Class VirtualMachineError in Java

Java virtual machine is an abstract computer, on which all Java coding runs. Java often refers to a java programming language but actually, Java has four distinct parts-

• Java Coding
• Java class files
• Java virtual machine
• Java APIs(Application Programming Interface)

The emerging infrastructure of smart devices and computer interconnected networks represents a whole new environment for software with an ecosystem where new challenges and new opportunities reside side by side.

Java was originally designed for networks, hence it is suitable for networked environments due to its (Java’s architecture). Java provides a secure, robust, platform-independent program across networks that can run across various devices/computers.

The challenges and opportunity of Java development

• Create a network-centric hardware environment for a wide range of devices (they may or may not always connected to the network). In general, a network has many different kinds of devices attached to it with diverse hardware architectures, operating systems, etc.
• Java provides platform-independent coding. A Java program can run on a wide variety of computers. Unlike a code compiles and run for specific hardware and operating system. These kinds of Java coding are easier and cheaper to develop, administrate and maintain.
• Security– Even though networking is good. It is also a safe passage for hackers who can alter coding. The altered code can help a hacker to steal, destroy the information.
• Java provides customize degrees of security that prevent malicious code to be injected and cause system failures.
• Java also has support for mobile objects. The transmission of code and state across networks. Java supports object mobility via object serialization and Remote Method Invocation.Java Virtual machine’s primary task is to load a class file and execute the byte code the class file is having.

  VirtualMachineError is thrown from an application when the java virtual machine is broken or has run out of resources to continue its operation.

  It is an abstract error type that acts as a superclass for a group of errors related to the Java Virtual Machine. The appropriate subclass of VirtualMachineError is thrown to indicate that the Java virtual machine has encountered an error.

  Virtual Machine dependencies

  Different vendors may provide Java Virtual Machines in a platform-independent way. However, they will surely follow the below rules –

  1. They do not depend upon timely finalization for program correctness.
  2. They do not depend upon thread prioritization for program correctness.

  These two above written rules address the Java Virtual Machine specification for garbage collection and threads. They are allowed in the java machine design principle too!

  In general, all Java Virtual machines should have a garbage collector that maintains the heap. Their implementation may change though. This means the objects of a particulate Java coding can be garbage collected on different times in different virtual machines.

  So, the method finalizer () which are involved by Java Virtual Machine may differ when it can garbage collect the object.

  The Java virtual machines may invoke the finalizer () method upon different scenarios –

  1. If it runs out of the finite resource.
  2. If the thread prioritization is properly optimized. In that case, the higher priority threads get execute along with lower priority threads.

  The structure of the class VirtualMachineError is given as:

  
  public class java.lang.VirtualMachineError extends java.lang.Error{
  //constructor
  public VirtualMachineError();//constructs an empty VirtualMachineError object that is an object with no message specified.
  public VirtualMachineError(String message);//constructs an VirtualMachineError object with the message specified.
  }
  

  The class VirtualMachineError also inherits methods from class Object and Throwable.

  From Object class	From Throwable class
  clone()	fillInStackTrace()
  getClass()	getMessage()
  notify()	printStackTrace()
  wait()	printStackTrace(PrintWriter)
  wait(long, int)	getLocalizedMessage()
  wait(long)	printStackTrace(PrintStream)
  equals(Object)
  toString()
  finalize()
  hashCode()
  notifyAll() VirtualMachineError has the below features:(Exceptions are divided into three modes) Synchronous Delivery Asynchronous Delivery Unchecked Exception Synchronous Delivery Synchronous Delivery of exception is such an exception, which will surely occur in a similar environment irrespective of how many times we execute the program. Example – NullPointerException,StringIndexOutOfBoundException, SocketException. Asynchronous Delivery Asynchronous Delivery of exception is such an exception, which may or may not occur in a similar environment irrespective of how many times we execute the program. In short, there is no certainty or consistency where it will be thrown. Mostly all java VirtualMachineErrors are thrown in asynchronous mode but can be thrown in synchronous mode also. StackOverFlowError is synchronous when a certain method invocation in place but it can be asynchronous when the native method invocation is in place or JVM runs out of memory or other resources. Similarly, OutOfMemoryError is thrown synchronously when an array/object is being created, the class is being initialized or autoboxing or unboxing is taking place, can be asynchronous when a native method invocation happens or JVM runs out of memory or any resources. Unchecked Exceptions Exceptions are two types: Checked Exception- Checked at the compile time. Example- IOException,ClassNotFoundException. Unchecked Exception- UncheckedExceptions can not be caught during compile time. They are declared or caught. Here, all VirtualMachineErrors are unchecked exceptions. OutOfMemoryError can be found, tracked, traced, and subsequently fixed by analyzing Garbage collection logs and manually inspecting the Heapdump. Manual inspection for Garbage collection logs and Heap dump may take a huge time. Popular free tools for Garage collection log analysis are: GCEasy HP JMeter IBM GC analyzer And the popular tools for heap dump analysis are: HeapHero Eclipse MAT Conclusion Finally, VirtualMachineError is thrown as an internal error or some sort of limitation of resources that stops JVM to work properly. By throwing this error JVM actually performs a self-defense mechanism that eventually saves the application from entirely crashing.