Java7开发代号是Dolphin(海豚),于2011-07-28发行.
评价：不温不火
public String generate(String name, String gender) { String title = ""; switch (gender) { case "男": title = name + " 先生"; break; case "女": title = name + " 女士"; break; default: title = name; } return title; }编译器在编译时先做处理：
①case仅仅有一种情况。直接转成if。
②假设仅仅有一个case和default，则直接转换为if…else…。
③有多个case。先将String转换为hashCode，然后相应的进行处理，JavaCode在底层兼容Java7曾经版本号。
Java7前支持十进制（123）、八进制（0123）、十六进制（0X12AB）
Java7添加二进制表示（0B11110001、0b11110001）
数字中可加入分隔符
Java7中支持在数字量中间添加’_'作为分隔符。更直观，如（12_123_456）。下划线仅仅能在数字中间。编译时编译器自己主动删除数字中的下划线。
int one_million = 1_000_000;catch子句能够同一时候捕获多个异常
public void testSequence() { try { Integer.parseInt("Hello"); } catch (NumberFormatException | RuntimeException e) { //使用'|'切割，多个类型，一个对象e } } try-with-resources语句
Java7之前须要在finally中关闭socket、文件、数据库连接等资源；
Java7中在try语句中申请资源，实现资源的自己主动释放（资源类必须实现java.lang.AutoCloseable接口，一般的文件、数据库连接等均已实现该接口，close方法将被自己主动调用）。
public void read(String filename) throws IOException { try (BufferedReader reader = new BufferedReader(new FileReader(filename))) { StringBuilder builder = new StringBuilder(); String line = null; while((line=reader.readLine())!=null){ builder.append(line); builder.append(String.format("%n")); } return builder.toString(); } } 之前
Map<String, List<String>> map = new HashMap<String, List<String>>(); Java7之后可以简单的这么写
Map<String, List<String>> anagrams = new HashMap<>();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(); }}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(); }}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。
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_); } }}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); }}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(); }}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(); }}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(); }}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(); }}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。
该框架为Java8的并行流打下了坚实的基础
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