Java7 New Features and Code Examples
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This document summarizes new features in Java 7, including underscores in numeric literals to improve readability, try-with-resource for automatic resource management, multi-catch exceptions, and various improvements to I/O, generics, and garbage collection. Key areas covered are numeric literals, collection initialization, try-with-resource blocks, multi-catch exceptions, final rethrow, strings in switch statements, generic instances, NIO2 file APIs, file change notifications, asynchronous I/O, URLClassLoader closing, JDBC row sets, varargs, the G1 garbage collector, and improved performance.
![URLClassLoader Closing
URL url = new URL("file:foo.jar");
URLClassLoader loader = new URLClassLoader (new URL[] {url});
Class cl = Class.forName ("Foo", true, loader);
Runnable foo = (Runnable) cl.newInstance();
foo.run();
loader.close ();
// foo.jar gets updated somehow
loader = new URLClassLoader (new URL[] {url});
cl = Class.forName ("Foo", true, loader);
foo = (Runnable) cl.newInstance();
// run the new implementation of Foo
foo.run();
Eliminates Server restarts](https://image.slidesharecdn.com/java7features-140206081446-phpapp01/85/Java7-New-Features-and-Code-Examples-21-320.jpg)
![Varargs
public class VarArgsJavav6 {
public static void main(String[] args) {
vaMethod("a", "b", "c");
}
public void vaMethod(String... args) {
for(String s : args)
System.out.println(s);
}
}
Automatically treats Method parameter as an Array](https://image.slidesharecdn.com/java7features-140206081446-phpapp01/85/Java7-New-Features-and-Code-Examples-23-320.jpg)
Java7 New Features and Code Examples
- 1. Java 7 New Features & Code Examples Naresh Chintalcheru
- 2. Numeric Literals with Underscores int thousand = 1_000; int million = 1_000_000; //1000000 (one million) double d1 = 1000_000_.0d long a1 = 0b1000_1010_0010_1101_1010_0001_0100_0101L; Imagine counting tens of zero’s ?. No need to strain eyes or manual errors with Underscores
- 3. Bracket Notation for Collection Old-Way Collection<String> c = new ArrayList(); c.add(“one”); c.add(“two”); c.add(“ten”); New-Way Collection<String> c = new ArrayList {“one”, “two”, “ten”};
- 4. try-with-resource Old-Way BufferedReader br = null; try { br = new BufferedReader(new FileReader(path)); return br.readLine(); }catch(IOException ioEx) {} finally { try{ br.close(); }catch(IOException ioEx) {} }
- 5. try-with-resource • The File, JDBC, MQ, LDAP & Mail resource connections will be opened & closed • The finally block is used to make sure the resources are closed • Have another try-catch for closing the resources
- 6. try-with-resource New-Way try (BufferedReader br = new BufferedReader(new FileReader(path)); BufferedWriter bw = new BufferedWriter(new FileWriter(path)); ){ //File code } catch(IOException ioEx) { } With Java7 try-with-resource the resources BufferedReader & BufferedWriter implements java.lang. AutoCloseable and will be closed automatically
- 7. try-with-resource New-Way try (Statement stmt = con.createStatement()) { ResultSet rs = stmt.executeQuery(query); while (rs.next()) String coffeeName = rs.getString("Name”); } catch (SQLException e) { } With Java7 try-with-resource the resource javax.sql. Statement implements java.lang.AutoCloseable and will be closed automatically
- 8. Multi-Catch Old-Way try { //statements } catch (ExceptionOne ex) { logger.error(ex); throw ex; } catch (ExceptionTwo ex) { logger.error(ex); throw ex; } catch (ExceptionThree ex) { logger.error(ex); throw ex; }
- 9. Multi-Catch New-Way try { //statements } catch (ExceptionOne | ExceptionTwo | ExceptionThree ex) { logger.error(ex); throw ex; } Clean code with multiple exceptions in one Catch block
- 10. Final Rethrow void process() throws IOException, SQLException try { //statements } catch (final throw ex; } Throwable ex) { New precise rethrow feature which lets catch and throw the base exception while still throwing the precise exception from the calling method
- 11. String in Switch Statement Finally ☺ ☺ ☺ String day; switch (day) { case "Monday": break; case "Tuesday": case "Sunday": typeOfDay = "Weekend"; break; default: throw new IllegalArgumentException("Invalid"); } .
- 12. Simple Generic Instance Old-Way List<String> strings = new ArrayList<String>(); Map<String, List<String>> myMap = new HashMap<String, List<String>>(); New-Way (Simple) List<String> strings = new ArrayList<>(); Map<String, List<String>> myMap = new HashMap<>(); .
- 13. Java.nio.file* (NIO2) java.nio.file.Files java.nio.file.Path java.nio.file.Paths Paths and Path - File locations/names Files - Operations on file content FileSystem – provides file services File.toPath() method, Lets older code interact with the new java.nio API .
- 14. Create File Symbolic Link java.nio.file.Files.createSymbolicLink() createSymbolicLink() – creates a symbolic link, if supported by the file system public static Path createSymbolicLink(Path link, Path target, FileAttribute<?>... attrs) throws IOException .
- 15. Path, Files & Scanner final static Charset ENCODING = StandardCharsets.UTF_8; List<String> readFile(String aFileName) throws IOException { Path path = Paths.get(aFileName); return Files.readAllLines(path, ENCODING); //Read List } void readFile(String aFileName) throws IOException { Path path = Paths.get(aFileName); try (Scanner scanner = new Scanner(path, ENCODING.name())){ while (scanner.hasNextLine()){ log(scanner.nextLine()); //Read String Line } }} .
- 16. Path & Files To Write final static Charset ENCODING = StandardCharsets.UTF_8; void writeFile(List<String> aLines, String aFileName) throws IOException { Path path = Paths.get(aFileName); Files.write(path, aLines, ENCODING); //Write using List } void writeFile(String aFileName, List<String> aLines) throws IOException { Path path = Paths.get(aFileName); try (BufferedWriter writer = Files.newBufferedWriter(path, ENCODING)){ for(String line : aLines){ writer.write(line); //Write String line writer.newLine(); } }}.
- 17. File Change Notifications File Change Notifications with WatchService APIs private void watch() { Path path = Paths.get("C:Temptemp"); try { watchService = FileSystems.getDefault().newWatchService(); path.register(watchService, ENTRY_CREATE, ENTRY_DELETE, } catch (IOException e) { System.out.println("IOException"+ e.getMessage()); } } ENTRY_MODIFY);
- 18. Streaming & Channel-based I/O • A stream is a contiguous sequence of data. Stream IO acts on a single character at a time, while channel IO works with a buffer for each operation. • These are supported by the Files class and Buffered IO is usually more efficient to be used in reading and writing data. • The java.nio.channels package's ByteChannel interface is a channel that can read and write bytes. • The SeekableByteChannel interface extends the ByteChannel interface to maintain a position within the channel. The position can be changed using seek type random IO operations.
- 19. Asynchronous Channel-based I/O Support for Asynchronous channel-based I/O functionality • AsynchronousFileChannel class is used for file manipulation operations that need to be performed in an asynchronous manner, the methods supporting the File write and read operations. • AsynchronousChannelGroup class provides a means of grouping asynchronous channels together in order to share resources. • Java.nio.file package's SecureDirectoryStream class provides support for more secure access to directories. However, the underlying operating system must provide local support for this class.
- 20. URLClassLoader Closing The URLClassLoader.close() method eliminates the problem of supporting updated implementations of the classes and resources loaded from a particular codebase, and in particular from JAR files.
- 21. URLClassLoader Closing URL url = new URL("file:foo.jar"); URLClassLoader loader = new URLClassLoader (new URL[] {url}); Class cl = Class.forName ("Foo", true, loader); Runnable foo = (Runnable) cl.newInstance(); foo.run(); loader.close (); // foo.jar gets updated somehow loader = new URLClassLoader (new URL[] {url}); cl = Class.forName ("Foo", true, loader); foo = (Runnable) cl.newInstance(); // run the new implementation of Foo foo.run(); Eliminates Server restarts
- 22. JDBCRowSet The RowSetFactory interface and the RowSetProvider class, which enable you to create all types of row sets supported by the JDBC driver. RowSetFactory myRowSetFactory = RowSetProvider.newFactory(); JdbcRowSet jdbcRs = myRowSetFactory.createJdbcRowSet(); jdbcRs.setUrl("jdbc:driver:myAttribute"); jdbcRs.setUsername(username); jdbcRs.setPassword(password); jdbcRs.setCommand("select * from Emp"); jdbcRs.execute(); jdbcRs.moveToInsertRow(); jdbcRs.updateInt(“AGE", 0); jdbcRs.insertRow(); jdbcRs.last(); jdbcRs.deleteRow();
- 23. Varargs public class VarArgsJavav6 { public static void main(String[] args) { vaMethod("a", "b", "c"); } public void vaMethod(String... args) { for(String s : args) System.out.println(s); } } Automatically treats Method parameter as an Array
- 24. JVM G1 Garbage Collector • The Garbage-First (G1) garbage collector achieves high performance and pause time goals through several techniques • The G1 collector is a server-style garbage collector, targeted for multi-processor machines with large memories • Meets garbage collection (GC) pause time goals with high probability, while achieving high throughput.
- 25. Dynamic Language Support • Java is a static typed language to make it little bit more dynamic (long way to go) similar to dynamic typed languages like Ruby, Python & Clojure the new package java.lang. invoke is introduced • A new package java.lang.invoke includes classes MethodHandle, CallSite and others, has been created to extend the support of dynamic languages .
- 26. Java 7 Performance Improved String Performance Improved Array Performance Security Enhancements Support for Non-Java Languages - invokedynamic
- 28. Thank You