The operand stack is organized as an array of words like a local variable array.JVM uses operand stack as workspace like rough work or we can say for storing intermediate calculation’s result.For Example: Let us consider a class Example having a method bike() then the local variable array will be as shown in the below diagram:.The parameters are placed into the local variable array first, in the order in which they are declared.But most of the JVM gives 1 slot for Boolean values in the local variable array. But the way of storing Boolean values is varied from JVM to JVM.Byte, short, and char values will be converted to int type before storing and occupy 1 slot i.e.Values of double and long occupy 2 consecutive entries in the array i.e.Values of type int, float, and reference occupy 1 entry or slot in the array i.e.Each slot or entry in the array is of 4 Bytes.It contains all parameters and local variables of the method.The local variables part of the stack frame is organized as a zero-based array of words.It creates a stack frame of the proper size for invoked method and pushes it onto the Java stack. When JVM invokes a Java method, first it checks the class data to determine the number of words (size of the local variable array and operand stack, which is measured in words for each individual method) required by the method in the local variables array and operand stack. The stack frame basically consists of three parts: Local Variable Array, Operand Stack & Frame Data.

Each entry in the stack is called Stack Frame or Activation Record.

The data stored in the stack is available for the corresponding thread and not available to the remaining threads. After completing all method calls the stack becomes empty and that empty stack is destroyed by the JVM just before terminating the thread. After completing a method, the corresponding entry from the stack is removed. Every method call performed by that thread is stored in the corresponding run-time stack including parameters, local variables, intermediate computations, and other data. And stack for a particular thread may be termed as Run – Time Stack. The Java virtual machine only performs two operations directly on Java stacks: it pushes and pops frames. The memory for a Java Virtual Machine stack does not need to be contiguous. ISRO CS Syllabus for Scientist/Engineer Examįor every thread, JVM creates a separate stack at the time of thread creation.ISRO CS Original Papers and Official Keys.GATE CS Original Papers and Official Keys.

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