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 */

In programming, memory leaks are a common issue, and it occurs when a computer uses memory but does not give it back to the operating system. Experienced programmers have the ability to diagnose a leak based on the symptoms. Some believe every undesired increase in memory usage is a memory leak, but this is not an accurate representation of a leak. Certain leaks only run for a short time and are virtually undetectable.

Memory Leak Consequences

Applications that suffer severe memory leaks will eventually exceed the memory resulting in a severe slowdown or a termination of the application.

How to Protect Code from Memory Leaks?

Preventing memory leaks in the first place is more convenient than trying to locate the leak later. To do this, you can use defensive programming techniques such as smart pointers for C++.  A smart pointer is safer than a raw pointer because it provides augmented behavior that raw pointers do not have. This includes garbage collection and checking for nulls.

If you are going to use a raw pointer, avoid operations that are dangerous for specific contexts. This means pointer arithmetic and pointer copying. Smart pointers use a reference count for the object being referred to. Once the reference count reaches zero, the excess goes into garbage collection. The most commonly used smart pointer is shared_ptr from the TR1 extensions of the C++ standard library.

Static Analysis

The second approach to memory leaks is referred to as static analysis and attempts to detect errors in your source-code. CodeSonar is one of the effective tools for detection. It provides checkers for the Power of Ten coding rules, and it is especially competent at procedural analysis. However, some might find it lagging for bigger code bases.

How to Handle a Memory Leak

For some memory leaks, the only solution is to read through the code to find and correct the error. Another one of the common approaches to C++ is to use RAII, which an acronym for Resource Acquisition Is Initialization. This approach means associating scoped objects using the acquired resources, which automatically releases the resources when the objects are no longer within scope. RAII has the advantage of knowing when objects exist and when they do not. This gives it a distinct advantage over garbage collection. Regardless, RAII is not always recommended because some situations require ordinary pointers to manage raw memory and increase performance. Use it with caution.

The Most Serious Leaks

Urgency of a leak depends on the situation, and where the leak has occurred in the operating system. Additionally, it becomes more urgent if the leak occurs where the memory is limited such as in embedded systems and portable devices.

To protect code from memory leaks, people have to stay vigilant and avoid codes that could result in a leak. Memory leaks continue until someone turns the system off, which makes the memory available again, but the slow process of a leak can eventually prejudice a machine that normally runs correctly.

Related:

The Five Principles of Performance

In Demand IT Skills

Every programming language has a mechanism to allow the programmer to create variables which hold custom data entered in by either the coder themselves or by the user of the application.

Regardless of whether you’re new to programming or not, you will have used variables and you should understand that in javascript they can hold any value such as a number or a string of text.

There is also another type of variable called an Array. Now, depending on who you talk to, some will say an array is actually an object, while others say it is a variable. Neither one is wrong but for the sake of simplicity we’ll refer to it as a variable.

Now, arrays are special because they can hold multiple values as opposed to standard variables which can only hold a single value at one time. If you can, try and imagine that your computer’s memory is made up of thousands of little boxes, and each of those boxes has an address which javascript will use to retrieve the array values when needed.

A project manager acts as the primary link between business and technical teams. A project manager is responsible for maintaining the project schedule, developing project estimates, working with external teams and tracking project issues. The project manager belongs to either the technical team or the project management office (PMO). The project manager works with business teams, technical teams, business counterparts, testing resources, vendors and infrastructure teams.

A project manager is often challenged with diagonally opposite views from the business side and technical side. A project manager’s success depends on balancing the needs and emotions of both sides.

Understanding the Requirements
A project manager must familiarize with the project’s requirements as defined by the business or product managers. This will help you understand the business vision behind the project. You will need this knowledge while negotiating with the technical teams.

Understanding the Technical Landscape
A project manager must also understand the technical systems, resource skills and infrastructure capabilities available for the project. Business teams come up with expectations that are sometimes beyond the capabilities of the technology team. It is the responsibility of the project manager to understand the technical capabilities available to the project.

Walkthrough of Business Requirements
This is a critical step in the project delivery process. The project manager must invite members from the business team, technical team, testing team, infrastructure team and vendors. The project manager must encourage the various stakeholders to ask questions about the requirements. Any prototypes available must be demonstrated in this meeting. The project manager must find answers to all questions resulting from the requirements walkthrough. The project manager must get the final version of the requirements approved by all stakeholders.

Managing Conflicts in Timelines and Budgets
All project managers will face the conflicts arising from shortened timelines and limited budgets. Business teams typically demand many features that are nearly impossible to deliver within short timeframes. The project manager must work with business and technical teams to prioritize the requirements. If the project is executed in a product development organization, then the project manager could utilize agile methodologies to deliver projects incrementally. In this case, the project manager may be required to act as a scrum master to facilitate scrum meetings between various stakeholders.

The Art of Saying “No”
As a project manager, you may be forced to say “no” to demands from both business and technology teams. However, it is important to create a win-win situation for all parties when you are faced with conflicting demands. You can work with the stakeholders individually before bringing all parties together. Most stakeholders prefer to work together. The success of a project manager depends on how effectively he or she can bring out the best in everyone, driving everyone towards a common goal.

Finally, the job of a project manager is not to satisfy the demands from all corners. The project manager must identify the essential deliverables that will meet the business needs, with a solid understanding of what is possible within the limits of technology.

Related:

Smart Project Management: Best Practices of Good Managers

Is Agism an Issue in IT?