How are java objects stored in memory?

The memory allocation in java for any type of object is based on the concept of ‘Dynamic Memory Allocation’. The dynamically memory allocated on the heap to objects as they created. As long as , object has a reference variable referring to it, it is safe on the heap. But if there are no references to the object, it becomes eligible for garbage collection.

In java, if we declare a variable of a class type, the memory Doesn’t get allocated for the object and only the reference is created. To allocate memory to objects, we need to use new().

For Example

Following program fails in the compilation.

class Random{
      void show()
          {
           System.out.printIn("Random::show() called);
           }
          }
      public class Main 
          {
            public static void main(String[] args)  
                {
                 Random num;
                  num.show();// Error here because num is not initialized
                }     
          }

In the above program, the compiler shows an error “because num is not initialized“.

Allocating memory using new() to handle an error.

class Random {
     void show()
            {
              system.out.printIn("Random::show() clalled");
            }
}
public class Main{
        public static void main(String[] agrs)
         Random num = new Random();
          num.show();
// No error Because all objects are dynamically allocated
}

Throughout the application lifecycle. The objects can be created and stored in the heap memory. At the time of the setup of the java virtual machine, heap automatically created.

There are two type od memory area.

  • Thread Stacks
  • Heap

Thread Stacks:

Thread Stack is specific memory area that contains local variables, methods call information etc. Java virtual machine stacks can be fix size or variable size. If computation in a thread more than its stack size limit then JVM throws “StackOverflow” Error and exits.

Heap

Heap used to store all the created objects. Garbage collector reclaims heap storage for objects and objects never explicitly deallocated. The JVM is not using any automatic storage management system.it may vary as per the system requirements.

Static variables are stored on heap area and objects stored on the heap can be referred by references stored in thread stack.

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How are java objects stored in memory?

How are java objects stored in memory?

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