Java7的新特性

RicMcReynol 8年前發布 | 35K 次閱讀 Java7 JRE Java開發

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

Java語言特性系列

</div>

序

本文主要講Java7的新特性，相對于Java6而言，Java7增加了一些重要的特性，比如NIO2，不像Java6那么雞肋，也算是一個重要的版本。

特性列表

  • suppress異常( 新語法 )

  • 捕獲多個異常(新語法)

  • try-with-resources(新語法)

  • JSR341-Expression Language Specification(新規范)

  • JSR203-More New I/O APIs for the Java Platform(新規范)

  • JSR292與InvokeDynamic

  • 支持JDBC4.1規范

  • Path接口、DirectoryStream、Files、WatchService

  • jcmd

  • fork/join framework

  • Java Mission Control

1、suppress異常( 新語法 ) 

/**


    

  • 記錄異常，不被淹沒
    • 

  • 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);
     }
 }

    

    }
}</pre>
    

     2、捕獲多個異常( 新語法 ) 
    public void handle() {
    


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

    

    }</pre>
    

     3、try-with-resources( 新語法 ) 
    /**
    

    • 

  • try-with-resource
    • 

  • 不需要使用finally來保證打開的流被正確關閉
    • 

  • 這是自動完成的。
    • 

  • @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();
 }

    

    }
}</pre>
    

    實現AutoCloseable
    /**
    

    • 

  • @author patterncat
    • 

  • @created 2014-07-21
*/
public class CustomResource  implements AutoCloseable {
 public void close() throws Exception {
    


     System.out.println("進行資源釋放。");

    

    }
 public void useCustomResource() throws Exception {
    


     try (CustomResource resource = new CustomResource())  {
     System.out.println("使用資源。");
 }

    

    }
 public static void main(String[] args) {
    


     try {
     new CustomResource().useCustomResource();
 } catch (Exception ex) {
     ex.printStackTrace();
 }

    

    }
}</pre>
    

     4、JSR341-Expression Language Specification( 新規范 ) 
    public static void main(String[] args){
    


     ELProcessor el = new ELProcessor();
 assert (el.eval("Math.random()") instanceof Double);

    

    }</pre>
    

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

    •  
      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); //值為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(); //值為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();
}
}</pre> 

         
      •  
        filechannel
        

        • 

      

      </ul>
      

      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(); //值為'B'

      

      }
 /**
      

        

      • @param args the command line arguments
*/
public static void main(String[] args) throws IOException {
 FileChannelUsage fcu = new FileChannelUsage();
 fcu.openAndWrite();
 fcu.readWriteAbsolute();
}
}</pre> 
        6、JSR292與InvokeDynamic
        • 

      

      JSR 292: Supporting Dynamically Typed Languages on the JavaTM Platform，支持在JVM上運行動態類型語言。在字節碼層面支持了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);

      

      }
 /**
      

        

      • 使用傳統的反射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;
}
/**
        • 

      • 使用代理類
        • 

      • @return
*/
public CancelProxy makeProxy() {
 return new CancelProxy();
}
/**
        • 

      • 使用Java7的新api，MethodHandle
        • 

      • invoke virtual 動態綁定后調用 obj.xxx
        • 

      • invoke special 靜態綁定后調用 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_);

        
 }
}
}</pre> 

           
        •  
          調用
          

          • 

        

        </ul>
        

        public class ThreadPoolMain {
 /**
        

          

        • 如果被繼承，還能在靜態上下文尋找正確的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);
}
}</pre> 
          7、支持JDBC4.1規范
          • 

        

           

        •  
          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("清理任務：" + r.getClass());
     super.beforeExecute(t, r);
 }

        

        }
 public static void main(String[] args) {
        


         AbortConnection ca = new AbortConnection();
 try {
     ca.abortConnection();
 } catch (SQLException e) {
     e.printStackTrace();
 }

        

        }
}</pre>
        

           

        •  
          自動關閉
          

          • 


        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();
 }

        

        }
}</pre>
        

           

        •  
          自動映射
          

          • 


        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();
 }

        

        }
}</pre>
        

         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();
}
}</pre> 
          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();
}
}</pre> 
          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();
}
}</pre> 
          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();
}
}</pre> 
          12、jcmd utility
          • 

        

        jcmd是為了替代jps出現了，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虛擬機，針對每一個虛擬機可以使用help列出它們支持的命令。 
          

          • 


        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查看啟動參數
          

          • 


        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 導出堆信息
          

          • 


        •  
          jcmd pid GC.class_histogram查看系統中類的統計信息
          

          • 


        •  
          jcmd pid VM.system_properties查看系統屬性內容
          

          • 


        •  
          jcmd pid Thread.print 打印線程棧
          

          • 


        •  
          jcmd pid VM.uptime 查看虛擬機啟動時間
          

          • 


        •  
          jcmd pid PerfCounter.print 查看性能統計
          

          • 


        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提供的一個用于并行執行任務的框架，是一個把大任務分割成若干個小任務，最終匯總每個小任務結果后得到大任務結果的框架。
        14、Java Mission Control
        在JDK7u40里頭提供了Java Mission Control，這個是從JRockit虛擬機里頭遷移過來的類似JVisualVm的東東。
        15、其他
           

        •  
          Binary Literals支持
          

          • 


        •  
          Numeric Literals的下劃線支持
          

          • 


        •  
          Strings in switch Statements
          

          • 


        參考
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