Java7的新特性

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    Java语言特性系列

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    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
    java
    codecraft
    11.9k 声望2k 粉丝

    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，可以很自豪告诉世人，我曾经将代码注入生命去打造互联网的浪潮之巅，那是个很疯狂的时代，我在一波波的浪潮上留下...

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