The document summarizes new features in Java 7-8 including lambda expressions, switch on strings, try-with-resources, and the fork/join framework. Java 8 will focus on lambda expressions to provide functional programming capabilities and default methods to allow interfaces to have default implementations without breaking existing implementations. Java 9 may include additional modularization support.

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 Java 7 – 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
public void 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 class FileSizeFinder 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 Java 8 – 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 for collections
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 expect from Java 9