\u4e2achecksum\uff0c\u9996\u5148\u5c1d\u8bd5 <code>Adler32<\/code>\u3002\u5982\u679c\u5b83\u7684\u8d28\u91cf\u5bf9\u4f60\u8db3\u591f\uff0c\u7528\u5b83\u800c\u4e0d\u662f <code>CRC32<\/code>\u3002\u4efb\u4f55\u60c5\u51b5\u4e0b\uff0c\u7528 <code>Checksum<\/code> \u63a5\u53e3\u6765\u83b7\u53d6 <code>Adler32\/CRC32<\/code> \u7684\u903b\u8f91\u3002<\/li>\n<li>\u5c1d\u8bd5\u66f4\u65b0 checksum \u81f3\u5c11\u8981\u6709 500 \u5b57\u8282\u5757\u3002\u66f4\u77ed\u7684\u5757\u5c06\u8981\u6c42\u663e\u8457\u7684\u65f6\u95f4\u5f00\u9500\u7528\u4e8e JNI \u8c03\u7528\u3002<\/li>\n<\/ul>\n<h3><a href=\"http:\/\/java-performance.info\/hashcode-method-performance-tuning\/\">hashCode \u65b9\u6cd5\u6027\u80fd\u8c03\u4f18<\/a><\/h3>\n<ul>\n<li>\u5c1d\u8bd5\u63d0\u9ad8 hashCode \u65b9\u6cd5\u7684\u7ed3\u679c\u7684\u5206\u5e03\u6027\u3002\u8fd9\u8fdc\u6bd4\u63d0\u9ad8\u6b64\u65b9\u6cd5\u7684\u901f\u5ea6\u66f4\u91cd\u8981\u3002\u7edd\u4e0d\u8981\u5199\u4e00\u4e2a\u8fd4\u56de\u5e38\u91cf\u7684 hashCode \u65b9\u6cd5\u3002<\/li>\n<li><code>String.hashCode<\/code> \u7ed3\u679c\u7684\u5206\u5e03\u6027\u51e0\u4e4e\u5b8c\u7f8e\uff0c\u6240\u4ee5\u6709\u65f6\u4f60\u53ef\u4ee5\u7528String\u7684\u54c8\u5e0c\u7801\u6765\u66ff\u4ee3\u5b83\u4eec\u3002\u5982\u679c\u4f60\u4e0e\u5b57\u7b26\u4e32\u96c6\u5408\u4e00\u8d77\u5de5\u4f5c\uff0c\u5c1d\u8bd5\u7528 <code>BitSet<\/code> \u6765\u7ed3\u675f\u3002\uff08\u610f\u601d\u662f<code>BitSet<\/code>+\u54c8\u5e0c\u7801\u53ef\u4ee5\u5b8c\u7f8e\u66ff\u4ee3\u5b57\u7b26\u4e32\u96c6\u5408\uff0c\u5e76\u63d0\u5347\u6027\u80fd\u3002\uff09<\/li>\n<\/ul>\n<h3><a href=\"http:\/\/java-performance.info\/throwing-an-exception-in-java-is-very-slow\/\">\u5728Java\u91cc\u629b\u51fa\u5f02\u5e38\u662f\u5f88\u6162\u7684<\/a><\/h3>\n<ul>\n<li>\u7edd\u4e0d\u7528\u5f02\u5e38\u4f5c\u4e3a\u8fd4\u56de\u7801\u7684\u66ff\u4ee3 \u6216 \u4efb\u4f55\u53ef\u80fd\u53d1\u751f\u7684\u4e8b\u4ef6\u3002\u629b\u51fa\u5f02\u5e38\u662f\u5f88\u6602\u8d35\u7684 &#8212; \u5bf9\u4e8e\u7b80\u5355\u7684\u65b9\u6cd5\u4f60\u5c06\u7ecf\u5386100\u500d\u51cf\u901f\u3002<\/li>\n<li>\u907f\u514d\u4f7f\u7528\u4efb\u4f55 <code>Number<\/code> \u5b50\u7c7b\u7684 <code>parse*\/valueOf<\/code>\uff08\u8fd9\u4e9b\u65b9\u6cd5\u4f1a\u629b\u51fa <code>NumberFormatException<\/code>\uff09\uff0c\u5982\u679c\u4f60\u5bf9\u4f60\u7684\u6bcf\u4e2a\u6570\u636e\u7247\u6bb5\u8c03\u7528\u5b83\u4eec\u5e76\u4e14\u4f60\u9884\u671f\u6709\u5f88\u591a\u975e\u6570\u5b57\u7684\u6570\u636e\u3002\u4e3a\u66f4\u9ad8\u6027\u80fd\uff0c\u624b\u52a8\u89e3\u6790\u8fd9\u4e9b\u503c\u3002<\/li>\n<\/ul>\n<h3><a href=\"http:\/\/java-performance.info\/java-logging-performance\/\">Java \u65e5\u5fd7\u6027\u80fd\u9677\u9631<\/a><\/h3>\n<p>\u5982\u4f55\u7528\u6700\u65b0\u7684\u6027\u80fd\u635f\u5931\u5199\u65e5\u5fd7\u6d88\u606f\uff1a<\/p>\n<ul>\n<li>\u5982\u679c\u4f60\u5728\u4e3a\u65e5\u5fd7\u6d88\u606f\u51c6\u5907\u6570\u636e\u65f6\u9700\u8981\u505a\u6602\u8d35\u7684\u8ba1\u7b97\uff0c\u8981\u4e48\u4f7f\u7528 <code>Logger.isLoggable<\/code> \u5e76\u5728\u91cc\u9762\u505a\u6240\u6709\u7684\u6570\u636e\u51c6\u5907\uff0c\u8981\u4e48\u5199\u4e00\u4e2a\u5bf9\u8c61 &#8212; \u5b83\u7684 <code>toString<\/code> \u5b8c\u6210\u6240\u6709\u7684\u8ba1\u7b97\u3002<\/li>\n<li>\u7edd\u4e0d\u8c03\u7528 <code>Object.toString<\/code> \u65b9\u6cd5\u6765\u83b7\u53d6\u4e00\u4e2a\u65e5\u5fd7\u6d88\u606f\u53c2\u6570 &#8212; \u4ec5\u4ec5\u4f20\u9012\u539f\u59cb\u5bf9\u8c61\u3002\u65e5\u5fd7\u6846\u67b6\u4f1a\u8c03\u7528\u4f60\u7684\u5bf9\u8c61\u7684 <code>toString<\/code> \u65b9\u6cd5\u3002\uff08\u6ce8\uff1a\u8fd9\u662f\u4e00\u4e2a\u5ef6\u8fdf\u8ba1\u7b97\u7684\u95ee\u9898\uff0c\u65e5\u5fd7\u6846\u67b6\u53ea\u4f1a\u5728\u9700\u8981\u7684\u65f6\u5019\u8c03\u7528\uff0c\u4e5f\u5c31\u662f\u5728\u771f\u6b63\u9700\u8981\u65f6\u624d\u8ba1\u7b97\uff1b\u800c\u4ee3\u7801\u76f4\u63a5\u8c03\u7528\u5219\u4f1a\u5728\u8c03\u7528\u65e5\u5fd7\u6846\u67b6\u7684\u65b9\u6cd5\u65f6\u5b8c\u6210\u8ba1\u7b97\u3002\uff09<\/li>\n<li>\u4e0d\u8981\u6df7\u6dc6\u65e5\u5fd7\u53c2\u6570\u7684\u5b57\u7b26\u4e32\u4e32\u8054 &#8212; \u6076\u610f\u4e32\u8054\u7684\u5b57\u7b26\u4e32\u5c06\u5141\u8bb8\u4f60\u7684\u5e94\u7528\u7a0b\u5e8f\u7528\u6237\u7a81\u7834\u4f60\u7684 logging\/access \u6570\u636e\uff0c\u90a3\u662f\u5047\u5b9a\u4e0d\u7528\u4e8e\u7528\u6237\u8bbf\u95ee\u7684\u3002<\/li>\n<\/ul>\n<h3><a href=\"http:\/\/java-performance.info\/base64-encoding-and-decoding-performance\/\">Base64 \u7f16\u7801\u548c\u89e3\u7801\u6027\u80fd<\/a><\/h3>\n<ul>\n<li>\u5982\u679c\u4f60\u5728\u627e\u4e00\u4e2a\u5feb\u901f\u53ef\u9760\u7684 Base64 \u7f16\u89e3\u7801\u5668 &#8212; \u975eJDK\u4ee5\u5916\u3002\u5728Java8\u91cc\u6709\u4e00\u4e2a\u65b0\u7684\u7f16\u89e3\u7801\u5668\uff1a <code>java.util.Base64<\/code>\uff0c\u4e5f\u6709\u4e00\u4e2a\u9690\u85cf\u7684\uff1a <code>javax.xml.bind.DatatypeConverter<\/code>\u3002\u90fd\u662f\u5feb\u901f\u3001\u53ef\u9760\u4e14\u4e0d\u4f1a\u906d\u53d7\u6b63\u6570\u6ea2\u51fa\u3002<\/li>\n<li>\u6709\u4e9b\u7b2c\u4e09\u65b9\u5f00\u6e90\u7684Base64\u7f16\u89e3\u7801\u5668\u5728\u80fd\u5904\u7406\u7684\u6570\u636e\u7684\u5927\u5c0f\u4e0a\u662f\u6709\u9650\u5236\u7684\u3002<\/li>\n<li>\u4e0d\u8981\u5728\u5de8\u5927\u7684\u5b57\u7b26\u4e32\u4e0a\u8c03\u7528 <code>String.getBytes(Charset)<\/code>\uff0c\u5982\u679c\u4f60\u7684\u5b57\u7b26\u96c6\u662f\u591a\u5b57\u8282\u7684 &#8212; \u4f60\u53ef\u80fd\u5f97\u5230\u6b63\u6570\u6ea2\u51fa\u6709\u5173\u7684\u5f02\u5e38\u3002<\/li>\n<\/ul>\n<h3><a href=\"http:\/\/java-performance.info\/java-util-random-java-util-concurrent-threadlocalrandom-multithreaded-environments\/\">\u591a\u7ebf\u7a0b\u73af\u5883\u4e0b\u7684 java.util.Random \u548c java.util.concurrent.ThreadLocalRandom<\/a><\/h3>\n<ul>\n<li>\u5728\u4efb\u4f55\u60c5\u5883\u4e0b\u90fd\u4e0d\u8981\u5728\u591a\u4e2a\u7ebf\u7a0b\u95f4\u4f7f\u7528 java.util.Random \uff0c\u628a\u5b83\u5305\u88c5\u5728 ThreadLocal \u91cc\u3002<\/li>\n<li>\u4ece Java 7 \u5f00\u59cb\uff0c\u5728\u6240\u6709\u60c5\u5883\u4e0b\u9996\u9009 java.util.concurrent.ThreadLocalRandom \u800c\u4e0d\u662f java.util.Random &#8212; \u5b83\u662f\u5411\u540e\u517c\u5bb9\u5df2\u6709\u4ee3\u7801\u7684\uff0c\u4f46\u5185\u90e8\u4f7f\u7528\u66f4\u5c11\u7684\u64cd\u4f5c\u3002<\/li>\n<\/ul>\n<h3><a href=\"http:\/\/java-performance.info\/charset-encoding-decoding-java-78\/\">Java 7\/8 \u91cc\u7684\u5b57\u7b26\u4e32\u7f16\u7801\u548c\u89e3\u7801<\/a><\/h3>\n<ul>\n<li>\u603b\u662f\u503e\u5411\u4e8e\u56fd\u5bb6\u5b57\u7b26\u96c6\u5982  windows-1252 \u6216 Shift_JIS \u800c\u4e0d\u662f UTF-8\uff1a\u5b83\u4eec\u751f\u6210\u66f4\u7d27\u51d1\u7684\u4e8c\u8fdb\u5236\u8868\u793a\uff08\u4f5c\u4e3a\u4e00\u4e2a\u89c4\u5219\uff09\u5e76\u4e14\u5b83\u4eec\u7f16\u7801\/\u89e3\u7801\u66f4\u5feb\u3002<\/li>\n<li>\u5728Java 7 \u548c 8 \u91cc ISO-8869-1 \u603b\u662f\u6bd4 US-ASCII\u5de5\u4f5c\u5f97\u66f4\u5feb\u3002<\/li>\n<li>\u5bf9\u4e8e  US-ASCII\/ISO-8859-1\uff0c\u4f60\u53ef\u4ee5\u5199\u4e00\u4e2a\u5feb\u901f\u7684 <code>String-&gt;byte[]<\/code> \u8f6c\u6362\uff0c\u4f46\u4f60\u4e0d\u80fd\u6253\u8d25 Java \u89e3\u7801\u5668\uff0c\u5b83\u4eec\u76f4\u63a5\u8bbf\u95ee\u5b83\u4eec\u521b\u5efa\u7684\u5b57\u7b26\u4e32\u8f93\u51fa\u3002<\/li>\n<\/ul>\n<h2>\u4e8c\u3001\u5185\u5b58\u4f18\u5316<\/h2>\n<h3><a href=\"http:\/\/java-performance.info\/overview-of-memory-saving-techniques-java\/\">Java \u91cc\u5185\u5b58\u8282\u7ea6\u6280\u672f\u6982\u8981<\/a><\/h3>\n<p>\u8fd9\u7bc7\u6587\u7ae0\u5c06\u7ed9\u4f60java\u91cc\u5185\u5b58\u4f18\u5316\u7684\u57fa\u672c\u5efa\u8bae\u3002\u5927\u591a\u6570Java\u5185\u5b58\u4f18\u5316\u6280\u672f\u90fd\u662f\u57fa\u4e8e\u8fd9\u4e9b\u5efa\u8bae\u7684\u3002<\/p>\n<ul>\n<li>\u9996\u9009\u57fa\u672c\u7c7b\u578b\u800c\u4e0d\u662f\u5b83\u4eec\u7684\u5305\u88c5\u5bf9\u8c61\u3002<\/li>\n<li>\u5c1d\u8bd5\u51cf\u5c11\u4f60\u7684\u5bf9\u8c61\u6570\u91cf\u3002\u4f8b\u5982\uff0c\u9996\u9009\u57fa\u4e8e\u6570\u7ec4\u7684\u7ed3\u6784\uff08\u5982 <code>ArrayList\/ArrayDeque<\/code>\uff09\u800c\u4e0d\u662f\u57fa\u4e8e\u6307\u9488\u7684\u7ed3\u6784\uff08\u5982 <code>LinkedList<\/code>)\u3002<\/li>\n<\/ul>\n<h3><a href=\"http:\/\/java-performance.info\/memory-consumption-of-java-data-types-1\/\">\u6d41\u884cJava\u6570\u636e\u7c7b\u578b\u7684\u5185\u5b58\u6d88\u8017<\/a><\/h3>\n<table>\n<tr>\n<td>EnumSet, BitSet<\/td>\n<td>1 bit per value<\/td>\n<\/tr>\n<tr>\n<td>EnumMap<\/td>\n<td>4 bytes (for value, nothing for key)<\/td>\n<\/tr>\n<tr>\n<td>ArrayList<\/td>\n<td>4 bytes (but may be more if ArrayList capacity is seriously more than its size)<\/td>\n<\/tr>\n<tr>\n<td>LinkedList<\/td>\n<td>24 bytes (fixed)<\/td>\n<\/tr>\n<tr>\n<td>ArrayDeque<\/td>\n<td>4 to 8 bytes, 6 bytes on average<\/td>\n<\/tr>\n<\/table>\n<h3><a href=\"http:\/\/java-performance.info\/a-few-more-memory-saving-techniques-in-java\/\">Java \u91cc\u7684\u5185\u5b58\u8282\u7ea6\u6280\u672f<\/a><\/h3>\n<p>\u8fd9\u7bc7\u6587\u7ae0\u63cf\u8ff0\u4e86\u9759\u6001\u5185\u90e8\u7c7b\u3001\u5b57\u7b26\u4e32\u6c60\u3001\u5e03\u5c14\u6807\u8bb0\u96c6\u5408\u548cJDK\u91cc\u4e00\u4e9b\u7279\u6b8a\u7c7b\u7684\u5fae\u5c0f\u96c6\u5408\u7684\u597d\u5904\u3002<\/p>\n<ul>\n<li>\u9ed8\u8ba4\u8ba9\u6240\u6709\u5185\u90e8\u7c7b\u662f\u9759\u6001\u7684\u3002\u53ea\u6709\u5fc5\u987b\u65f6\u624d\u79fb\u9664 <code>static<\/code> \u4fee\u9970\u7b26\u3002<\/li>\n<li>\u5982\u679c\u4f60\u6709\u901a\u5e38\u662f\u5c0f\u96c6\u5408\u7684\u96c6\u5408\uff0c\u5c1d\u8bd5\u7528 <code>java.util.Collections.empty*\/singleton*<\/code> \u65b9\u6cd5\u8fbe\u5230\u5185\u5b58\u9ad8\u6548\u7684\u5b58\u50a8\u5fae\u5c0f\u96c6\u5408\u3002<\/li>\n<li>\u9996\u9009 <code>BitSet<\/code> \u800c\u4e0d\u662f boolean \u7684\u6570\u7ec4\u6216\u5217\u8868\u3001\u6216\u6574\u6570\u7c7b\u578b\u7684\u7a00\u758f\u96c6\u5408\uff1a\u4f4d\u96c6\u5408\u662f \u5185\u5b58\u548cCPU\u53cb\u597d\u7684\u3002<\/li>\n<\/ul>\n<h3><a href=\"http:\/\/java-performance.info\/string-intern-in-java-6-7-8\/\">Java 6,7,8 \u91cc\u7684 String.intern &#8211; \u5b57\u7b26\u4e32\u6c60<\/a><\/h3>\n<p>\u8fd9\u7bc7\u6587\u7ae0\u63cf\u8ff0\u4e86 Java 6 \u91cc <code>String.intern()<\/code> \u662f\u5982\u4f55\u5b9e\u73b0\u7684\uff0c Java 7 \u548c 8 \u91cc\u505a\u4e86\u4ec0\u4e48\u4fee\u6539\u3002<\/p>\n<ul>\n<li>\u5728Java 6\u91cc\u8fdc\u79bb <code>String.intern()<\/code> \u65b9\u6cd5\uff0c\u7531\u4e8e\u7528\u4e8eJVM\u5b57\u7b26\u4e32\u6c60\u5b58\u50a8\u7684\u56fa\u5b9a\u5927\u5c0f\u5185\u5b58\u533a\u57df\uff08PermGen\uff09\u3002<\/li>\n<li>Java 7 \u548c 8 \u5728\u5806\u5185\u5b58\u91cc\u5b9e\u73b0\u4e86\u5b57\u7b26\u4e32\u6c60\u3002\u8fd9\u610f\u5473\u7740\u5728 Java 7 \u548c 8 \u91cc\u5bf9\u4e8e\u5b57\u7b26\u4e32\u6c60\u4f60\u53d7\u9650\u4e8e\u6574\u4e2a\u5e94\u7528\u5185\u5b58\u3002<\/li>\n<li>\u5728 Java 7 \u548c 8 \u7528 JVM \u53c2\u6570 <code>-XX:StringTableSize<\/code> \u6765\u8bbe\u7f6e\u5b57\u7b26\u4e32\u5403\u7684map\u5927\u5c0f\u3002\u5b83\u662f\u56fa\u5b9a\u7684\uff0c\u56e0\u4e3a\u5b83\u88ab\u5b9e\u73b0\u4e3a\u5e26\u94fe\u8868\u4f4d\u6876\u7684 hash map\u3002\u4f30\u7b97\u4f60\u7684\u5e94\u7528\u91cc\u4e0d\u540c\u5b57\u7b26\u4e32\u662f\u6570\u91cf\uff0c\u8bbe\u7f6e\u6c60\u7684\u5927\u5c0f\u7b49\u4e8e\u63a5\u8fd1\u4e8e\u6c60\u5927\u5c0f\u7684 prime number\uff08\u7d20\u6570\uff09\u3002\u8fd9\u5c06\u8ba9 <code>String.intern<\/code> \u8fd0\u884c\u5728\u5e38\u91cf\u65f6\u95f4\uff0c\u5e76\u5bf9\u6bcf\u4e2ainterned\u7684\u5b57\u7b26\u4e32\u8981\u6c42\u66f4\u5c0f\u7684\u5185\u5b58\u5f00\u9500\u3002\uff08\u5bf9\u4e8e\u540c\u6837\u7684\u4efb\u52a1\uff0c\u663e\u5f0f\u4f7f\u7528 Java  <code>WeakHashMap<\/code> \u5c06\u591a\u6d88\u8017 4-5 \u500d\u7684\u5185\u5b58\uff09<\/li>\n<li><code>-XX:StringTableSize<\/code> \u7684\u9ed8\u8ba4\u503c\u5728 Java 7 \u91cc\u662f <code>1009<\/code>\uff0cJava 8 \u91cc\u662f <code>25-50K<\/code>\u3002<\/li>\n<\/ul>\n<h3><a href=\"http:\/\/java-performance.info\/string-intern-java-6-7-8-multithreaded-access\/\">Java 6,7,8 \u91cc\u7684 String.intern &#8211; \u591a\u7ebf\u7a0b\u8bbf\u95ee<\/a><\/h3>\n<p>\u8fd9\u7bc7\u6587\u7ae0\u63cf\u8ff0\u4e86\u591a\u7ebf\u7a0b\u8c03\u7528 <code>String.intern()<\/code> \u7684\u6027\u80fd\u5f71\u54cd\u3002<\/p>\n<ul>\n<li>\u968f\u610f\u5730\u4f7f\u7528 <code>String.intern()<\/code> \u3002<\/li>\n<li>JVM \u5b57\u7b26\u4e32\u6c60\u4e0d\u662f\u7ebf\u7a0b\u672c\u5730\u7684\u3002<\/li>\n<\/ul>\n<h3><a href=\"http:\/\/java-performance.info\/string-intern-java-7-8-part-3\/\">Java 6,7,8 \u91cc\u7684 String.intern &#8211; \u6700\u4f73\u5b9e\u8df5<\/a><\/h3>\n<ul>\n<li>\u867d\u7136 <code>Java 7+<\/code> \u5f00\u59cb <code>String.intern()<\/code> \u5b9e\u73b0\u6709\u4e86\u91cd\u5927\u4f18\u5316\uff0c\u5b83\u4ecd\u7136\u9700\u8981\u663e\u8457\u7684\u65f6\u95f4\u6765\u8fd0\u884c\uff08\u5bf9\u4e8eCPU\u654f\u611f\u7684\u5e94\u7528\u7a0b\u5e8f\u662f\u663e\u8457\u7684\uff09\u3002\u4f60\u4e0d\u5e94\u8be5\u7528 <code>String.intern()<\/code> \u4f5c\u4e3a\u5b89\u5168\u7f51\u7edc\uff0c\u628a\u4e00\u5207\u957f\u671f\u5b58\u6d3b\u5b57\u7b26\u4e32\u4e22\u7ed9\u5b83\u3002\u76f8\u53cd\uff0c\u5e94\u5f53\u53ea\u5904\u7406\u6709\u9650\u6570\u91cf\u7684\u4e0d\u91cd\u590d\u503c\u3002<\/li>\n<\/ul>\n<p><strong>\u6ce8\uff1a\u8fd8\u6709\u4e00\u4e9b\uff0c\u4f46\u611f\u89c9\u8ddfJava\u4ee3\u7801\u5173\u7cfb\u5c0f\uff0c\u4e0d\u7ffb\u8bd1\u4e86\u3002<\/strong><\/p>\n<h2>\u4e09\u3001\u5c0f\u6280\u5de7<\/h2>\n<h2>\u56db\u3001\u4f7f\u7528\u4e2a\u4f8b<\/h2>\n<hr\/>\n<p>\u6b22\u8fce\u5173\u6ce8\u6211\u7684\u5fae\u4fe1\u516c\u4f17\u53f7: <strong>coderbee\u7b14\u8bb0<\/strong>\uff0c\u53ef\u4ee5\u66f4\u53ca\u65f6\u56de\u590d\u4f60\u7684\u8ba8\u8bba\u3002<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" width=\"258\" height=\"258\" src=\"https:\/\/coderbee.net\/wp-content\/uploads\/2019\/01\/coderbee-note.jpg\" class=\"alignnone size-full wp-image-1707\"><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u672c\u6587\u4e3b\u8981\u57fa\u4e8e Java performance tuning tips or e &hellip; <a href=\"https:\/\/coderbee.net\/index.php\/java\/20140503\/907\">\u7ee7\u7eed\u9605\u8bfb <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[18],"tags":[231,165],"_links":{"self":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/907"}],"collection":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/comments?post=907"}],"version-history":[{"count":3,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/907\/revisions"}],"predecessor-version":[{"id":910,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/907\/revisions\/910"}],"wp:attachment":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/media?parent=907"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/categories?post=907"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/tags?post=907"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}