Java 7, 8 & 9 - Moving the language forward

Java 7, 8 & 9 - Moving the language forward

• 1.
  7, 8 &9 Moving the language forward by Mario Fusco Red Hat – Senior Software Engineer mario.fusco@gmail.com twitter: @mariofusco
• 2.
  New in Java7 – Released in July 2011 • JSR 292: Support for dynamically-typed languages (InvokeDynamic) • JSR 334: Small language enhancements (Project Coin) • JSR 166y: Concurrency and collection updates (Fork/Join framework) • JSR 203: More new I/O APIs for the Java platform (NIO.2)
• 3.
  Switch on Strings switch(dayOfWeek){ case "Monday" : System.out.println("Start of week"); break; .... case "Sunday" : System.out.println("Hurrey.. its weekend"); break; }
• 4.
  Improved Exception handling publicvoid printFileContent(String fileName) throws IOException { Configuration cfg = null; try { String fileText = getFile(fileName); //...code to print content } catch (FileNotFoundException | FileLockInterruptionException e1) { System.err.println("error while opening file"); throw e1; } catch (ParseException e2) { System.err.println("Error processing file"); } }
• 5.
  Try with resources try( FileOutputStream fos = new FileOutputStream(file); InputStream is = url.openStream() ) { byte[] buf = new byte[4096]; int len; while ((len = is.read(buf)) > 0) { fos.write(buf, 0, len); } }
• 6.
  Diamond Operator Map<Person, List<Address>> Underscores in numeric literals static final int ONE_MILLION = 1_000_000
• 7.
  Fork/Join Framework public classFileSizeFinder extends RecursiveTask<Long> { private final File file; public FileSizeFinder(File theFile) { file = theFile; } @Override public Long compute() { long size = 0; if (file.isFile()) return file.length(); File[] children = file.listFiles(); if (children == null) return size; List<ForkJoinTask<Long>> tasks = new ArrayList<>(); for (File child : children) { if (child.isFile()) size += child.length(); else tasks.add(new FileSizeFinder(child)); } for (ForkJoinTask<Long> task : invokeAll(tasks)) size += task.join(); return size; } } long total = new ForkJoinPool().invoke(new FileSizeFinder(new File(rootName)));
• 8.
  Coming in Java8 – Early (hopefully) 2013 • JSR 335: Project Lambda • JSR TBD: Language support for collections • JSR 308: Annotations on Java types • JSR 310: Date and Time API (from JodaTime) • JSR 294: Language and VM support for modular programming • JSR TBD: Project Jigsaw (Modularization)
• 9.
  Project Lambda -Background public interface Comparator<T> { Functional int compare(T o1, T o2); } Interface Collections.sort(strings, new Comparator<String>() { public int compare(String s1, String s2) { return s1.compareToIgnoreCase(s2); } }); • Bulky syntax • Confusion surrounding the meaning of names and this • Inability to capture non-final local variables • Inability to abstract over control flow
• 10.
  Lambda Expressions Collections.sort(strings, (s1,s2) -> s1.compareToIgnoreCase(s2)); Target typing Comparator<String> c = (s1, s2) -> s1.compareToIgnoreCase(s2); Method reference Collections.sort(strings, String::compareToIgnoreCase);
• 11.
  Lambda support forcollections double maxScore = 0; for (Student s : students) { if (s.gradYear == 2011) { maxScore = Math.max(maxScore, s.score); } } double maxScore = students.parallel() .filter(s -> s.gradYear == 2011) .map(s -> s.score) .reduce(0, Math::max);
• 12.
  Default methods interface Iterator<E>{ boolean hasNext(); E next(); void remove(); void skip(int i) default { for (; i > 0 && hasNext(); i--) next(); } boolean filter default Iterables::filter }
• 13.
  What to expectfrom Java 9