Java7的新特性

RicMcReynol 8年前

来自： https://segmentfault.com/a/1190000004417830

Java语言特性系列

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 ) 

/**   * 记录异常，不被淹没   * addSuppressed   */  class ReadFile {      public void read(String filename) throws BaseException {          FileInputStream input = null;          IOException readException = null;          try {              input = new FileInputStream(filename);          } catch (IOException ex) {              readException = ex;          } finally {              if (input != null) {                  try {                      input.close();                  } catch (IOException ex) {                      if (readException == null) {                          readException = ex;                      }else{                          //使用java7的                          readException.addSuppressed(ex);                      }                  }              }              if (readException != null) {                  throw new BaseException(readException);              }          }      }  }

2、捕获多个异常( 新语法 ) 

public void handle() {          ExceptionThrower thrower = new ExceptionThrower();          try {              thrower.manyExceptions();          } catch (ExceptionA | ExceptionB ab) {              System.out.println(ab.getClass());          } catch (ExceptionC c) {          }      }

3、try-with-resources( 新语法 ) 

/**   * try-with-resource   * 不需要使用finally来保证打开的流被正确关闭   * 这是自动完成的。   * @author patterncat   * @created 2014-07-21   */  public class ResourceBasicUsage {      public String readFile(String path) throws IOException {          try (BufferedReader reader = new BufferedReader(new FileReader(path))) {              StringBuilder builder = new StringBuilder();              String line = null;              while ((line = reader.readLine()) != null) {                  builder.append(line);                  builder.append(String.format("%n"));              }              return builder.toString();          }      }  }

实现AutoCloseable

/**   * @author patterncat   * @created 2014-07-21   */  public class CustomResource  implements AutoCloseable {      public void close() throws Exception {          System.out.println("进行资源释放。");      }      public void useCustomResource() throws Exception {          try (CustomResource resource = new CustomResource())  {              System.out.println("使用资源。");          }      }      public static void main(String[] args) {          try {              new CustomResource().useCustomResource();          } catch (Exception ex) {              ex.printStackTrace();          }      }  }

4、JSR341-Expression Language Specification( 新规范 ) 

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

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

  • bytebuffer

public class ByteBufferUsage {      public void useByteBuffer() {          ByteBuffer buffer = ByteBuffer.allocate(32);          buffer.put((byte)1);          buffer.put(new byte[3]);          buffer.putChar('A');          buffer.putFloat(0.0f);          buffer.putLong(10, 100L);          System.out.println(buffer.getChar(4));          System.out.println(buffer.remaining());      }      public void byteOrder() {          ByteBuffer buffer = ByteBuffer.allocate(4);          buffer.putInt(1);          buffer.order(ByteOrder.LITTLE_ENDIAN);          buffer.getInt(0); //值为16777216      }      public void compact() {          ByteBuffer buffer = ByteBuffer.allocate(32);          buffer.put(new byte[16]);          buffer.flip();          buffer.getInt();          buffer.compact();          int pos = buffer.position();      }      public void viewBuffer() {          ByteBuffer buffer = ByteBuffer.allocate(32);          buffer.putInt(1);          IntBuffer intBuffer = buffer.asIntBuffer();          intBuffer.put(2);          int value = buffer.getInt(); //值为2      }      /**       * @param args the command line arguments       */      public static void main(String[] args) {          ByteBufferUsage bbu = new ByteBufferUsage();          bbu.useByteBuffer();          bbu.byteOrder();          bbu.compact();          bbu.viewBuffer();      }  }

  • filechannel

public class FileChannelUsage {      public void openAndWrite() throws IOException {          FileChannel channel = FileChannel.open(Paths.get("my.txt"), StandardOpenOption.CREATE, StandardOpenOption.WRITE);          ByteBuffer buffer = ByteBuffer.allocate(64);          buffer.putChar('A').flip();          channel.write(buffer);      }      public void readWriteAbsolute() throws IOException {          FileChannel channel = FileChannel.open(Paths.get("absolute.txt"), StandardOpenOption.READ, StandardOpenOption.CREATE, StandardOpenOption.WRITE);          ByteBuffer writeBuffer = ByteBuffer.allocate(4).putChar('A').putChar('B');          writeBuffer.flip();          channel.write(writeBuffer, 1024);          ByteBuffer readBuffer = ByteBuffer.allocate(2);          channel.read(readBuffer, 1026);          readBuffer.flip();          char result = readBuffer.getChar(); //值为'B'      }      /**       * @param args the command line arguments       */      public static void main(String[] args) throws IOException {          FileChannelUsage fcu = new FileChannelUsage();          fcu.openAndWrite();          fcu.readWriteAbsolute();      }  }

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

public class ThreadPoolManager {      private final ScheduledExecutorService stpe = Executors              .newScheduledThreadPool(2);      private final BlockingQueue<WorkUnit<String>> lbq;      public ThreadPoolManager(BlockingQueue<WorkUnit<String>> lbq_) {          lbq = lbq_;      }      public ScheduledFuture<?> run(QueueReaderTask msgReader) {          msgReader.setQueue(lbq);          return stpe.scheduleAtFixedRate(msgReader, 10, 10, TimeUnit.MILLISECONDS);      }      private void cancel(final ScheduledFuture<?> hndl) {          stpe.schedule(new Runnable() {              public void run() {                  hndl.cancel(true);              }          }, 10, TimeUnit.MILLISECONDS);      }      /**       * 使用传统的反射api       */      public Method makeReflective() {          Method meth = null;          try {              Class<?>[] argTypes = new Class[]{ScheduledFuture.class};              meth = ThreadPoolManager.class.getDeclaredMethod("cancel", argTypes);              meth.setAccessible(true);          } catch (IllegalArgumentException | NoSuchMethodException                  | SecurityException e) {              e.printStackTrace();          }          return meth;      }      /**       * 使用代理类       * @return       */      public CancelProxy makeProxy() {          return new CancelProxy();      }      /**       * 使用Java7的新api，MethodHandle       * invoke virtual 动态绑定后调用 obj.xxx       * invoke special 静态绑定后调用 super.xxx       * @return       */      public MethodHandle makeMh() {          MethodHandle mh;          MethodType desc = MethodType.methodType(void.class, ScheduledFuture.class);          try {              mh = MethodHandles.lookup().findVirtual(ThreadPoolManager.class,                      "cancel", desc);          } catch (NoSuchMethodException | IllegalAccessException e) {              throw (AssertionError) new AssertionError().initCause(e);          }          return mh;      }      public static class CancelProxy {          private CancelProxy() {          }          public void invoke(ThreadPoolManager mae_, ScheduledFuture<?> hndl_) {              mae_.cancel(hndl_);          }      }  }

  • 调用

public class ThreadPoolMain {      /**       * 如果被继承，还能在静态上下文寻找正确的class       */      private static final Logger logger = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());      private ThreadPoolManager manager;      public static void main(String[] args) {          ThreadPoolMain main = new ThreadPoolMain();          main.run();      }      private void cancelUsingReflection(ScheduledFuture<?> hndl) {          Method meth = manager.makeReflective();          try {              System.out.println("With Reflection");              meth.invoke(hndl);          } catch (IllegalAccessException | IllegalArgumentException                  | InvocationTargetException e) {              e.printStackTrace();          }      }      private void cancelUsingProxy(ScheduledFuture<?> hndl) {          CancelProxy proxy = manager.makeProxy();          System.out.println("With Proxy");          proxy.invoke(manager, hndl);      }      private void cancelUsingMH(ScheduledFuture<?> hndl) {          MethodHandle mh = manager.makeMh();          try {              System.out.println("With Method Handle");              mh.invokeExact(manager, hndl);          } catch (Throwable e) {              e.printStackTrace();          }      }      private void run() {          BlockingQueue<WorkUnit<String>> lbq = new LinkedBlockingQueue<>();          manager = new ThreadPoolManager(lbq);          final QueueReaderTask msgReader = new QueueReaderTask(100) {              @Override              public void doAction(String msg_) {                  if (msg_ != null)                      System.out.println("Msg recvd: " + msg_);              }          };          ScheduledFuture<?> hndl = manager.run(msgReader);          cancelUsingMH(hndl);          // cancelUsingProxy(hndl);          // cancelUsingReflection(hndl);      }  }

7、支持JDBC4.1规范

  • abort方法

public class AbortConnection {      public void abortConnection() throws SQLException {          Connection connection = DriverManager                  .getConnection("jdbc:derby://localhost/java7book");          ThreadPoolExecutor executor = new DebugExecutorService(2, 10, 60,                  TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>());          connection.abort(executor);          executor.shutdown();          try {              executor.awaitTermination(5, TimeUnit.MINUTES);              System.out.println(executor.getCompletedTaskCount());          } catch (InterruptedException e) {              e.printStackTrace();          }      }      private static class DebugExecutorService extends ThreadPoolExecutor {          public DebugExecutorService(int corePoolSize, int maximumPoolSize,                  long keepAliveTime, TimeUnit unit,                  BlockingQueue<Runnable> workQueue) {              super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue);          }          public void beforeExecute(Thread t, Runnable r) {              System.out.println("清理任务：" + r.getClass());              super.beforeExecute(t, r);          }      }      public static void main(String[] args) {          AbortConnection ca = new AbortConnection();          try {              ca.abortConnection();          } catch (SQLException e) {              e.printStackTrace();          }      }  }

  • 自动关闭

public class SetSchema {      public void setSchema() throws SQLException {          try (Connection connection = DriverManager                  .getConnection("jdbc:derby://localhost/java7book")) {              connection.setSchema("DEMO_SCHEMA");              try (Statement stmt = connection.createStatement();                      ResultSet rs = stmt.executeQuery("SELECT * FROM author")) {                  while (rs.next()) {                      System.out.println(rs.getString("name"));                  }              }          }      }      public static void main(String[] args) {          SetSchema ss = new SetSchema();          try {              ss.setSchema();          } catch (SQLException e) {              e.printStackTrace();          }      }  }

  • 自动映射

public class UseSQLData {            public void useSQLData() throws SQLException {          try (Connection connection = DriverManager                  .getConnection("jdbc:derby://localhost/java7book")) {              Map<String,Class<?>> typeMap = new HashMap<String,Class<?>>();              typeMap.put("java7book.Book", Book.class);              try (Statement stmt = connection.createStatement();                      ResultSet rs = stmt.executeQuery("SELECT * FROM book")) {                  while (rs.next()) {                      System.out.println(rs.getObject(1, Book.class));                  }              }          }      }            public static void main(String[] args) {          UseSQLData usd = new UseSQLData();          try {              usd.useSQLData();          } catch (SQLException e) {              e.printStackTrace();          }      }  }

8、Path接口( 重要接口更新 ) 

public class PathUsage {      public void usePath() {          Path path1 = Paths.get("folder1", "sub1");          Path path2 = Paths.get("folder2", "sub2");          path1.resolve(path2); //folder1\sub1\folder2\sub2          path1.resolveSibling(path2); //folder1\folder2\sub2          path1.relativize(path2); //..\..\folder2\sub2          path1.subpath(0, 1); //folder1          path1.startsWith(path2); //false          path1.endsWith(path2); //false          Paths.get("folder1/./../folder2/my.text").normalize(); //folder2\my.text      }      /**       * @param args the command line arguments       */      public static void main(String[] args) {          PathUsage usage = new PathUsage();          usage.usePath();      }  }

9、DirectoryStream

public class ListFile {      public void listFiles() throws IOException {          Path path = Paths.get("");          try (DirectoryStream<Path> stream = Files.newDirectoryStream(path, "*.*")) {              for (Path entry: stream) {                  //使用entry                  System.out.println(entry);              }          }      }      /**       * @param args the command line arguments       */      public static void main(String[] args) throws IOException {          ListFile listFile = new ListFile();          listFile.listFiles();      }  }

10、Files

public class FilesUtils {      public void manipulateFiles() throws IOException {          Path newFile = Files.createFile(Paths.get("new.txt").toAbsolutePath());          List<String> content = new ArrayList<String>();          content.add("Hello");          content.add("World");          Files.write(newFile, content, Charset.forName("UTF-8"));          Files.size(newFile);          byte[] bytes = Files.readAllBytes(newFile);          ByteArrayOutputStream output = new ByteArrayOutputStream();          Files.copy(newFile, output);          Files.delete(newFile);      }      /**       * @param args the command line arguments       */      public static void main(String[] args) throws IOException {          FilesUtils fu = new FilesUtils();          fu.manipulateFiles();      }  }

11、WatchService

public class WatchAndCalculate {      public void calculate() throws IOException, InterruptedException {          WatchService service = FileSystems.getDefault().newWatchService();          Path path = Paths.get("").toAbsolutePath();          path.register(service, StandardWatchEventKinds.ENTRY_CREATE);          while (true) {              WatchKey key = service.take();              for (WatchEvent<?> event : key.pollEvents()) {                  Path createdPath = (Path) event.context();                  createdPath = path.resolve(createdPath);                  long size = Files.size(createdPath);                  System.out.println(createdPath + " ==> " + size);              }              key.reset();          }      }      /**       * @param args the command line arguments       */      public static void main(String[] args) throws Throwable {          WatchAndCalculate wc = new WatchAndCalculate();          wc.calculate();      }  }

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。 

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

  • jcmd pid help

jcmd 15308 help  15308:  The following commands are available:  VM.commercial_features  ManagementAgent.stop  ManagementAgent.start_local  ManagementAgent.start  Thread.print  GC.class_histogram  GC.heap_dump  GC.run_finalization  GC.run  VM.uptime  VM.flags  VM.system_properties  VM.command_line  VM.version  help  For more information about a specific command use 'help <command>'.

  • jcmd pid VM.flags查看启动参数

jcmd 15308 VM.flags  15308:  -XX:+DisableExplicitGC   -XX:ErrorFile=/var/patterncat/logs/catapp.vmerr.log.201505071655   -XX:+HeapDumpOnOutOfMemoryError   -XX:HeapDumpPath=/var/patterncat/logs/catapp.heaperr.log.201505071655 -XX:InitialHeapSize=5368709120   -XX:+ManagementServer   -XX:MaxGCPauseMillis=100   -XX:MaxHeapSize=5368709120   -XX:MaxPermSize=268435456   -XX:+PrintAdaptiveSizePolicy   -XX:+PrintCommandLineFlags   -XX:+PrintGC   -XX:+PrintGCApplicationStoppedTime   -XX:+PrintGCDateStamps   -XX:+PrintGCDetails   -XX:+PrintGCTimeStamps   -XX:+PrintHeapAtGC   -XX:+PrintTenuringDistribution   -XX:StringTableSize=49999   -XX:+UnlockExperimentalVMOptions   -XX:+UseCompressedOops   -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

jcmd 15308 PerfCounter.print  15308:  java.ci.totalTime=79326405  java.cls.loadedClasses=19977  java.cls.sharedLoadedClasses=0  java.cls.sharedUnloadedClasses=0  java.cls.unloadedClasses=1443  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"  java.property.java.endorsed.dirs="/usr/local/jdk1.7.0_21/jre/lib/endorsed"  java.property.java.ext.dirs="/usr/local/jdk1.7.0_21/jre/lib/ext:/usr/java/packages/lib/ext"  java.property.java.home="/usr/local/jdk1.7.0_21/jre"  java.property.java.library.path="/usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib"  java.property.java.version="1.7.0_21"  java.property.java.vm.info="mixed mode"  java.property.java.vm.name="Java HotSpot(TM) 64-Bit Server VM"  java.property.java.vm.specification.name="Java Virtual Machine Specification"  java.property.java.vm.specification.vendor="Oracle Corporation"  java.property.java.vm.specification.version="1.7"  java.property.java.vm.vendor="Oracle Corporation"  java.property.java.vm.version="23.21-b01"  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"  java.rt.vmFlags=""  java.threads.daemon=72  java.threads.live=128  java.threads.livePeak=129  java.threads.started=1444  sun.ci.compilerThread.0.compiles=2595  sun.ci.compilerThread.0.method=""  sun.ci.compilerThread.0.time=1290  sun.ci.compilerThread.0.type=1  sun.ci.compilerThread.1.compiles=2802  sun.ci.compilerThread.1.method=""  sun.ci.compilerThread.1.time=1413  sun.ci.compilerThread.1.type=2  sun.ci.lastFailedMethod=""  sun.ci.lastFailedType=0  sun.ci.lastInvalidatedMethod=""  sun.ci.lastInvalidatedType=0  sun.ci.lastMethod="org/codehaus/groovy/classgen/VariableScopeVisitor checkVariableNameForDeclaration"  sun.ci.lastSize=2184  sun.ci.lastType=1  sun.ci.nmethodCodeSize=12188576  sun.ci.nmethodSize=24492688  sun.ci.osrBytes=196694  sun.ci.osrCompiles=156  sun.ci.osrTime=8521713  sun.ci.standardBytes=2072839  sun.ci.standardCompiles=5241  sun.ci.standardTime=70804692  sun.ci.threads=2  sun.ci.totalBailouts=0  sun.ci.totalCompiles=5397  sun.ci.totalInvalidates=0  sun.classloader.findClassTime=358334873  sun.classloader.findClasses=507  sun.classloader.parentDelegationTime=30062667  sun.cls.appClassBytes=63743816  sun.cls.appClassLoadCount=58098  sun.cls.appClassLoadTime=9843833  sun.cls.appClassLoadTime.self=5288490  sun.cls.classInitTime=2617049  sun.cls.classInitTime.self=1088905  sun.cls.classLinkedTime=4605704  sun.cls.classLinkedTime.self=541928  sun.cls.classVerifyTime=4055324  sun.cls.classVerifyTime.self=2423448  sun.cls.defineAppClassTime=3206202  sun.cls.defineAppClassTime.self=386302  sun.cls.defineAppClasses=16465  sun.cls.initializedClasses=14546  sun.cls.isUnsyncloadClassSet=0  sun.cls.jniDefineClassNoLockCalls=94  sun.cls.jvmDefineClassNoLockCalls=4405  sun.cls.jvmFindLoadedClassNoLockCalls=32671  sun.cls.linkedClasses=16465  sun.cls.loadInstanceClassFailRate=0  sun.cls.loadedBytes=43314456  sun.cls.lookupSysClassTime=87247  sun.cls.methodBytes=34262690  sun.cls.nonSystemLoaderLockContentionRate=133  sun.cls.parseClassTime=3099390  sun.cls.parseClassTime.self=2670584  sun.cls.sharedClassLoadTime=9647  sun.cls.sharedLoadedBytes=0  sun.cls.sharedUnloadedBytes=0  sun.cls.sysClassBytes=12986737  sun.cls.sysClassLoadTime=503885  sun.cls.systemLoaderLockContentionRate=0  sun.cls.time=15382336  sun.cls.unloadedBytes=5087120  sun.cls.unsafeDefineClassCalls=1555  sun.cls.verifiedClasses=16383  sun.gc.cause="No GC"  sun.gc.collector.0.invocations=85  sun.gc.collector.0.lastEntryTime=24164511065  sun.gc.collector.0.lastExitTime=24164628388  sun.gc.collector.0.name="G1 incremental collections"  sun.gc.collector.0.time=7628099  sun.gc.collector.1.invocations=1  sun.gc.collector.1.lastEntryTime=24543200515  sun.gc.collector.1.lastExitTime=24544107869  sun.gc.collector.1.name="G1 stop-the-world full collections"  sun.gc.collector.1.time=907355  sun.gc.generation.0.agetable.bytes.00=0  sun.gc.generation.0.agetable.bytes.01=4294976  sun.gc.generation.0.agetable.bytes.02=2014880  sun.gc.generation.0.agetable.bytes.03=5406352  sun.gc.generation.0.agetable.bytes.04=4875176  sun.gc.generation.0.agetable.bytes.05=2865952  sun.gc.generation.0.agetable.bytes.06=4374048  sun.gc.generation.0.agetable.bytes.07=2058664  sun.gc.generation.0.agetable.bytes.08=3574376  sun.gc.generation.0.agetable.bytes.09=6923448  sun.gc.generation.0.agetable.bytes.10=1541088  sun.gc.generation.0.agetable.bytes.11=1347376  sun.gc.generation.0.agetable.bytes.12=735888  sun.gc.generation.0.agetable.bytes.13=402632  sun.gc.generation.0.agetable.bytes.14=713272  sun.gc.generation.0.agetable.bytes.15=728688  sun.gc.generation.0.agetable.size=16  sun.gc.generation.0.capacity=4510973976  sun.gc.generation.0.maxCapacity=5368709144  sun.gc.generation.0.minCapacity=24  sun.gc.generation.0.name="young"  sun.gc.generation.0.space.0.capacity=4510973960  sun.gc.generation.0.space.0.initCapacity=1128267784  sun.gc.generation.0.space.0.maxCapacity=5368709128  sun.gc.generation.0.space.0.name="eden"  sun.gc.generation.0.space.0.used=580911104  sun.gc.generation.0.space.1.capacity=8  sun.gc.generation.0.space.1.initCapacity=8  sun.gc.generation.0.space.1.maxCapacity=8  sun.gc.generation.0.space.1.name="s0"  sun.gc.generation.0.space.1.used=0  sun.gc.generation.0.space.2.capacity=8  sun.gc.generation.0.space.2.initCapacity=8  sun.gc.generation.0.space.2.maxCapacity=5368709128  sun.gc.generation.0.space.2.name="s1"  sun.gc.generation.0.space.2.used=0  sun.gc.generation.0.spaces=3  sun.gc.generation.1.capacity=857735176  sun.gc.generation.1.maxCapacity=5368709128  sun.gc.generation.1.minCapacity=8  sun.gc.generation.1.name="old"  sun.gc.generation.1.space.0.capacity=857735176  sun.gc.generation.1.space.0.initCapacity=4240441352  sun.gc.generation.1.space.0.maxCapacity=5368709128  sun.gc.generation.1.space.0.name="space"  sun.gc.generation.1.space.0.used=155730608  sun.gc.generation.1.spaces=1  sun.gc.generation.2.capacity=138412032  sun.gc.generation.2.maxCapacity=268435456  sun.gc.generation.2.minCapacity=20971520  sun.gc.generation.2.name="perm"  sun.gc.generation.2.space.0.capacity=138412032  sun.gc.generation.2.space.0.initCapacity=20971520  sun.gc.generation.2.space.0.maxCapacity=268435456  sun.gc.generation.2.space.0.name="perm"  sun.gc.generation.2.space.0.used=138212560  sun.gc.generation.2.spaces=1  sun.gc.lastCause="Heap Inspection Initiated GC"  sun.gc.policy.collectors=1  sun.gc.policy.desiredSurvivorSize=264241152  sun.gc.policy.generations=3  sun.gc.policy.maxTenuringThreshold=15  sun.gc.policy.name="GarbageFirst"  sun.gc.policy.tenuringThreshold=15  sun.gc.tlab.alloc=0  sun.gc.tlab.allocThreads=0  sun.gc.tlab.fastWaste=0  sun.gc.tlab.fills=0  sun.gc.tlab.gcWaste=0  sun.gc.tlab.maxFastWaste=0  sun.gc.tlab.maxFills=0  sun.gc.tlab.maxGcWaste=0  sun.gc.tlab.maxSlowAlloc=0  sun.gc.tlab.maxSlowWaste=0  sun.gc.tlab.slowAlloc=0  sun.gc.tlab.slowWaste=0  sun.management.JMXConnectorServer.0.authenticate="false"  sun.management.JMXConnectorServer.0.remoteAddress="service:jmx:rmi:///jndi/rmi://edu-cat02.lf.patterncat.com:8199/jmxrmi"  sun.management.JMXConnectorServer.0.ssl="false"  sun.management.JMXConnectorServer.0.sslNeedClientAuth="false"  sun.management.JMXConnectorServer.0.sslRegistry="false"  sun.management.JMXConnectorServer.address="service:jmx:rmi://127.0.0.1/stub/rO0ABXNyAC5qYXZheC5tYW5hZ2VtZW50LnJlbW90ZS5ybWkuUk1JU2VydmVySW1wbF9TdHViAAAAAAAAAAICAAB4cgAaamF2YS5ybWkuc2VydmVyLlJlbW90ZVN0dWLp/tzJi+FlGgIAAHhyABxqYXZhLnJtaS5zZXJ2ZXIuUmVtb3RlT2JqZWN002G0kQxhMx4DAAB4cHc3AAtVbmljYXN0UmVmMgAADDEwLjY0LjI4LjIwNwAAhbjWmVwaDwiNg3l3YeUAAAFNLZX68oACAHg="  sun.os.hrt.frequency=1000000  sun.os.hrt.ticks=24580753795  sun.perfdata.majorVersion=2  sun.perfdata.minorVersion=0  sun.perfdata.overflow=0  sun.perfdata.size=32768  sun.perfdata.timestamp=259316  sun.perfdata.used=17792  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"  sun.property.sun.boot.library.path="/usr/local/jdk1.7.0_21/jre/lib/amd64"  sun.rt._sync_ContendedLockAttempts=297851  sun.rt._sync_Deflations=438863  sun.rt._sync_EmptyNotifications=0  sun.rt._sync_FailedSpins=0  sun.rt._sync_FutileWakeups=349651  sun.rt._sync_Inflations=438971  sun.rt._sync_MonExtant=16256  sun.rt._sync_MonInCirculation=0  sun.rt._sync_MonScavenged=0  sun.rt._sync_Notifications=1580811  sun.rt._sync_Parks=1935145  sun.rt._sync_PrivateA=0  sun.rt._sync_PrivateB=0  sun.rt._sync_SlowEnter=0  sun.rt._sync_SlowExit=0  sun.rt._sync_SlowNotify=0  sun.rt._sync_SlowNotifyAll=0  sun.rt._sync_SuccessfulSpins=0  sun.rt.applicationTime=24559855809  sun.rt.createVmBeginTime=1430988913170  sun.rt.createVmEndTime=1430988913429  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)"  sun.rt.interruptedBeforeIO=0  sun.rt.interruptedDuringIO=0  sun.rt.javaCommand="org.eclipse.jetty.xml.XmlConfiguration /tmp/start4070493346048555702.properties /opt/educat/apps/conf/jetty8.xml"  sun.rt.jvmCapabilities="1000000000000000000000000000000000000000000000000000000000000000"  sun.rt.jvmVersion=387252225  sun.rt.safepointSyncTime=2333795  sun.rt.safepointTime=15955181  sun.rt.safepoints=18365  sun.rt.threadInterruptSignaled=0  sun.rt.vmInitDoneTime=1430988913232  sun.threads.vmOperationTime=9516621  sun.urlClassLoader.readClassBytesTime=958824201  sun.zip.zipFile.openTime=72163038  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

</div>

相关经验