Java7的新特性

原文出处：xixicat

序

本文主要讲Java7的新特性，相对于Java6而言，Java7增加了一些重要的特性，比如NIO2，不像Java6那么鸡肋，也算是一个重要的版本。

特性列表

• suppress异常(新语法)

• 捕获多个异常(新语法)

• try-with-resources(新语法)

• JSR341-Expression Language Specification(新规范)

• JSR203-More New I/O APIs for the Java Platform(新规范)

• JSR292与InvokeDynamic

• 支持JDBC4.1规范

• Path接口、DirectoryStream、Files、WatchService

• jcmd

• fork/join framework

• Java Mission Control

1、suppress异常(新语法)

  1 /**
  2  * 记录异常，不被淹没
  3  * addSuppressed
  4  */
  5 class ReadFile {
  6     public void read(String filename) throws BaseException {
  7         FileInputStream input = null;
  8         IOException readException = null;
  9         try {
 10             input = new FileInputStream(filename);
 11         } catch (IOException ex) {
 12             readException = ex;
 13         } finally {
 14             if (input != null) {
 15                 try {
 16                     input.close();
 17                 } catch (IOException ex) {
 18                     if (readException == null) {
 19                         readException = ex;
 20                     }else{
 21                         //使用java7的
 22                         readException.addSuppressed(ex);
 23                     }
 24                 }
 25             }
 26             if (readException != null) {
 27                 throw new BaseException(readException);
 28             }
 29         }
 30     }
 31 }

2、捕获多个异常(新语法)

  1 public void handle() {
  2         ExceptionThrower thrower = new ExceptionThrower();
  3         try {
  4             thrower.manyExceptions();
  5         } catch (ExceptionA | ExceptionB ab) {
  6             System.out.println(ab.getClass());
  7         } catch (ExceptionC c) {
  8         }
  9     }

3、try-with-resources(新语法)

  1 /**
  2  * try-with-resource
  3  * 不需要使用finally来保证打开的流被正确关闭
  4  * 这是自动完成的。
  5  * @author patterncat
  6  * @created 2014-07-21
  7  */
  8 public class ResourceBasicUsage {
  9     public String readFile(String path) throws IOException {
 10         try (BufferedReader reader = new BufferedReader(new FileReader(path))) {
 11             StringBuilder builder = new StringBuilder();
 12             String line = null;
 13             while ((line = reader.readLine()) != null) {
 14                 builder.append(line);
 15                 builder.append(String.format("%n"));
 16             }
 17             return builder.toString();
 18         }
 19     }
 20 }

实现AutoCloseable

  1 /**
  2  * @author patterncat
  3  * @created 2014-07-21
  4  */
  5 public class CustomResource  implements AutoCloseable {
  6     public void close() throws Exception {
  7         System.out.println("进行资源释放。");
  8     }
  9     public void useCustomResource() throws Exception {
 10         try (CustomResource resource = new CustomResource())  {
 11             System.out.println("使用资源。");
 12         }
 13     }
 14     public static void main(String[] args) {
 15         try {
 16             new CustomResource().useCustomResource();
 17         } catch (Exception ex) {
 18             ex.printStackTrace();
 19         }
 20     }
 21 }

4、JSR341-Expression Language Specification(新规范)

  1 public static void main(String[] args){
  2         ELProcessor el = new ELProcessor();
  3         assert (el.eval("Math.random()") instanceof Double);
  4     }

5、JSR203-More New I/O APIs for the Java Platform(新规范)

• bytebuffer

  1 public class ByteBufferUsage {
  2     public void useByteBuffer() {
  3         ByteBuffer buffer = ByteBuffer.allocate(32);
  4         buffer.put((byte)1);
  5         buffer.put(new byte[3]);
  6         buffer.putChar('A');
  7         buffer.putFloat(0.0f);
  8         buffer.putLong(10, 100L);
  9         System.out.println(buffer.getChar(4));
 10         System.out.println(buffer.remaining());
 11     }
 12     public void byteOrder() {
 13         ByteBuffer buffer = ByteBuffer.allocate(4);
 14         buffer.putInt(1);
 15         buffer.order(ByteOrder.LITTLE_ENDIAN);
 16         buffer.getInt(0); //值为16777216
 17     }
 18     public void compact() {
 19         ByteBuffer buffer = ByteBuffer.allocate(32);
 20         buffer.put(new byte[16]);
 21         buffer.flip();
 22         buffer.getInt();
 23         buffer.compact();
 24         int pos = buffer.position();
 25     }
 26     public void viewBuffer() {
 27         ByteBuffer buffer = ByteBuffer.allocate(32);
 28         buffer.putInt(1);
 29         IntBuffer intBuffer = buffer.asIntBuffer();
 30         intBuffer.put(2);
 31         int value = buffer.getInt(); //值为2
 32     }
 33     /**
 34      * @param args the command line arguments
 35      */
 36     public static void main(String[] args) {
 37         ByteBufferUsage bbu = new ByteBufferUsage();
 38         bbu.useByteBuffer();
 39         bbu.byteOrder();
 40         bbu.compact();
 41         bbu.viewBuffer();
 42     }
 43 }

• filechannel

  1 public class FileChannelUsage {
  2     public void openAndWrite() throws IOException {
  3         FileChannel channel = FileChannel.open(Paths.get("my.txt"), StandardOpenOption.CREATE, StandardOpenOption.WRITE);
  4         ByteBuffer buffer = ByteBuffer.allocate(64);
  5         buffer.putChar('A').flip();
  6         channel.write(buffer);
  7     }
  8     public void readWriteAbsolute() throws IOException {
  9         FileChannel channel = FileChannel.open(Paths.get("absolute.txt"), StandardOpenOption.READ, StandardOpenOption.CREATE, StandardOpenOption.WRITE);
 10         ByteBuffer writeBuffer = ByteBuffer.allocate(4).putChar('A').putChar('B');
 11         writeBuffer.flip();
 12         channel.write(writeBuffer, 1024);
 13         ByteBuffer readBuffer = ByteBuffer.allocate(2);
 14         channel.read(readBuffer, 1026);
 15         readBuffer.flip();
 16         char result = readBuffer.getChar(); //值为'B'
 17     }
 18     /**
 19      * @param args the command line arguments
 20      */
 21     public static void main(String[] args) throws IOException {
 22         FileChannelUsage fcu = new FileChannelUsage();
 23         fcu.openAndWrite();
 24         fcu.readWriteAbsolute();
 25     }
 26 }

6、JSR292与InvokeDynamic

JSR 292: Supporting Dynamically Typed Languages on the JavaTM Platform，支持在JVM上运行动态类型语言。在字节码层面支持了InvokeDynamic。

• 方法句柄MethodHandle

    1 public class ThreadPoolManager {
    2     private final ScheduledExecutorService stpe = Executors
    3             .newScheduledThreadPool(2);
    4     private final BlockingQueue<WorkUnit<String>> lbq;
    5     public ThreadPoolManager(BlockingQueue<WorkUnit<String>> lbq_) {
    6         lbq = lbq_;
    7     }
    8     public ScheduledFuture<?> run(QueueReaderTask msgReader) {
    9         msgReader.setQueue(lbq);
   10         return stpe.scheduleAtFixedRate(msgReader, 10, 10, TimeUnit.MILLISECONDS);
   11     }
   12     private void cancel(final ScheduledFuture<?> hndl) {
   13         stpe.schedule(new Runnable() {
   14             public void run() {
   15                 hndl.cancel(true);
   16             }
   17         }, 10, TimeUnit.MILLISECONDS);
   18     }
   19     /**
   20      * 使用传统的反射api
   21      */
   22     public Method makeReflective() {
   23         Method meth = null;
   24         try {
   25             Class<?>[] argTypes = new Class[]{ScheduledFuture.class};
   26             meth = ThreadPoolManager.class.getDeclaredMethod("cancel", argTypes);
   27             meth.setAccessible(true);
   28         } catch (IllegalArgumentException | NoSuchMethodException
   29                 | SecurityException e) {
   30             e.printStackTrace();
   31         }
   32         return meth;
   33     }
   34     /**
   35      * 使用代理类
   36      * @return
   37      */
   38     public CancelProxy makeProxy() {
   39         return new CancelProxy();
   40     }
   41     /**
   42      * 使用Java7的新api，MethodHandle
   43      * invoke virtual 动态绑定后调用 obj.xxx
   44      * invoke special 静态绑定后调用 super.xxx
   45      * @return
   46      */
   47     public MethodHandle makeMh() {
   48         MethodHandle mh;
   49         MethodType desc = MethodType.methodType(void.class, ScheduledFuture.class);
   50         try {
   51             mh = MethodHandles.lookup().findVirtual(ThreadPoolManager.class,
   52                     "cancel", desc);
   53         } catch (NoSuchMethodException | IllegalAccessException e) {
   54             throw (AssertionError) new AssertionError().initCause(e);
   55         }
   56         return mh;
   57     }
   58     public static class CancelProxy {
   59         private CancelProxy() {
   60         }
   61         public void invoke(ThreadPoolManager mae_, ScheduledFuture<?> hndl_) {
   62             mae_.cancel(hndl_);
   63         }
   64     }
   65 }

• 调用

    1 public class ThreadPoolMain {
    2     /**
    3      * 如果被继承，还能在静态上下文寻找正确的class
    4      */
    5     private static final Logger logger = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());
    6     private ThreadPoolManager manager;
    7     public static void main(String[] args) {
    8         ThreadPoolMain main = new ThreadPoolMain();
    9         main.run();
   10     }
   11     private void cancelUsingReflection(ScheduledFuture<?> hndl) {
   12         Method meth = manager.makeReflective();
   13         try {
   14             System.out.println("With Reflection");
   15             meth.invoke(hndl);
   16         } catch (IllegalAccessException | IllegalArgumentException
   17                 | InvocationTargetException e) {
   18             e.printStackTrace();
   19         }
   20     }
   21     private void cancelUsingProxy(ScheduledFuture<?> hndl) {
   22         CancelProxy proxy = manager.makeProxy();
   23         System.out.println("With Proxy");
   24         proxy.invoke(manager, hndl);
   25     }
   26     private void cancelUsingMH(ScheduledFuture<?> hndl) {
   27         MethodHandle mh = manager.makeMh();
   28         try {
   29             System.out.println("With Method Handle");
   30             mh.invokeExact(manager, hndl);
   31         } catch (Throwable e) {
   32             e.printStackTrace();
   33         }
   34     }
   35     private void run() {
   36         BlockingQueue<WorkUnit<String>> lbq = new LinkedBlockingQueue<>();
   37         manager = new ThreadPoolManager(lbq);
   38         final QueueReaderTask msgReader = new QueueReaderTask(100) {
   39             @Override
   40             public void doAction(String msg_) {
   41                 if (msg_ != null)
   42                     System.out.println("Msg recvd: " + msg_);
   43             }
   44         };
   45         ScheduledFuture<?> hndl = manager.run(msgReader);
   46         cancelUsingMH(hndl);
   47         // cancelUsingProxy(hndl);
   48         // cancelUsingReflection(hndl);
   49     }
   50 }

7、支持JDBC4.1规范

• abort方法

    1 public class AbortConnection {
    2     public void abortConnection() throws SQLException {
    3         Connection connection = DriverManager
    4                 .getConnection("jdbc:derby://localhost/java7book");
    5         ThreadPoolExecutor executor = new DebugExecutorService(2, 10, 60,
    6                 TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>());
    7         connection.abort(executor);
    8         executor.shutdown();
    9         try {
   10             executor.awaitTermination(5, TimeUnit.MINUTES);
   11             System.out.println(executor.getCompletedTaskCount());
   12         } catch (InterruptedException e) {
   13             e.printStackTrace();
   14         }
   15     }
   16     private static class DebugExecutorService extends ThreadPoolExecutor {
   17         public DebugExecutorService(int corePoolSize, int maximumPoolSize,
   18                 long keepAliveTime, TimeUnit unit,
   19                 BlockingQueue<Runnable> workQueue) {
   20             super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue);
   21         }
   22         public void beforeExecute(Thread t, Runnable r) {
   23             System.out.println("清理任务：" + r.getClass());
   24             super.beforeExecute(t, r);
   25         }
   26     }
   27     public static void main(String[] args) {
   28         AbortConnection ca = new AbortConnection();
   29         try {
   30             ca.abortConnection();
   31         } catch (SQLException e) {
   32             e.printStackTrace();
   33         }
   34     }
   35 }

• 自动关闭

    1 public class SetSchema {
    2     public void setSchema() throws SQLException {
    3         try (Connection connection = DriverManager
    4                 .getConnection("jdbc:derby://localhost/java7book")) {
    5             connection.setSchema("DEMO_SCHEMA");
    6             try (Statement stmt = connection.createStatement();
    7                     ResultSet rs = stmt.executeQuery("SELECT * FROM author")) {
    8                 while (rs.next()) {
    9                     System.out.println(rs.getString("name"));
   10                 }
   11             }
   12         }
   13     }
   14     public static void main(String[] args) {
   15         SetSchema ss = new SetSchema();
   16         try {
   17             ss.setSchema();
   18         } catch (SQLException e) {
   19             e.printStackTrace();
   20         }
   21     }
   22 }

• 自动映射

8、Path接口(重要接口更新)

  1 public class PathUsage {
  2     public void usePath() {
  3         Path path1 = Paths.get("folder1", "sub1");
  4         Path path2 = Paths.get("folder2", "sub2");
  5         path1.resolve(path2); //folder1\sub1\folder2\sub2
  6         path1.resolveSibling(path2); //folder1\folder2\sub2
  7         path1.relativize(path2); //..\..\folder2\sub2
  8         path1.subpath(0, 1); //folder1
  9         path1.startsWith(path2); //false
 10         path1.endsWith(path2); //false
 11         Paths.get("folder1/./../folder2/my.text").normalize(); //folder2\my.text
 12     }
 13     /**
 14      * @param args the command line arguments
 15      */
 16     public static void main(String[] args) {
 17         PathUsage usage = new PathUsage();
 18         usage.usePath();
 19     }
 20 }

9、DirectoryStream

  1 public class ListFile {
  2     public void listFiles() throws IOException {
  3         Path path = Paths.get("");
  4         try (DirectoryStream<Path> stream = Files.newDirectoryStream(path, "*.*")) {
  5             for (Path entry: stream) {
  6                 //使用entry
  7                 System.out.println(entry);
  8             }
  9         }
 10     }
 11     /**
 12      * @param args the command line arguments
 13      */
 14     public static void main(String[] args) throws IOException {
 15         ListFile listFile = new ListFile();
 16         listFile.listFiles();
 17     }
 18 }

10、Files

  1 public class FilesUtils {
  2     public void manipulateFiles() throws IOException {
  3         Path newFile = Files.createFile(Paths.get("new.txt").toAbsolutePath());
  4         List<String> content = new ArrayList<String>();
  5         content.add("Hello");
  6         content.add("World");
  7         Files.write(newFile, content, Charset.forName("UTF-8"));
  8         Files.size(newFile);
  9         byte[] bytes = Files.readAllBytes(newFile);
 10         ByteArrayOutputStream output = new ByteArrayOutputStream();
 11         Files.copy(newFile, output);
 12         Files.delete(newFile);
 13     }
 14     /**
 15      * @param args the command line arguments
 16      */
 17     public static void main(String[] args) throws IOException {
 18         FilesUtils fu = new FilesUtils();
 19         fu.manipulateFiles();
 20     }
 21 }

11、WatchService

  1 public class WatchAndCalculate {
  2     public void calculate() throws IOException, InterruptedException {
  3         WatchService service = FileSystems.getDefault().newWatchService();
  4         Path path = Paths.get("").toAbsolutePath();
  5         path.register(service, StandardWatchEventKinds.ENTRY_CREATE);
  6         while (true) {
  7             WatchKey key = service.take();
  8             for (WatchEvent<?> event : key.pollEvents()) {
  9                 Path createdPath = (Path) event.context();
 10                 createdPath = path.resolve(createdPath);
 11                 long size = Files.size(createdPath);
 12                 System.out.println(createdPath + " ==> " + size);
 13             }
 14             key.reset();
 15         }
 16     }
 17     /**
 18      * @param args the command line arguments
 19      */
 20     public static void main(String[] args) throws Throwable {
 21         WatchAndCalculate wc = new WatchAndCalculate();
 22         wc.calculate();
 23     }
 24 }

12、jcmd utility

jcmd是为了替代jps出现了，包含了jps的大部分功能并新增了一些新的功能。

• jcmd -l
  列出所有的Java虚拟机，针对每一个虚拟机可以使用help列出它们支持的命令。

  1 jcmd -l
  2 15308 org.eclipse.jetty.xml.XmlConfiguration /tmp/start4070493346048555702.properties /opt/educat/apps/conf/jetty8.xml
  3 5624 sun.tools.jcmd.JCmd -l
  4 20967 org.apache.flume.node.Application --no-reload-conf -f /opt/educat/flume_agent/conf/flume.conf -n log_agent

• jcmd pid help

  1 jcmd 15308 help
  2 15308:
  3 The following commands are available:
  4 VM.commercial_features
  5 ManagementAgent.stop
  6 ManagementAgent.start_local
  7 ManagementAgent.start
  8 Thread.print
  9 GC.class_histogram
 10 GC.heap_dump
 11 GC.run_finalization
 12 GC.run
 13 VM.uptime
 14 VM.flags
 15 VM.system_properties
 16 VM.command_line
 17 VM.version
 18 help
 19 For more information about a specific command use 'help <command>'.

• jcmd pid VM.flags查看启动参数

  1 jcmd 15308 VM.flags
  2 15308:
  3 -XX:+DisableExplicitGC
  4 -XX:ErrorFile=/var/patterncat/logs/catapp.vmerr.log.201505071655
  5 -XX:+HeapDumpOnOutOfMemoryError
  6 -XX:HeapDumpPath=/var/patterncat/logs/catapp.heaperr.log.201505071655 -XX:InitialHeapSize=5368709120
  7 -XX:+ManagementServer
  8 -XX:MaxGCPauseMillis=100
  9 -XX:MaxHeapSize=5368709120
 10 -XX:MaxPermSize=268435456
 11 -XX:+PrintAdaptiveSizePolicy
 12 -XX:+PrintCommandLineFlags
 13 -XX:+PrintGC
 14 -XX:+PrintGCApplicationStoppedTime
 15 -XX:+PrintGCDateStamps
 16 -XX:+PrintGCDetails
 17 -XX:+PrintGCTimeStamps
 18 -XX:+PrintHeapAtGC
 19 -XX:+PrintTenuringDistribution
 20 -XX:StringTableSize=49999
 21 -XX:+UnlockExperimentalVMOptions
 22 -XX:+UseCompressedOops
 23 -XX:+UseG1GC

• jcmd pid GC.heap_dump D:\d.dump 导出堆信息

• jcmd pid GC.class_histogram查看系统中类的统计信息

• jcmd pid VM.system_properties查看系统属性内容

• jcmd pid Thread.print 打印线程栈

• jcmd pid VM.uptime 查看虚拟机启动时间

• jcmd pid PerfCounter.print 查看性能统计

  1 jcmd 15308 PerfCounter.print
  2 15308:
  3 java.ci.totalTime=79326405
  4 java.cls.loadedClasses=19977
  5 java.cls.sharedLoadedClasses=0
  6 java.cls.sharedUnloadedClasses=0
  7 java.cls.unloadedClasses=1443
  8 java.property.java.class.path="/opt/educat/apps/server/jetty-distribution-8.1.9.v20130131/lib/jetty-xml-8.1.9.v20130131.jar:/opt/educat/apps/server/jetty-distribution-8.1.9.v20130131/lib/servlet-api-3.0.jar:/opt/educat/apps/server/jetty-distribution-8.1.9.v20130131/lib/jetty-http-8.1.9.v20130131.jar:/opt/educat/apps/server/jetty-distribution-8.1.9.v20130131/lib/jetty-continuation-8.1.9.v20130131.jar:/opt/educat/apps/server/jetty-distribution-8.1.9.v20130131/lib/jetty-server-8.1.9.v20130131.jar:/opt/educat/apps/server/jetty-distribution-8.1.9.v20130131/lib/jetty-security-8.1.9.v20130131.jar:/opt/educat/apps/server/jetty-distribution-8.1.9.v20130131/lib/jetty-servlet-8.1.9.v20130131.jar:/opt/educat/apps/server/jetty-distribution-8.1.9.v20130131/lib/jetty-webapp-8.1.9.v20130131.jar:/opt/educat/apps/server/jetty-distribution-8.1.9.v20130131/lib/jetty-deploy-8.1.9.v20130131.jar:/opt/educat/apps/server/jetty-distribution-8.1.9.v20130131/lib/jetty-servlets-8.1.9.v20130131.jar:/opt/educat/apps/server/jetty-distribution-8.1.9.v20130131/l"
  9 java.property.java.endorsed.dirs="/usr/local/jdk1.7.0_21/jre/lib/endorsed"
 10 java.property.java.ext.dirs="/usr/local/jdk1.7.0_21/jre/lib/ext:/usr/java/packages/lib/ext"
 11 java.property.java.home="/usr/local/jdk1.7.0_21/jre"
 12 java.property.java.library.path="/usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib"
 13 java.property.java.version="1.7.0_21"
 14 java.property.java.vm.info="mixed mode"
 15 java.property.java.vm.name="Java HotSpot(TM) 64-Bit Server VM"
 16 java.property.java.vm.specification.name="Java Virtual Machine Specification"
 17 java.property.java.vm.specification.vendor="Oracle Corporation"
 18 java.property.java.vm.specification.version="1.7"
 19 java.property.java.vm.vendor="Oracle Corporation"
 20 java.property.java.vm.version="23.21-b01"
 21 java.rt.vmArgs="-javaagent:/opt/educat/apps/lib/jolokia-jvm-1.1.0-agent.jar=port=23061 -Xloggc:/var/patterncat/logs/catapp.gc.log.201505071655 -XX:ErrorFile=/var/patterncat/logs/catapp.vmerr.log.201505071655 -XX:HeapDumpPath=/var/patterncat/logs/catapp.heaperr.log.201505071655 -Xmx5g -Xms5g -XX:MaxPermSize=256m -XX:+HeapDumpOnOutOfMemoryError -XX:+DisableExplicitGC -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+PrintGCTimeStamps -XX:+PrintGCApplicationStoppedTime -XX:+PrintHeapAtGC -XX:+PrintTenuringDistribution -XX:+PrintCommandLineFlags -XX:+PrintAdaptiveSizePolicy -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:MaxGCPauseMillis=100 -XX:StringTableSize=49999 -Djetty.home=/opt/educat/apps/server/jetty-distribution-8.1.9.v20130131 -Dapp.port=8061 -Dmedis_environment=online -Dcore.step=app -DSTOP.PORT=38061 -Djetty.port=8061 -Dcom.sun.management.jmxremote.authenticate=false -Dapp.logdir=/var/patterncat/logs -DLog4jContextSelector=org.apache.logging.log4j.core.async.AsyncLoggerContextSelector -Dapp.ip=10.64.28.207 -Dapp.cont"
 22 java.rt.vmFlags=""
 23 java.threads.daemon=72
 24 java.threads.live=128
 25 java.threads.livePeak=129
 26 java.threads.started=1444
 27 sun.ci.compilerThread.0.compiles=2595
 28 sun.ci.compilerThread.0.method=""
 29 sun.ci.compilerThread.0.time=1290
 30 sun.ci.compilerThread.0.type=1
 31 sun.ci.compilerThread.1.compiles=2802
 32 sun.ci.compilerThread.1.method=""
 33 sun.ci.compilerThread.1.time=1413
 34 sun.ci.compilerThread.1.type=2
 35 sun.ci.lastFailedMethod=""
 36 sun.ci.lastFailedType=0
 37 sun.ci.lastInvalidatedMethod=""
 38 sun.ci.lastInvalidatedType=0
 39 sun.ci.lastMethod="org/codehaus/groovy/classgen/VariableScopeVisitor checkVariableNameForDeclaration"
 40 sun.ci.lastSize=2184
 41 sun.ci.lastType=1
 42 sun.ci.nmethodCodeSize=12188576
 43 sun.ci.nmethodSize=24492688
 44 sun.ci.osrBytes=196694
 45 sun.ci.osrCompiles=156
 46 sun.ci.osrTime=8521713
 47 sun.ci.standardBytes=2072839
 48 sun.ci.standardCompiles=5241
 49 sun.ci.standardTime=70804692
 50 sun.ci.threads=2
 51 sun.ci.totalBailouts=0
 52 sun.ci.totalCompiles=5397
 53 sun.ci.totalInvalidates=0
 54 sun.classloader.findClassTime=358334873
 55 sun.classloader.findClasses=507
 56 sun.classloader.parentDelegationTime=30062667
 57 sun.cls.appClassBytes=63743816
 58 sun.cls.appClassLoadCount=58098
 59 sun.cls.appClassLoadTime=9843833
 60 sun.cls.appClassLoadTime.self=5288490
 61 sun.cls.classInitTime=2617049
 62 sun.cls.classInitTime.self=1088905
 63 sun.cls.classLinkedTime=4605704
 64 sun.cls.classLinkedTime.self=541928
 65 sun.cls.classVerifyTime=4055324
 66 sun.cls.classVerifyTime.self=2423448
 67 sun.cls.defineAppClassTime=3206202
 68 sun.cls.defineAppClassTime.self=386302
 69 sun.cls.defineAppClasses=16465
 70 sun.cls.initializedClasses=14546
 71 sun.cls.isUnsyncloadClassSet=0
 72 sun.cls.jniDefineClassNoLockCalls=94
 73 sun.cls.jvmDefineClassNoLockCalls=4405
 74 sun.cls.jvmFindLoadedClassNoLockCalls=32671
 75 sun.cls.linkedClasses=16465
 76 sun.cls.loadInstanceClassFailRate=0
 77 sun.cls.loadedBytes=43314456
 78 sun.cls.lookupSysClassTime=87247
 79 sun.cls.methodBytes=34262690
 80 sun.cls.nonSystemLoaderLockContentionRate=133
 81 sun.cls.parseClassTime=3099390
 82 sun.cls.parseClassTime.self=2670584
 83 sun.cls.sharedClassLoadTime=9647
 84 sun.cls.sharedLoadedBytes=0
 85 sun.cls.sharedUnloadedBytes=0
 86 sun.cls.sysClassBytes=12986737
 87 sun.cls.sysClassLoadTime=503885
 88 sun.cls.systemLoaderLockContentionRate=0
 89 sun.cls.time=15382336
 90 sun.cls.unloadedBytes=5087120
 91 sun.cls.unsafeDefineClassCalls=1555
 92 sun.cls.verifiedClasses=16383
 93 sun.gc.cause="No GC"
 94 sun.gc.collector.0.invocations=85
 95 sun.gc.collector.0.lastEntryTime=24164511065
 96 sun.gc.collector.0.lastExitTime=24164628388
 97 sun.gc.collector.0.name="G1 incremental collections"
 98 sun.gc.collector.0.time=7628099
 99 sun.gc.collector.1.invocations=1
100 sun.gc.collector.1.lastEntryTime=24543200515
101 sun.gc.collector.1.lastExitTime=24544107869
102 sun.gc.collector.1.name="G1 stop-the-world full collections"
103 sun.gc.collector.1.time=907355
104 sun.gc.generation.0.agetable.bytes.00=0
105 sun.gc.generation.0.agetable.bytes.01=4294976
106 sun.gc.generation.0.agetable.bytes.02=2014880
107 sun.gc.generation.0.agetable.bytes.03=5406352
108 sun.gc.generation.0.agetable.bytes.04=4875176
109 sun.gc.generation.0.agetable.bytes.05=2865952
110 sun.gc.generation.0.agetable.bytes.06=4374048
111 sun.gc.generation.0.agetable.bytes.07=2058664
112 sun.gc.generation.0.agetable.bytes.08=3574376
113 sun.gc.generation.0.agetable.bytes.09=6923448
114 sun.gc.generation.0.agetable.bytes.10=1541088
115 sun.gc.generation.0.agetable.bytes.11=1347376
116 sun.gc.generation.0.agetable.bytes.12=735888
117 sun.gc.generation.0.agetable.bytes.13=402632
118 sun.gc.generation.0.agetable.bytes.14=713272
119 sun.gc.generation.0.agetable.bytes.15=728688
120 sun.gc.generation.0.agetable.size=16
121 sun.gc.generation.0.capacity=4510973976
122 sun.gc.generation.0.maxCapacity=5368709144
123 sun.gc.generation.0.minCapacity=24
124 sun.gc.generation.0.name="young"
125 sun.gc.generation.0.space.0.capacity=4510973960
126 sun.gc.generation.0.space.0.initCapacity=1128267784
127 sun.gc.generation.0.space.0.maxCapacity=5368709128
128 sun.gc.generation.0.space.0.name="eden"
129 sun.gc.generation.0.space.0.used=580911104
130 sun.gc.generation.0.space.1.capacity=8
131 sun.gc.generation.0.space.1.initCapacity=8
132 sun.gc.generation.0.space.1.maxCapacity=8
133 sun.gc.generation.0.space.1.name="s0"
134 sun.gc.generation.0.space.1.used=0
135 sun.gc.generation.0.space.2.capacity=8
136 sun.gc.generation.0.space.2.initCapacity=8
137 sun.gc.generation.0.space.2.maxCapacity=5368709128
138 sun.gc.generation.0.space.2.name="s1"
139 sun.gc.generation.0.space.2.used=0
140 sun.gc.generation.0.spaces=3
141 sun.gc.generation.1.capacity=857735176
142 sun.gc.generation.1.maxCapacity=5368709128
143 sun.gc.generation.1.minCapacity=8
144 sun.gc.generation.1.name="old"
145 sun.gc.generation.1.space.0.capacity=857735176
146 sun.gc.generation.1.space.0.initCapacity=4240441352
147 sun.gc.generation.1.space.0.maxCapacity=5368709128
148 sun.gc.generation.1.space.0.name="space"
149 sun.gc.generation.1.space.0.used=155730608
150 sun.gc.generation.1.spaces=1
151 sun.gc.generation.2.capacity=138412032
152 sun.gc.generation.2.maxCapacity=268435456
153 sun.gc.generation.2.minCapacity=20971520
154 sun.gc.generation.2.name="perm"
155 sun.gc.generation.2.space.0.capacity=138412032
156 sun.gc.generation.2.space.0.initCapacity=20971520
157 sun.gc.generation.2.space.0.maxCapacity=268435456
158 sun.gc.generation.2.space.0.name="perm"
159 sun.gc.generation.2.space.0.used=138212560
160 sun.gc.generation.2.spaces=1
161 sun.gc.lastCause="Heap Inspection Initiated GC"
162 sun.gc.policy.collectors=1
163 sun.gc.policy.desiredSurvivorSize=264241152
164 sun.gc.policy.generations=3
165 sun.gc.policy.maxTenuringThreshold=15
166 sun.gc.policy.name="GarbageFirst"
167 sun.gc.policy.tenuringThreshold=15
168 sun.gc.tlab.alloc=0
169 sun.gc.tlab.allocThreads=0
170 sun.gc.tlab.fastWaste=0
171 sun.gc.tlab.fills=0
172 sun.gc.tlab.gcWaste=0
173 sun.gc.tlab.maxFastWaste=0
174 sun.gc.tlab.maxFills=0
175 sun.gc.tlab.maxGcWaste=0
176 sun.gc.tlab.maxSlowAlloc=0
177 sun.gc.tlab.maxSlowWaste=0
178 sun.gc.tlab.slowAlloc=0
179 sun.gc.tlab.slowWaste=0
180 sun.management.JMXConnectorServer.0.authenticate="false"
181 sun.management.JMXConnectorServer.0.remoteAddress="service:jmx:rmi:///jndi/rmi://edu-cat02.lf.patterncat.com:8199/jmxrmi"
182 sun.management.JMXConnectorServer.0.ssl="false"
183 sun.management.JMXConnectorServer.0.sslNeedClientAuth="false"
184 sun.management.JMXConnectorServer.0.sslRegistry="false"
185 sun.management.JMXConnectorServer.address="service:jmx:rmi://127.0.0.1/stub/rO0ABXNyAC5qYXZheC5tYW5hZ2VtZW50LnJlbW90ZS5ybWkuUk1JU2VydmVySW1wbF9TdHViAAAAAAAAAAICAAB4cgAaamF2YS5ybWkuc2VydmVyLlJlbW90ZVN0dWLp/tzJi+FlGgIAAHhyABxqYXZhLnJtaS5zZXJ2ZXIuUmVtb3RlT2JqZWN002G0kQxhMx4DAAB4cHc3AAtVbmljYXN0UmVmMgAADDEwLjY0LjI4LjIwNwAAhbjWmVwaDwiNg3l3YeUAAAFNLZX68oACAHg="
186 sun.os.hrt.frequency=1000000
187 sun.os.hrt.ticks=24580753795
188 sun.perfdata.majorVersion=2
189 sun.perfdata.minorVersion=0
190 sun.perfdata.overflow=0
191 sun.perfdata.size=32768
192 sun.perfdata.timestamp=259316
193 sun.perfdata.used=17792
194 sun.property.sun.boot.class.path="/usr/local/jdk1.7.0_21/jre/lib/resources.jar:/usr/local/jdk1.7.0_21/jre/lib/rt.jar:/usr/local/jdk1.7.0_21/jre/lib/sunrsasign.jar:/usr/local/jdk1.7.0_21/jre/lib/jsse.jar:/usr/local/jdk1.7.0_21/jre/lib/jce.jar:/usr/local/jdk1.7.0_21/jre/lib/charsets.jar:/usr/local/jdk1.7.0_21/jre/lib/jfr.jar:/usr/local/jdk1.7.0_21/jre/classes"
195 sun.property.sun.boot.library.path="/usr/local/jdk1.7.0_21/jre/lib/amd64"
196 sun.rt._sync_ContendedLockAttempts=297851
197 sun.rt._sync_Deflations=438863
198 sun.rt._sync_EmptyNotifications=0
199 sun.rt._sync_FailedSpins=0
200 sun.rt._sync_FutileWakeups=349651
201 sun.rt._sync_Inflations=438971
202 sun.rt._sync_MonExtant=16256
203 sun.rt._sync_MonInCirculation=0
204 sun.rt._sync_MonScavenged=0
205 sun.rt._sync_Notifications=1580811
206 sun.rt._sync_Parks=1935145
207 sun.rt._sync_PrivateA=0
208 sun.rt._sync_PrivateB=0
209 sun.rt._sync_SlowEnter=0
210 sun.rt._sync_SlowExit=0
211 sun.rt._sync_SlowNotify=0
212 sun.rt._sync_SlowNotifyAll=0
213 sun.rt._sync_SuccessfulSpins=0
214 sun.rt.applicationTime=24559855809
215 sun.rt.createVmBeginTime=1430988913170
216 sun.rt.createVmEndTime=1430988913429
217 sun.rt.internalVersion="Java HotSpot(TM) 64-Bit Server VM (23.21-b01) for linux-amd64 JRE (1.7.0_21-b11), built on Apr  4 2013 04:03:29 by "java_re" with gcc 4.3.0 20080428 (Red Hat 4.3.0-8)"
218 sun.rt.interruptedBeforeIO=0
219 sun.rt.interruptedDuringIO=0
220 sun.rt.javaCommand="org.eclipse.jetty.xml.XmlConfiguration /tmp/start4070493346048555702.properties /opt/educat/apps/conf/jetty8.xml"
221 sun.rt.jvmCapabilities="1000000000000000000000000000000000000000000000000000000000000000"
222 sun.rt.jvmVersion=387252225
223 sun.rt.safepointSyncTime=2333795
224 sun.rt.safepointTime=15955181
225 sun.rt.safepoints=18365
226 sun.rt.threadInterruptSignaled=0
227 sun.rt.vmInitDoneTime=1430988913232
228 sun.threads.vmOperationTime=9516621
229 sun.urlClassLoader.readClassBytesTime=958824201
230 sun.zip.zipFile.openTime=72163038
231 sun.zip.zipFiles=3838

13、fork/join

Java7提供的一个用于并行执行任务的框架，是一个把大任务分割成若干个小任务，最终汇总每个小任务结果后得到大任务结果的框架。

14、Java Mission Control

在JDK7u40里头提供了Java Mission Control，这个是从JRockit虚拟机里头迁移过来的类似JVisualVm的东东。

15、其他

• Binary Literals支持

• Numeric Literals的下划线支持

• Strings in switch Statements

参考

• Java SE 7 Features and Enhancements

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