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 */

For many people, one of the most exciting and challenging career choices is computer programming. There are several ways that people can enter the computer programming profession; however, the most popular method has traditionally been the educational route through an educational institution of higher learning such as a college or technical school.

Even though many people think of computer programmers as individuals with a technical background, some programmers enter the computer programming profession without a structured technical background. In addition, after further investigation several interesting facts are uncovered when a profile of the best computer programmers is analyzed.

When observing how the top programmers in the profession work, there are four characteristics that tend to separate the top programmers from the average programmers. These four characteristics are:

1.Creativity.
2.Attention To Detail.
3.Learns New Things Quickly.
4.Works Well With Others.

Creativity.

Being a top computer programmer requires a combination of several unique qualities. One of these qualities is creativity. In its very essence, computer programming is about creating programs to accomplish specific tasks in the most efficient manner. The ability to develop computer code to accomplish tasks takes a certain level of creativity. The top computer programmers tend to have a great deal of creativity, and they have the desire to try things in a variety of ways to produce the best results for a particular situation.

Attention To Detail.

While creativity is important for top programmers an almost opposite quality is needed to produce great computer programs on a consistent basis, this quality is attention to detail. The very nature of computer programming requires the need to enter thousands of lines of computer programming code. What separates many top programmers from average programmers is the ability to enter these lines of code with a minimum amount of errors and just as importantly test the code to catch any unseen errors. Top computer programmers have the necessary attention to detail to successfully create and enter the necessary computer code project after project.

Learns New Things Quickly.

The technology field is constantly changing. Almost daily new technology innovations are being developed that require computer programmers to learn new technology or enhancements to current technology on a regular basis. The top computer programmers are able to learn new technology or enhancements quickly, and then they are able to apply what has been learned to their current and future programming projects in a seamless manner.

Works Well With Others.

There are several differences between top computer programmers and other programmers. However, one of the biggest differences is the ability to work well with others. By its very nature, computer programming requires programmers to spend a lot of time alone developing computer code, but the top computer programmers are able to excel at this aspect of computer programming along with being able to work well with other people.

Regarding computer programmers, the top programmers approach and handle their jobs differently than other programmers, and these differences set them apart from the other programmers. For any average programmers who have the desire to excel as a computer programmer, they must understand and embrace the characteristics of top programmers.

Related:

How important is it to exercise for people in technology that sit for hours on end?

What are a few unique pieces of career advice that nobody ever mentions?

Back in the late 90's, there were a number of computer scienctists claiming to know java in hopes of landing a job for $80k+/year.  In fact, I know a woman you did just that:  land a project management position with a large telecom and have no experience whatsoever.  I guess the company figured that some talent was better than no talent and that, with some time and training, she would be productive.  Like all gravey train stories, that one, too, had an end.  After only a year, she was given a pink slip.

Not only are those days over, job prospects for the IT professional have become considerably more demanding.  Saying you know java today is like saying you know that you have expertise with the computer mouse; that's nice, but what else can you do.   This demand can be attributed to an increase in global competition along with the introduction of a number of varied technologies.   Take .NET, Python, Ruby, Spring, Hibernate ... as an example;  most of them, along with many others, are the backbone of the IT infrastructure of most mid-to-large scale US corporations.  Imagine the difficulty in finding the right mix of experience, knowledge and talent to support, maintain and devlop with such desparate technologies.

Well imagine no more.  According to the IT Hiring Index and Skills Report, seventy percent of CIO’s said it's challenging to find skilled professionals today.  If we add the rapid rate of technological innovation into the mix of factors affecting more businesses now than ever before, it’s understandable that the skill gap is widening.  Consider this as well:  the economic downturn has forced many potential retires to remain in the workforce.  This is detailed in MetLife's annual Study of Employee Benefits which states that“more than one-third of surveyed Baby Boomers (35%) say that as a result of economic conditions they plan to postpone their retirement.”  How then does the corporation hire new, more informed/better educated talent?    Indeed, the IT skills gap is ever widening.

In order to compensate for these skill discrepencies, many firms have resorted to hire the ideal candidates by demanding they possess a christmas wish list of expertise in a variety of different IT disciplines.  It would not be uncommon that such individuals have a strong programming background and are brilliant DBA's.  What about training?  That is certainly a way to diminish the skills gap.

Memory management is always a priority in pretty much any programming language you would want to use. In the lower level languages such as C, there are a number of functions which help you manage the memory your application uses, but they are not the easiest to use. Some of the more modern programming languages such as Python, Ruby, Perl, and of course the subject of this article, Javascript all have a built in feature called garbage collection.

Garbage collection essentially means that the languages compiler will automatically free the memory being occupied by unused variables and objects, but there is no telling when this could occur. It is purely down to the compiler to decide when the garbage collection process should be initiated.