2. Sreyachandran.v
Sreya.chandran31@gmail.com
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JVM

3. Disclaimer: This presentation is prepared by trainees of
baabtra as a part of mentoring program. This is not official
document of baabtra –Mentoring Partner
Baabtra-Mentoring Partner is the mentoring division of baabte System Technologies Pvt . Ltd

4. JAVA
• Java programming language was originally developed by Sun
Microsystems.
• Object Oriented : In Java, everything is an Object based.
• Platform independent.

5. Virtual Machine
• A virtual machine (VM) is a software implementation of a
machine (for example, a computer) that executes programs
like a physical machine.
• Virtual machines are separated into two major
classifications:
system virtual machine and process virtual machine.

6. JVM
• A Java virtual machine (JVM) is a process virtual
machine that can execute java byte code.
• JVM converts Java byte code into machine language and
executes it.
• JVM is platform dependent : JVMs are available for many
hardware and software platforms.
• JVM gives Java the flexibility of platform independence.

7. Diagram of JVM
Java source code Byte codeJava compiler
Java Virtual Machine
Java Interpreter
Computer Operating System
Byte code loaded into JVM

8. Block Diagram
Class loader sub
system
Execution engine

9. Class loader
• All Java virtual machines include one class loader that is
embedded in the virtual machine.
• Class loader loads java classes into java virtual machine.
• Class loader reads bytecode and creates the instance of
java.lang.class.

10. Execution engine
• The execution engine helps JVM to convert bytecode into
machine code.
• A mechanism responsible for executing the instructions
contained in the methods of loaded classes.

11. Stack
• Stack stores various method arguments and local variables of
any method .
• There are three registers that help in stack manipulation.
– Vars register
– Frame register
– Optop register

12. Sections in stack
• Local variable
– This section contain all local variable being used by current method.
• Execution environment
– Execution section is used to maintain the operation of stack itself.
• Operand stack
– The operand stack is used as a work space by bytecode instruction.

13. Method Area
• This is the area where byte code is placed.
• The program counter points to the next instruction in the
method area.
• After the execution of an instruction , JVM set pc to next
instruction.

14. Garbage Collected Heap
• The object in java program are stored in Garbage collected
heap.
• Arrays in java program are objects, hence they also stored
in heap.
• Java does not have a free operator to free any previously
allocated memory.
• Java done this automatically by Garbage collection
mechanism.

15. • JRE is an acronym for Java Runtime Environment.
• Java Runtime Environment contains JVM, class libraries, and
other supporting files.
• It does not contain any development tools such as compiler,
debugger, etc
JRE

16. JDK
• JDK is an acronym for Java Development Kit . It physically
exists . It contains JRE + development tools.

17. JIT
• Just-in-time Compiler -is the part of the Java Virtual Machine
(JVM) that is used to speed up the execution time.
• JIT compiles parts of the byte code that have similar
functionality at the same time, and hence reduces the amount
of time needed for compilation.

18. Is java a compiled or interpreted
language ?
• Java is a compiled language because the source code is
converted into byte code.
• Java is an interpreted language because the byte code is
interpreted by a virtual machine.

19. THANK YOU

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