Java5的新特性

• 泛型
• 枚舉
• 裝箱拆箱
• 變長參數(shù)
• 注解
• foreach循環(huán)
• 靜態(tài)導(dǎo)入
• 格式化
• 線程框架/數(shù)據(jù)結(jié)構(gòu)
• Arrays工具類/StringBuilder/instrument

1葱色、泛型

所謂類型擦除指的就是Java源碼中的范型信息只允許停留在編譯前期，而編譯后的字節(jié)碼文件中將不再保留任何的范型信息娘香。也就是說苍狰，范型信息在編譯時將會被全部刪除办龄，其中范型類型的類型參數(shù)則會被替換為Object類型，并在實(shí)際使用時強(qiáng)制轉(zhuǎn)換為指定的目標(biāo)數(shù)據(jù)類型淋昭。而C++中的模板則會在編譯時將模板類型中的類型參數(shù)根據(jù)所傳遞的指定數(shù)據(jù)類型生成相對應(yīng)的目標(biāo)代碼俐填。

Map<Integer, Integer> squares = new HashMap<Integer, Integer>();

• 通配符類型：避免unchecked警告，問號表示任何類型都可以接受

public void printList(List<?> list, PrintStream out) throws IOException {
    for (Iterator<?> i = list.iterator(); i.hasNext(); ) {
      out.println(i.next().toString());
    }
  }

• 限制類型

public static <A extends Number> double sum(Box<A> box1,Box<A> box2){
    double total = 0;
    for (Iterator<A> i = box1.contents.iterator(); i.hasNext(); ) {
      total = total + i.next().doubleValue();
    }
    for (Iterator<A> i = box2.contents.iterator(); i.hasNext(); ) {
      total = total + i.next().doubleValue();
    }
    return total;
  }

2翔忽、枚舉

• EnumMap

public void testEnumMap(PrintStream out) throws IOException {
    // Create a map with the key and a String message
    EnumMap<AntStatus, String> antMessages =
      new EnumMap<AntStatus, String>(AntStatus.class);
    // Initialize the map
    antMessages.put(AntStatus.INITIALIZING, "Initializing Ant...");
    antMessages.put(AntStatus.COMPILING,    "Compiling Java classes...");
    antMessages.put(AntStatus.COPYING,      "Copying files...");
    antMessages.put(AntStatus.JARRING,      "JARring up files...");
    antMessages.put(AntStatus.ZIPPING,      "ZIPping up files...");
    antMessages.put(AntStatus.DONE,         "Build complete.");
    antMessages.put(AntStatus.ERROR,        "Error occurred.");
    // Iterate and print messages
    for (AntStatus status : AntStatus.values() ) {
      out.println("For status " + status + ", message is: " +
                  antMessages.get(status));
    }
  }

• switch枚舉

public String getDescription() {
    switch(this) {
      case ROSEWOOD:      return "Rosewood back and sides";
      case MAHOGANY:      return "Mahogany back and sides";
      case ZIRICOTE:      return "Ziricote back and sides";
      case SPRUCE:        return "Sitka Spruce top";
      case CEDAR:         return "Wester Red Cedar top";
      case AB_ROSETTE:    return "Abalone rosette";
      case AB_TOP_BORDER: return "Abalone top border";
      case IL_DIAMONDS:   
        return "Diamonds and squares fretboard inlay";
      case IL_DOTS:
        return "Small dots fretboard inlay";
      default: return "Unknown feature";
    }
  }

3英融、Autoboxing與Unboxing

將primitive類型轉(zhuǎn)換成對應(yīng)的wrapper類型：Boolean、Byte歇式、Short驶悟、Character、Integer材失、Long痕鳍、Float、Double

public static void m1(Integer i){
        System.out.println("this is integer");
    }
    public static void m1(double d){
        System.out.println("this is double");
    }

m1(1)輸出的是double龙巨，方法匹配時線下兼容笼呆，不考慮boxing與unboxing。

4旨别、vararg

private String print(Object... values) {
    StringBuilder sb = new StringBuilder();
    for (Object o : values) {
      sb.append(o.toString())
        .append(" ");
    }
    return sb.toString();
  }

5诗赌、annotation

• Inherited表示該注解是否對類的子類繼承的方法等起作用

@Documented
@Inherited
@Retention(RetentionPolicy.RUNTIME)
public @interface InProgress { }

• 指定Target

@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE,
         ElementType.METHOD, 
         ElementType.CONSTRUCTOR, 
         ElementType.ANNOTATION_TYPE})
public @interface TODO { 
  String value();
}

• Target類型

public enum ElementType {
    /** Class, interface (including annotation type), or enum declaration */
    TYPE,
    /** Field declaration (includes enum constants) */
    FIELD,
    /** Method declaration */
    METHOD,
    /** Parameter declaration */
    PARAMETER,
    /** Constructor declaration */
    CONSTRUCTOR,
    /** Local variable declaration */
    LOCAL_VARIABLE,
    /** Annotation type declaration */
    ANNOTATION_TYPE,
    /** Package declaration */
    PACKAGE
}

• rentation表示annotation是否保留在編譯過的class文件中還是在運(yùn)行時可讀。

public enum RetentionPolicy {
    /**
     * Annotations are to be discarded by the compiler.
     */
    SOURCE,
    /**
     * Annotations are to be recorded in the class file by the compiler
     * but need not be retained by the VM at run time.  This is the default
     * behavior.
     */
    CLASS,
    /**
     * Annotations are to be recorded in the class file by the compiler and
     * retained by the VM at run time, so they may be read reflectively.
     *
     * @see java.lang.reflect.AnnotatedElement
     */
    RUNTIME
}

• 通過反射獲取元信息

public class ReflectionTester {
  public ReflectionTester() {
  }
  public void testAnnotationPresent(PrintStream out) throws IOException {
    Class c = Super.class;
    boolean inProgress = c.isAnnotationPresent(InProgress.class);
    if (inProgress) {
      out.println("Super is In Progress");
    } else {
      out.println("Super is not In Progress");
    }
  }
  public void testInheritedAnnotation(PrintStream out) throws IOException {
    Class c = Sub.class;
    boolean inProgress = c.isAnnotationPresent(InProgress.class);
    if (inProgress) {
      out.println("Sub is In Progress");
    } else {
      out.println("Sub is not In Progress");
    }
  }
  public void testGetAnnotation(PrintStream out) 
    throws IOException, NoSuchMethodException {
    Class c = AnnotationTester.class;
    AnnotatedElement element = c.getMethod("calculateInterest", 
                                  float.class, float.class);
    GroupTODO groupTodo = element.getAnnotation(GroupTODO.class);
    String assignedTo = groupTodo.assignedTo();
    out.println("TODO Item on Annotation Tester is assigned to: '" + 
        assignedTo + "'");
  }
  public void printAnnotations(AnnotatedElement e, PrintStream out)
    throws IOException {
    out.printf("Printing annotations for '%s'%n%n", e.toString());
    Annotation[] annotations = e.getAnnotations();
    for (Annotation a : annotations) {
      out.printf("    * Annotation '%s' found%n", 
        a.annotationType().getName());
    }
  }
  public static void main(String[] args) {
    try {
      ReflectionTester tester = new ReflectionTester();
      tester.testAnnotationPresent(System.out);
      tester.testInheritedAnnotation(System.out);
      tester.testGetAnnotation(System.out);
      Class c = AnnotationTester.class;
      AnnotatedElement element = c.getMethod("calculateInterest", 
                                    float.class, float.class);      
      tester.printAnnotations(element, System.out);
    } catch (Exception e) {
      e.printStackTrace();
    } 
  }
}

6昼榛、for/in

for/in循環(huán)辦不到的事情：
（1）遍歷同時獲取index
（2）集合逗號拼接時去掉最后一個
（3）遍歷的同時刪除元素

7境肾、靜態(tài)import

import static java.lang.System.err;
import static java.lang.System.out;
import java.io.IOException;
import java.io.PrintStream;
public class StaticImporter {
  public static void writeError(PrintStream err, String msg) 
    throws IOException {

    // Note that err in the parameter list overshadows the imported err
    err.println(msg); 
  }
  public static void main(String[] args) {
    if (args.length < 2) {
      err.println(
        "Incorrect usage: java com.oreilly.tiger.ch08 [arg1] [arg2]");
      return;
    }
    out.println("Good morning, " + args[0]);
    out.println("Have a " + args[1] + " day!");
    try {
      writeError(System.out, "Error occurred.");
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
}

8、格式化

/**
 * java.text.DateFormat
 * java.text.SimpleDateFormat
 * java.text.MessageFormat
 * java.text.NumberFormat
 * java.text.ChoiceFormat
 * java.text.DecimalFormat
 */
public class FormatTester {
    public static void printf() {
        //printf
        String filename = "this is a file";
        try {
            File file = new File(filename);
            FileReader fileReader = new FileReader(file);
            BufferedReader reader = new BufferedReader(fileReader);
            String line;
            int i = 1;
            while ((line = reader.readLine()) != null) {
                System.out.printf("Line %d: %s%n", i++, line);
            }
        } catch (Exception e) {
            System.err.printf("Unable to open file named '%s': %s",
                    filename, e.getMessage());
        }
    }
    public static void stringFormat() {
        // Format a string containing a date.
        Calendar c = new GregorianCalendar(1995, MAY, 23);
        String s = String.format("Duke's Birthday: %1$tm %1$te,%1$tY", c);
        // -> s == "Duke's Birthday: May 23, 1995"
        System.out.println(s);
    }
    public static void formatter() {
        StringBuilder sb = new StringBuilder();
        // Send all output to the Appendable object sb
        Formatter formatter = new Formatter(sb, Locale.US);
        // Explicit argument indices may be used to re-order output.
        formatter.format("%4$2s %3$2s %2$2s %1$2s", "a", "b", "c", "d");
        // -> " d  c  b  a"
        // Optional locale as the first argument can be used to get
        // locale-specific formatting of numbers.  The precision and width can be
        // given to round and align the value.
        formatter.format(Locale.FRANCE, "e = %+10.4f", Math.E);
        // -> "e =    +2,7183"
        // The '(' numeric flag may be used to format negative numbers with
        // parentheses rather than a minus sign.  Group separators are
        // automatically inserted.
        formatter.format("Amount gained or lost since last statement: $ %(,.2f",
                6217.58);
        // -> "Amount gained or lost since last statement: $ (6,217.58)"
    }
    public static void messageFormat() {
        String msg = "歡迎光臨胆屿，當(dāng)前（{0}）等待的業(yè)務(wù)受理的顧客有{1}位，請排號辦理業(yè)務(wù)偶宫！";
        MessageFormat mf = new MessageFormat(msg);
        String fmsg = mf.format(new Object[]{new Date(), 35});
        System.out.println(fmsg);
    }
    public static void dateFormat(){
        String str = "2010-1-10 17:39:21";
        SimpleDateFormat format = new SimpleDateFormat("yyyyMMddHHmmss");
        try {
            System.out.println(format.format(format.parse(str)));
        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    public static void main(String[] args) {
        formatter();
        stringFormat();
        messageFormat();
        dateFormat();
        printf();
    }
}

9非迹、threading

• uncaught exception

public class BubbleSortThread extends Thread {
  private int[] numbers;
  public BubbleSortThread(int[] numbers) {
    setName("Simple Thread");
    setUncaughtExceptionHandler(
      new SimpleThreadExceptionHandler());
    this.numbers = numbers;
  }
  public void run() {
    int index = numbers.length;
    boolean finished = false;
    while (!finished) {
      index--;
      finished = true;
      for (int i=0; i<index; i++) {
        // Create error condition
        if (numbers[i+1] < 0) {
          throw new IllegalArgumentException(
            "Cannot pass negative numbers into this thread!");
        }
        if (numbers[i] > numbers[i+1]) {
          // swap
          int temp = numbers[i];
          numbers[i] = numbers[i+1];
          numbers[i+1] = temp;
          finished = false;
        }
      }
    }    
  }
}
class SimpleThreadExceptionHandler implements
    Thread.UncaughtExceptionHandler {
  public void uncaughtException(Thread t, Throwable e) {
    System.err.printf("%s: %s at line %d of %s%n",
        t.getName(), 
        e.toString(),
        e.getStackTrace()[0].getLineNumber(),
        e.getStackTrace()[0].getFileName());
  }
}

• blocking queue

public class Producer extends Thread {
  private BlockingQueue q;
  private PrintStream out;
  public Producer(BlockingQueue q, PrintStream out) {
    setName("Producer");
    this.q = q;
    this.out = out;
  }
  public void run() {
    try {
      while (true) {
        q.put(produce());
      }
    } catch (InterruptedException e) {
      out.printf("%s interrupted: %s", getName(), e.getMessage());
    }
  }
  private String produce() {
    while (true) {
      double r = Math.random();
      // Only goes forward 1/10 of the time
      if ((r*100) < 10) {
        String s = String.format("Inserted at %tc", new Date());
        return s;
      }
    }
  }
}

• 線程池

著名的JUC類庫。

• 每次提交任務(wù)時纯趋，如果線程數(shù)還沒達(dá)到coreSize就創(chuàng)建新線程并綁定該任務(wù)憎兽。 所以第coreSize次提交任務(wù)后線程總數(shù)必達(dá)到coreSize，不會重用之前的空閑線程吵冒。
• 線程數(shù)達(dá)到coreSize后纯命，新增的任務(wù)就放到工作隊列里，而線程池里的線程則努力的使用take()從工作隊列里拉活來干痹栖。
• 如果隊列是個有界隊列亿汞，又如果線程池里的線程不能及時將任務(wù)取走，工作隊列可能會滿掉揪阿，插入任務(wù)就會失敗疗我，此時線程池就會緊急的再創(chuàng)建新的臨時線程來補(bǔ)救咆畏。
• 臨時線程使用poll(keepAliveTime，timeUnit)來從工作隊列拉活吴裤，如果時候到了仍然兩手空空沒拉到活旧找，表明它太閑了，就會被解雇掉麦牺。
• 如果core線程數(shù)＋臨時線程數(shù) >maxSize钮蛛，則不能再創(chuàng)建新的臨時線程了，轉(zhuǎn)頭執(zhí)行RejectExecutionHanlder剖膳。默認(rèn)的AbortPolicy拋RejectedExecutionException異常魏颓，其他選擇包括靜默放棄當(dāng)前任務(wù)(Discard)，放棄工作隊列里最老的任務(wù)(DisacardOldest)潮秘，或由主線程來直接執(zhí)行(CallerRuns)琼开，或你自己發(fā)揮想象力寫的一個。

10枕荞、其他

• Arrays

Arrays.sort(myArray);
Arrays.toString(myArray)
Arrays.binarySearch(myArray, 98)
Arrays.deepToString(ticTacToe)
Arrays.deepEquals(ticTacToe, ticTacToe3)

• Queue

避開集合的add/remove操作柜候，使用offer、poll操作（不拋異常）

Queue q = new LinkedList(); 采用它來實(shí)現(xiàn)queue

• Override返回類型

支持協(xié)變返回

• 單線程StringBuilder

線程不安全躏精，在單線程下替換string buffer提高性能

• java.lang.instrument

參考

• New Features and Enhancements J2SE 5.0

Java6新特性

• JSR223腳本引擎
• JSR199--Java Compiler API
• JSR269--Pluggable Annotation Processing API
• 支持JDBC4.0規(guī)范
• JAX-WS 2.0規(guī)范

1渣刷、JSR223腳本引擎

Scripting for the Java Platform

• 基本使用

public class BasicScripting {
    public void greet() throws ScriptException {
        ScriptEngineManager manager = new ScriptEngineManager();
        //支持通過名稱、文件擴(kuò)展名矗烛、MIMEtype查找
        ScriptEngine engine = manager.getEngineByName("JavaScript");
//        engine = manager.getEngineByExtension("js");
//        engine = manager.getEngineByMimeType("text/javascript");
        if (engine == null) {
            throw new RuntimeException("找不到JavaScript語言執(zhí)行引擎辅柴。");
        }
        engine.eval("println('Hello!');");
    }
    public static void main(String[] args) {
        try {
            new BasicScripting().greet();
        } catch (ScriptException ex) {
            Logger.getLogger(BasicScripting.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

• 綁定上下文

public class ScriptContextBindings extends JsScriptRunner {
    public void scriptContextBindings() throws ScriptException {
        ScriptEngine engine = getJavaScriptEngine();
        ScriptContext context = engine.getContext();
        Bindings bindings1 = engine.createBindings();
        bindings1.put("name", "Alex");
        context.setBindings(bindings1, ScriptContext.GLOBAL_SCOPE);
        Bindings bindings2 = engine.createBindings();
        bindings2.put("name", "Bob");
        context.setBindings(bindings2, ScriptContext.ENGINE_SCOPE);
        engine.eval("println(name);");
    }
    public void useScriptContextValues() throws ScriptException {
        ScriptEngine engine = getJavaScriptEngine();
        ScriptContext context = engine.getContext();
        Bindings bindings = context.getBindings(ScriptContext.ENGINE_SCOPE);
        bindings.put("name", "Alex");
        engine.eval("println(name);");
    }
    public void attributeInBindings() throws ScriptException {
        ScriptEngine engine = getJavaScriptEngine();
        ScriptContext context = engine.getContext();
        context.setAttribute("name", "Alex", ScriptContext.GLOBAL_SCOPE);
        engine.eval("println(name);");
    }
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) throws ScriptException {
        ScriptContextBindings scb = new ScriptContextBindings();
        scb.scriptContextBindings();
        scb.useScriptContextValues();
        scb.attributeInBindings();
    }
}

2、JSR199--Java Compiler API

public class JavaCompilerAPICompiler {
    public void compile(Path src, Path output) throws IOException {
        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
        try (StandardJavaFileManager fileManager = compiler.getStandardFileManager(null, null, null)) {
            Iterable<? extends JavaFileObject> compilationUnits = fileManager.getJavaFileObjects(src.toFile());
            Iterable<String> options = Arrays.asList("-d", output.toString());
            JavaCompiler.CompilationTask task = compiler.getTask(null, fileManager, null, options, null, compilationUnits);
            boolean result = task.call();
        }
    }
}

3瞭吃、JSR269--Pluggable Annotation Processing API

一部分是進(jìn)行注解處理的javax.annotation.processing碌嘀，另一部分是對程序的靜態(tài)結(jié)構(gòu)進(jìn)行建模的javax.lang.model

4、其他

• 支持JDBC4.0規(guī)范
• JAX-WS 2.0規(guī)范(包括JAXB 2.0)
• 輕量級HttpServer

參考

• Java 6 Features and Enhancements
• Java Platform, Standard Edition Differences between 5.0 fcs and 6 Beta

Java7新特性

• 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(guī)范)
• JSR203-More New I/O APIs for the Java Platform(新規(guī)范)
• JSR292與InvokeDynamic
• 支持JDBC4.1規(guī)范
• Path接口歪架、DirectoryStream股冗、Files、WatchService
• jcmd
• fork/join framework
• Java Mission Control

1和蚪、suppress異常(新語法)

/**
 * 記錄異常止状，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);
            }
        }
    }
}

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) {
        }
    }

3攒霹、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(guān)閉
 * 這是自動完成的怯疤。
 * @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();
        }
    }
}

實(shí)現(xiàn)AutoCloseable

/**
 * @created 2014-07-21
 */
public class CustomResource  implements AutoCloseable {
    public void close() throws Exception {
        System.out.println("進(jìn)行資源釋放。");
    }
    public void useCustomResource() throws Exception {
        try (CustomResource resource = new CustomResource())  {
            System.out.println("使用資源催束。");
        }
    }
    public static void main(String[] args) {
        try {
            new CustomResource().useCustomResource();
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }
}

4集峦、JSR341-Expression Language Specification(新規(guī)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(新規(guī)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();
    }
}

• 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(); //值為'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與InvokeDynamic

JSR 292: Supporting Dynamically Typed Languages on the JavaTM Platform少梁，支持在JVM上運(yùn)行動態(tài)類型語言洛口。在字節(jié)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(tǒng)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凯沪，MethodHandle
     * invoke virtual 動態(tài)綁定后調(diào)用 obj.xxx
     * invoke special 靜態(tài)綁定后調(diào)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_);
        }
    }
}

• 調(diào)用

public class ThreadPoolMain {
    /**
     * 如果被繼承第焰，還能在靜態(tài)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);
    }
}

7、支持JDBC4.1規(guī)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(wù)：" + r.getClass());
            super.beforeExecute(t, r);
        }
    }
    public static void main(String[] args) {
        AbortConnection ca = new AbortConnection();
        try {
            ca.abortConnection();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

• 自動關(guān)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();
        }
    }
}

• 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();
        }
    }
}

8妨马、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挺举、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烘跺、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湘纵、jcmd utility

jcmd是為了替代jps出現(xiàn)了，包含了jps的大部分功能并新增了一些新的功能滤淳。

• jcmd -l

列出所有的Java虛擬機(jī)梧喷，針對每一個虛擬機(jī)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(shù)

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 導(dǎo)出堆信息
• jcmd pid GC.class_histogram查看系統(tǒng)中類的統(tǒng)計信息
• jcmd pid VM.system_properties查看系統(tǒng)屬性內(nèi)容
• jcmd pid Thread.print 打印線程棧
• jcmd pid VM.uptime 查看虛擬機(jī)啟動時間
• jcmd pid PerfCounter.print 查看性能統(tǒng)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/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脖咐、fork/join

Java7提供的一個用于并行執(zhí)行任務(wù)的框架铺敌，是一個把大任務(wù)分割成若干個小任務(wù)，最終匯總每個小任務(wù)結(jié)果后得到大任務(wù)結(jié)果的框架屁擅。

14偿凭、Java Mission Control

在JDK7u40里頭提供了Java Mission Control，這個是從JRockit虛擬機(jī)里頭遷移過來的類似JVisualVm的東東派歌。

15弯囊、其他

• Binary Literals支持
• Numeric Literals的下劃線支持
• Strings in switch Statements

參考

• Java SE 7 Features and Enhancements

文章太長了，此平臺不支持了胶果，另開一篇文章：Java8到Java12新特性見這里 http://www.reibang.com/p/e5fba5376371