Java7的新特性

codecraft
Java语言特性系列

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。
     * @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

    /**
     * @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。

  • org.eclipse.jetty.xml.XmlConfiguration /tmp/start4070493346048555702.properties /opt/educat/apps/conf/jetty8.xml
  • sun.tools.jcmd.JCmd -l
  • 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/codecraft/logs/catapp.vmerr.log.201505071655 
    -XX:+HeapDumpOnOutOfMemoryError 
    -XX:HeapDumpPath=/var/codecraft/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/codecraft/logs/catapp.gc.log.201505071655 -XX:ErrorFile=/var/codecraft/logs/catapp.vmerr.log.201505071655 -XX:HeapDumpPath=/var/codecraft/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/codecraft/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.codecraft.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

  • Java SE 7 Features and Enhancements
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当一个代码的工匠回首往事时,不因虚度年华而悔恨,也不因碌碌无为而羞愧,这样,当他老的时候,可以很...

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