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 */

Attempting to create an intelligent entry about Linux for such a wide ranging audience is a bit like trying to compare a presentation on quantum mechanics for physicists while being readable by somebody with a junior high school education.

If you are a *NIX expert, then I suggest you keep on reading so you know how to explain this world to mere mortals.

I called it *nix for a reason. It represents a family of thinking. It is not unlike the difference between the language C and C++. Are there differences between the two? Certainly. And it is not like the difference between COBOL and C.

Years ago when I ran my own vo-tech school I would teach the students there are only two things in life. MS and *NIX. A friend of mine, a genius developer in her own right was aghast.

One of the most recent updates to the iPhone, and more specifically the operating system that is packaged with the iPhone, iOS, brought one of the most fantastic and phenomenal updates ever: an update to Maps. Maps has been used as an application that provides an easy way to find routes, and (obviously) maps about certain areas, businesses in the local vicinity, and also leaving pins on favorited locations, or pins where you have explored, and for many other reasons. However, although Maps has always been a great way to travel with, it has always been redundant to travel with, also. When you used Maps a while ago, you had to route your map, and then manually click each next button as you reached each turn or freeway exit, and the like. So, if you had to turn left on a certain street, you had to tell your phone you had done so, so it would give you the next directions. As a result, it could become very dangerous to always have your phone out, looking at it, while you are on a high-speed freeway. But, the newest update solved that, and brought a great amount of new features.

Using Maps GPS

Using Maps is as easy as it gets. Most of the time, when you are using Maps, you are using it to search for a location, and finding a way to get there. To start off, let’s search for the nearest mall, and routes to get there. Simply search a nearby mall you know about, or search the general word “mall” by tapping on the top text box, and typing in mall, and searching. Pins will drop down on the screen, and locating the mall by zooming into certain streets and locations will help you find the mall you want. Once you find the mall you desire to go to, click on the blue arrow, and scroll down, and tap on the button that says “Directions To Here.”

As a result of tapping on that particular button, a new window should show up asking where your starting location is. On default, this location is your current location; if it is anything else, simply type in the starting location into the top address bar, such as your house. Once you are ready to go, tap on route, and you should be ready to go. Well, not exactly. One of the best features that has been implemented in the new system is suggested routes, and alternative routes. If you don’t like to drive on certain streets, or roads, the system provides you with different methods to get to your destination, which may avoid a road you don’t feel like driving on that certain day, or time, or you simply don’t want to take the freeway. It’s all okay, as Maps provides you with many different routes to take. Once you find the route you want (by tapping on the certain route’s outline), click start, and you should be ready to go. Make sure you turn up your volume so you can hear the directions!

Maps for Alternative Transportation

Viruses, trojans, and other malicious programs are everywhere. There's always a new threat to your computer's security, and many of these threats invade your computer without you even knowing. Most viruses aren't going to loudly announce themselves, so it's important to know the hidden ways in which your computer can become infected.


Infected Files from Other Computers

Whether you're borrowing someone's flash drive or grabbing a file from their computer, your computer can become infected if the file or device you're using already contains a virus, trojan, or other form of malware.

This is a very common issue, and you won't even know there's a problem most of the time. For example, if your computer is connected to other devices on a network, and you decide to pull an important file off of another computer on the network, your computer will become infected if the file you took has a virus attached to it.

Also, if you forgot your flash drive, and you need to use your friend or coworker's device for the day, then even plugging the device into your computer can cause the infection in the flash drive to be transmitted.


Downloading Legitimate Programs

Another way your computer can be secretly infected is when you download a legitimate program and run it. There are numerous legitimate programs on the internet that can help you in many ways. The programs themselves could be infected, though.

Also, one of the most common ways your computer can become infected is when you don't read the fine print before you download a program. Some of them may insist that you install another small program in addition to the one you initially chose. The boxes that you are supposed to click to give your consent may already be clicked.

This small extra program is the one that may carry an infection that will spread to your computer when you run the main program. You may get a lot of good use out of the legitimate program, but the virus attached to the extra hidden program can cause you a lot of trouble.


Using Vulnerable Applications

Security is a serious matter. If even one of the applications you use on your computer is vulnerable to becoming hacked or infected, then your entire computer is at risk and could become secretly infected. Anything from PDF viewing applications to your operating system can become infected if you don't download the latest security patches and keep everything up-to-date.


Not Using Antivirus Software

Antivirus software can protect your computer from a number of viruses, trojans, and other problems. Your computer can become infected in a number of ways, so you need to have good antivirus software to provide strong protection from hidden attacks.


Viruses, trojans, and other malware can infect your computer in a variety of hidden ways. To prevent infection and problems, you need to be careful about what you download, and you should keep your applications secure. Also, find reliable antivirus software to help.

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