从Java5到Java12每个版本的新特性（1）
2018-12-02 本文已影响2190人
4ea0af17fd67
Java5的新特性
- 泛型
- 枚举
- 装箱拆箱
- 变长参数
- 注解
- foreach循环
- 静态导入
- 格式化
- 线程框架/数据结构
- Arrays工具类/StringBuilder/instrument
1、泛型
所谓类型擦除指的就是Java源码中的范型信息只允许停留在编译前期，而编译后的字节码文件中将不再保留任何的范型信息。也就是说，范型信息在编译时将会被全部删除，其中范型类型的类型参数则会被替换为Object类型，并在实际使用时强制转换为指定的目标数据类型。而C++中的模板则会在编译时将模板类型中的类型参数根据所传递的指定数据类型生成相对应的目标代码。
Map<Integer, Integer> squares = new HashMap<Integer, Integer>();
- 通配符类型：避免unchecked警告，问号表示任何类型都可以接受
public void printList(List<?> list, PrintStream out) throws IOException {
for (Iterator<?> i = list.iterator(); i.hasNext(); ) {
out.println(i.next().toString());
}
}
- 限制类型
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、枚举
- 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枚举
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、Autoboxing与Unboxing
将primitive类型转换成对应的wrapper类型：Boolean、Byte、Short、Character、Integer、Long、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)输出的是double，方法匹配时线下兼容，不考虑boxing与unboxing。
4、vararg
private String print(Object... values) {
StringBuilder sb = new StringBuilder();
for (Object o : values) {
sb.append(o.toString())
.append(" ");
}
return sb.toString();
}
5、annotation
- Inherited表示该注解是否对类的子类继承的方法等起作用
@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类型
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是否保留在编译过的class文件中还是在运行时可读。
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
}
- 通过反射获取元信息
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、for/in
for/in循环办不到的事情：
（1）遍历同时获取index
（2）集合逗号拼接时去掉最后一个
（3）遍历的同时删除元素
7、静态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 = "欢迎光临，当前（{0}）等待的业务受理的顾客有{1}位，请排号办理业务！";
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、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;
}
}
}
}
- 线程池
著名的JUC类库。
- 每次提交任务时，如果线程数还没达到coreSize就创建新线程并绑定该任务。 所以第coreSize次提交任务后线程总数必达到coreSize，不会重用之前的空闲线程。
- 线程数达到coreSize后，新增的任务就放到工作队列里，而线程池里的线程则努力的使用take()从工作队列里拉活来干。
- 如果队列是个有界队列，又如果线程池里的线程不能及时将任务取走，工作队列可能会满掉，插入任务就会失败，此时线程池就会紧急的再创建新的临时线程来补救。
- 临时线程使用poll(keepAliveTime，timeUnit)来从工作队列拉活，如果时候到了仍然两手空空没拉到活，表明它太闲了，就会被解雇掉。
- 如果core线程数＋临时线程数 >maxSize，则不能再创建新的临时线程了，转头执行RejectExecutionHanlder。默认的AbortPolicy抛RejectedExecutionException异常，其他选择包括静默放弃当前任务(Discard)，放弃工作队列里最老的任务(DisacardOldest)，或由主线程来直接执行(CallerRuns)，或你自己发挥想象力写的一个。
10、其他
- Arrays
Arrays.sort(myArray);
Arrays.toString(myArray)
Arrays.binarySearch(myArray, 98)
Arrays.deepToString(ticTacToe)
Arrays.deepEquals(ticTacToe, ticTacToe3)
- Queue
避开集合的add/remove操作，使用offer、poll操作（不抛异常）
Queue q = new LinkedList(); 采用它来实现queue
- Override返回类型
支持协变返回
- 单线程StringBuilder
线程不安全，在单线程下替换string buffer提高性能
- java.lang.instrument
参考
Java6新特性
- JSR223脚本引擎
- JSR199--Java Compiler API
- JSR269--Pluggable Annotation Processing API
- 支持JDBC4.0规范
- JAX-WS 2.0规范
1、JSR223脚本引擎
Scripting for the Java Platform
- 基本使用
public class BasicScripting {
public void greet() throws ScriptException {
ScriptEngineManager manager = new ScriptEngineManager();
//支持通过名称、文件扩展名、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语言执行引擎。");
}
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);
}
}
}
- 绑定上下文
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、JSR269--Pluggable Annotation Processing API
一部分是进行注解处理的javax.annotation.processing，另一部分是对程序的静态结构进行建模的javax.lang.model
4、其他
- 支持JDBC4.0规范
- JAX-WS 2.0规范(
包括JAXB 2.0) - 轻量级HttpServer
参考
- Java 6 Features and Enhancements
- Java Platform, Standard Edition Differences between 5.0 fcs and 6 Beta
Java7新特性
- 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。
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
文章太长了，此平台不支持了，另开一篇文章：Java8到Java12新特性见这里 https://www.jianshu.com/p/e5fba5376371
