Garbage collection in java, JAVA Programming

Assignment Help:

The Java programming language is object-oriented and includes automatic garbage collection. Garbage collection is the process of reclaiming memory taken up by unreferenced objects.

Memory Management, Java and Impact on Application Servers

The task of memory management that was always challenging with compiled object-oriented languages such as C++. On the other hand, Java is an interpretive language that takes this memory management out of the hands of developers and gives it directly to the virtual machine where the code will be run. This means that for best performance and stability, it is critical that the Java parameters for the virtual machine be understood and managed by the Application Server deployment team. This section will describe the various parts of the Java heap and then list some useful parameters and tuning tips for ensuring correct runtime stability and performance of Application Servers.

Java Virtual Machines

The Java specification as to what is “standard” for a given release is written and maintained by the JavaSoft division of Sun Microsystems. This specification is then delivered to other JVM providers (IBM, HP, etc). JavaSoft provides the standard implementation on Windows, Solaris, and LINUX. Other platforms are required to deliver the code functionality but their JVM options can be different. Java options that are preceded with “-X” or “-XX” are typically platform-specific. That being said, many options are used on all platforms. One must read in detail the README notes from the various releases on various platforms to be kept up-to-date with the variations. This guide will mention the most critical ones and distinguish between those which are implemented on most platforms and those which are platform-specific.

The Java Heap

The Java heap is divided into three main sections: Young Generation, Old Generation and the Permanent Generation as shown in the figure below.

 

Also, not shown here, is another area called the Code Cache which is typically about 50Mb in Size.

 

HotSpot VM

 

The HotSpot VM is the garbage collector that comes with the JavaSoft virtual machine. Its specification is delivered to all JVM providers (HP, IBM, BEA, etc) and the standard implementation is deployed by JavaSoft on Solaris, Windows and LINUX.

 

Default Garbage Collection Algorithms

 

Scavenge Garbage Collection

 

Scavenge Garbage Collection (also known as a Minor Collection) occurs when the Eden Space is full. By default, it is single-threaded but does not interrupt the other threads working on objects. It can be parallelized starting at Java 1.4 but if too more ParallelGCThreads are specified than CPU cores where the JVM is running, this can cause bottlenecks. For this reason, it is suggested to be careful in when and where to use the parallel options. These will be discussed further on.

 

Full Garbage Collection

 

A Full Garbage Collection (FullGC) occurs under these conditions:

 

The Java application explicitly calls System.gc(). This can be avoided by implementing the -

 

XX:+DisableExplicitGC parameter in the startup command for all Application Server JVMs (Tomcat,Application Server JVM, etc.)


Related Discussions:- Garbage collection in java

How can you performance tune your database?, 1. De normalizes your tables w...

1. De normalizes your tables where required. 2. Proper use of index columns: An index based on numeric parts is more efficient than an index based on character columns. 3. Re

Implement decision tree algorithm using netbeans, Implement Decision Tree A...

Implement Decision Tree Algorithm using Netbeans (Java) & Microsoft Access 2007. "One Level is enough, output should contains gain of each attribute, the selected attribute and

Java program to calculate the commercial value of the stamps, You are asked...

You are asked to write a Java program to calculate the commercial value of the stamps owned by a philatelist. Each philatelist has a name and a collection of stamps. The stamps can

What is jms, Java Message Service: An interface executed by most J2EE conta...

Java Message Service: An interface executed by most J2EE containers to give point-to-point queueing and topic (publish/subscribe) behavior. JMS is frequently used by EJB's that req

Java web programming, Write a JSP to display a table that contains factoria...

Write a JSP to display a table that contains factorials for the numbers from 0 to 10,

What is best algorithm, What is best algorithm? Greedy algorithm is the...

What is best algorithm? Greedy algorithm is the best algorithm as it is n algorithm in which always takes the best immediate, or local solution although searching an answer.

Pogram must work on all realms and all ladders, Project Description: The...

Project Description: The program must work on all realms, all ladders, all cores (4x realms,2x ladders,2x cores) The program must be unpatchable and undetectable If patche

Photo upload feature to android app with google app engine, Include Photo U...

Include Photo Upload feature to Android App with Google App Engine Project Description: I have one small Android App skeleton that requires some features added to and backed

Using polymorphism to write a program to display digital clo, using polymor...

using polymorphism to write a program to display digital clock

Generating Dynamic form, I am having an combox box and values are retrieved...

I am having an combox box and values are retrieved from the database having inputs and labels i want to created the dynamic form accroding to user input on combox box values

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd