Java7 Features

Java SE 7 {finally}

2011-08-18
Andreas Enbohm

© 2004 Capgemini - All rights reserved

Java SE 7

A evolutionary evolement of Java
6 years since last update
Some things left out, will briefly discuss this at the end
Oracle really pushing Java forward
- a lot political problems with Sun made Java 7 postphoned
several times
Java still growing (1.42%), #1 most used language according to
TIOBE with 19.4% (Aug 2011)
My top 10 new features (not ordered in any way )

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15 januari 2014

Java SE 7 – Language Changes

Number 1:
Before :

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Try-with-resources Statement (or ARM-blocks)

static String readFirstLineFromFileWithFinallyBlock(String path)
throws IOException {
BufferedReader br = new BufferedReader(new FileReader(path));
try {
return br.readLine();
} finally {
if (br != null) {
try {
br.close();
} catch (IOException ignore){
//do nothing
}
}
}
}


Number 1:

Try-with-resources Statement (or ARM-blocks)

With Java 7:
static String readFirstLineFromFile(String path) throws IOException {
try (BufferedReader br = new BufferedReader(new FileReader(path))) {
return br.readLine();
}
}

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Number 1 - NOTE:
The try-with-resources statement is a try statement that declares one or more resources. A
resource is as an object that must be closed after the program is finished with it.
The try-with-resources statement ensures that each resource is closed at the end of the
statement.
Any object that implements java.lang.AutoCloseable, which includes all objects which
implement java.io.Closeable, can be used as a resource.

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Number 2:

Strings in switch Statements

public String getTypeOfDayWithSwitchStatement(String dayOfWeekArg) {
String typeOfDay;
switch (dayOfWeekArg) {
case "Monday":
typeOfDay = "Start of work week";
break;
case "Tuesday":
case "Wednesday":
case "Thursday":
typeOfDay = "Midweek";
break;
case "Friday":
typeOfDay = "End of work week";
break;
case "Saturday":
case "Sunday":
typeOfDay = "Weekend";
break;
default:
throw new IllegalArgumentException("Invalid day of the week: " + dayOfWeekArg);
}
return typeOfDay;
}
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Number 2 - NOTE:
The Java compiler generates generally more efficient bytecode from switch statements that
use String objects than from chained if-then-else statements.

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Number 3:
Before :

Catching Multiple Exception Types

try {
…
} catch (IOException ex) {
logger.log(ex);
throw ex;
} catch (SQLException ex) {
logger.log(ex);
throw ex;
}

Difficult to eliminate code duplication due to different exceptions!
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Number 3:

Catching Multiple Exception Types

With Java 7 :
try {
…
} catch (IOException|SQLException ex) {
logger.log(ex);
throw ex;
}

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Number 3 - NOTE: Catching Multiple Exception Types
Bytecode generated by compiling a catch block that handles multiple
exception types will be smaller (and thus superior) than
compiling many catch blocks that handle only one exception type
each.

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Number 4:

Type Inference for Generic Instance Creation

Before:
Map<String, List<String>> myMap = new HashMap<String, List<String>>();

How many times have you sworn about this duplicated code? 

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Number 4:

Type Inference for Generic Instance Creation

With Java 7:
Map<String, List<String>> myMap = new HashMap<>();

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Number 4 - NOTE: Type Inference for Generic Instance Creation
Writing new HashMap() (without diamond operator) will still use the
raw type of HashMap (compiler warning)

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Number 5:

Underscores in Numeric Literals

long creditCardNumber = 1234_5678_9012_3456L;
long socialSecurityNumber = 1977_05_18_3312L;
float pi = 3.14_15F;
long hexBytes = 0xFF_EC_DE_5E;
long hexWords = 0xCAFE_BABE;
long maxLong = 0x7fff_ffff_ffff_ffffL;
long bytes = 0b11010010_01101001_10010100_10010010;

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Number 5 - NOTE: Underscores in Numeric Literals
You can place underscores only between digits; you cannot place
underscores in the following places:

At the beginning or end of a number
Adjacent to a decimal point in a floating point literal
Prior to an F or L suffix

In positions where a string of digits is expected

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Java SE 7 – Concurrent Utilities

Number 6:

Fork/Join Framework (JSR 166)

” a lightweight fork/join framework with flexible and reusable
synchronization barriers, transfer queues, concurrent linked
double-ended queues, and thread-local pseudo-random-number
generators.”

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Number 6:


if (my portion of the work is small enough)
do the work directly
else
split my work into two pieces invoke the two pieces and
wait for the results

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Number 6:

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Number 6:


New Classes
•

ForkJoinTask

•

RecursiveTask

•

RecursiveAction

•

ThreadLocalRandom

•

ForkJoinPool

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Java SE 7 – Filesystem API

Number 7:

NIO 2 Filesystem API (Non-Blocking I/O)

Better supports for accessing file systems such and support for
custom file systems (e.g. cloud file systems)

Access to metadata such as file permissions
More effecient support when copy/moving files
Enchanced Exceptions when working on files, i.e.
file.delete() now throws IOException (not just Exception)

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Java SE 7 – JVM Enhancement

Number 8:

Invoke Dynamic (JSR292)

Support for dynamic languages so their performance levels is near to
that of the Java language itself

At byte code level this means a new operand (instruction) called
invokedynamic
Make is possible to do efficient method invocation for dynamic
languages (such as JRuby) instead of statically (like Java) .
Huge performance gain

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Number 9:

G1 and JVM optimization

G1 more predictable and uses multiple cores better than CMS
Tiered Compilation –Both client and server JIT compilers are
used during starup
NUMA optimization - Parallel Scavenger garbage collector has
been extended to take advantage of machines with NUMA (~35%
performance gain)
Escape Analysis - analyze the scope of a new object's and decide
whether to allocate it on the Java heap
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Number 9:

Escape Analysis

public class Person {
private String name; private int age;
public Person(String personName, int personAge) {
name = personName; age = personAge; }
public Person(Person p) {
this(p.getName(), p.getAge());
}
}
public class Employee {
private Person person; // makes a defensive copy to protect against modifications by caller
public Person getPerson() {
return new Person(person)
};
public void printEmployeeDetail(Employee emp) {
Person person = emp.getPerson(); // this caller does not modify the object, so defensive copy was unnecessary
System.out.println ("Employee's name: " + person.getName() + "; age: " + person.getAge()); }
}
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Java SE 7 - Networking
Number 10: Support for SDP 
Socket Direct Protocol (SDP) enables JVMs to use Remote Direct
Memory Access (RDMA). RDMA enables moving data directly
from the memory of one computer to another computer,
bypassing the operating system of both computers and resulting
in significant performance gains.
The result is High throughput and Low latency (minimal delay
between processing input and providing output) such as you
would expect in a real-time application.

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Java SE 7 - Networking

Number 10 - NOTE: Support for SDP
The Sockets Direct Protocol (SDP) is a networking protocol
developed to support stream connections over InfiniBand fabric.

Solaris 10 5/08 has support for InfiniBand fabric (which enables
RDMA). On Linux, the InfiniBand package is called OFED
(OpenFabrics Enterprise Distribution).

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Java SE 7

A complete list of all new features can be seen on
http://www.oracle.com/technetwork/java/javase/jdk7-relnotes418459.html

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Java SE 8
Some features where left out in Java 7; most important are Project
Lambda (closures) and Project Jigsaw (modules) targeted for
Java 8 (late 2012)
Lambdas (and extension methods) will probably be the biggest single
change ever made on the JVM. Will introduce a powerful
programming model, however it comes with a great deal of
complexity as well.
Modules will made it easier to version modules (no more JAR-hell)
and introduce a new way of defining classpaths
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Java SE 7 & 8

Questions?

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