Java7 New Features and Code Examples

Java 7
New Features & Code Examples
Naresh Chintalcheru

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

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”};

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) {}
}

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

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

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

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;
}

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

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

String in Switch Statement
Finally ☺ ☺ ☺
String day;

switch (day) {
case "Monday":
break;
case "Tuesday":
case "Sunday":
typeOfDay = "Weekend";
break;
default:
throw new IllegalArgumentException("Invalid");
}

.

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<>();

.

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
.

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
.

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 {
try (Scanner scanner = new Scanner(path, ENCODING.name())){
while (scanner.hasNextLine()){
log(scanner.nextLine());
//Read String Line
}
}}

.

Path & Files To Write
final static Charset ENCODING = StandardCharsets.UTF_8;

void writeFile(List<String> aLines, String aFileName) throws IOException {
Files.write(path, aLines, ENCODING); //Write using List
}
void writeFile(String aFileName, List<String> aLines) throws IOException {
try (BufferedWriter writer = Files.newBufferedWriter(path, ENCODING)){
for(String line : aLines){
writer.write(line);
//Write String line
writer.newLine();
}
}}.

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);

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.

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.

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.

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

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();

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

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.

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

.

Java 7 Performance
Improved String Performance
Improved Array Performance
Security Enhancements
Support for Non-Java Languages - invokedynamic

References
http://www.oracle.com/technetwork/java/javase/jdk7-relnotes-418459.html
http://radar.oreilly.com/2011/09/java7-features.html
http://www.slideshare.net/boulderjug/55-things-in-java-7
http://jaxenter.com/java-7-the-top-8-features-37156.html
http://stackoverflow.com/questions/2606620/what-are-the-new-features-in-java-7
http://tamanmohamed.blogspot.com/2012/06/jdk7-part-1-java-7-dolphin-newfeatures.html
http://tech.puredanger.com/java7/

Java7 New Features and Code Examples

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