I will begin our blog on Java Tutorial with an incredibly important aspect of java development:  memory management.  The importance of this topic should not be minimized as an application's performance and footprint size are at stake.

From the outset, the Java Virtual Machine (JVM) manages memory via a mechanism known as Garbage Collection (GC).  The Garbage collector

• Manages the heap memory.   All obects are stored on the heap; therefore, all objects are managed.  The keyword, new, allocates the requisite memory to instantiate an object and places the newly allocated memory on the heap.  This object is marked as live until it is no longer being reference.
• Deallocates or reclaims those objects that are no longer being referened. 
• Traditionally, employs a Mark and Sweep algorithm.  In the mark phase, the collector identifies which objects are still alive.  The sweep phase identifies objects that are no longer alive.
• Deallocates the memory of objects that are not marked as live.
• Is automatically run by the JVM and not explicitely called by the Java developer.  Unlike languages such as C++, the Java developer has no explict control over memory management.
• Does not manage the stack.  Local primitive types and local object references are not managed by the GC.

So if the Java developer has no control over memory management, why even worry about the GC?  It turns out that memory management is an integral part of an application's performance, all things being equal.  The more memory that is required for the application to run, the greater the likelihood that computational efficiency suffers. To that end, the developer has to take into account the amount of memory being allocated when writing code.  This translates into the amount of heap memory being consumed.

Memory is split into two types:  stack and heap.  Stack memory is memory set aside for a thread of execution e.g. a function.  When a function is called, a block of memory is reserved for those variables local to the function, provided that they are either a type of Java primitive or an object reference.  Upon runtime completion of the function call, the reserved memory block is now available for the next thread of execution.  Heap memory, on the otherhand, is dynamically allocated.  That is, there is no set pattern for allocating or deallocating this memory.  Therefore, keeping track or managing this type of memory is a complicated process. In Java, such memory is allocated when instantiating an object:

String s = new String();  // new operator being employed
String m = "A String";    /* object instantiated by the JVM and then being set to a value.  The JVM
calls the new operator */

As much as we love to assume free Wi-Fi is secure, this is far from the truth. Because you are attaching to a service many others are connected to as well, without security measures, your device can be hacked, especially if the network is unencrypted. Because this encryption involves handing out a 26-character hexadecimal key to every individual wanting to use that network, most places opt for ease of access over security. And even with a secure network, your information is vulnerable to everyone else who has the password and is on the network.

This may not seem like such a big deal and many people don’t believe they have anything to hide on their personal devices, but remember what you use on those devices. Chances are your e-mail is attached as well as all other social media sites. You may have apps that track your finances or private messages to certain others that you would never want anyone else to see. Luckily, there are steps that can be taken to reduce and prevent any unwanted information grabbers from accessing your personal information.

To start, go through your computer’s settings in order to verify your operating system’s security functions are all set to offer the highest protection. Open up the Control Panel and double check that your Firewall is enabled for both private and public networks. Then, go to Network and Sharing to open Change advanced sharing settings. In here, you can turn off file and printer sharing and network discovery for public networks.

One of the most important things to watch for is HTTPS. Hypertext Transfer Protocol Secure ensures secure communication across the web. Many of the major email systems use this when you log in (as another layer of password protection) but drop the security as soon as the login is complete. To keep this going, HTTPS Everywhere is a browser extension that gives you a secure connection when browsing some of the more popular sites. It can also be programmed for other sites you like to visit that don’t use HTTPS.

Not every place on the internet provides the choice of HTTPS, and VPNs are there to fill in the security gap. Virtual Private Networks allows data to be sent and received through public access points as if it were directly connected to a secure network. Many businesses offer this for company devices, but if you are an individual looking for that kind of security, ProXPN is a free version that can be upgraded. Unfortunately, it limits your speed, but other choices include VPNBook, OpenVPN Shield Exchange, and OkayFreedom.

With these three steps implemented, secure public Wi-Fi can be achieved. No longer will you have to worry about connecting in an unsure environment with strangers, never knowing if your information is being stolen. With all of the options free of charge, it is also an affordable means of protecting yourself that only takes a little time and effort to implement and guarantee safety.

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A business rule is the basic unit of rule processing in a Business Rule Management System (BRMS) and, as such, requires a fundamental understanding. Rules consist of a set of actions and a set of conditions whereby actions are the consequences of each condition statement being satisfied or true. With rare exception, conditions test the property values of objects taken from an object model which itself is gleaned from a Data Dictionary and UML diagrams. See my article on Data Dictionaries for a better understanding on this subject matter.

A simple rule takes the form:

if condition(s)

then actions.

An alternative form includes an else statement where alternate actions are executed in the event that the conditions in the if statement are not satisfied:

if condition(s)

then actions

else alternate_actions

It is not considered a best prectice to write rules via nested if-then-else statements as they tend to be difficult to understand, hard to maintain and even harder to extend as the depth of these statements increases; in other words, adding if statements within a then clause makes it especially hard to determine which if statement was executed when looking at a bucket of rules. Moreoever, how can we determine whether the if or the else statement was satisfied without having to read the rule itself. Rules such as these are often organized into simple rule statements and provided with a name so that when reviewing rule execution logs one can determine which rule fired and not worry about whether the if or else statement was satisfied. Another limitation of this type of rule processing is that it does not take full advantage of rule inferencing and may have a negative performance impact on the Rete engine execution. Take a class with HSG and find out why.

Rule Conditions