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 */

Below are two pdf's which discuss and outline the Java Message Service, JMS, tutorial.

One Hour Java Messaging Service Tutorial
Advanced One Hour Java Messaging Service Tutorial

 

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?