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  • 1. Sreyachandran.v JVM
  • 2. 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
  • 3. JAVA • Java programming language was originally developed by Sun Microsystems. • Object Oriented : In Java, everything is an Object based. • Platform independent.
  • 4. 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.
  • 5. 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.
  • 6. Diagram of JVM Java source code Byte codeJava compiler Java Virtual Machine Java Interpreter Computer Operating System Byte code loaded into JVM
  • 7. Block Diagram Class loader sub system Execution engine
  • 8. 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.
  • 9. 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.
  • 10. 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
  • 11. 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.
  • 12. 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.
  • 13. 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.
  • 14. • 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
  • 15. JDK • JDK is an acronym for Java Development Kit . It physically exists . It contains JRE + development tools.
  • 16. 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.
  • 17. 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.
  • 18. THANK YOU
  • 19. Want to learn more about programming or Looking to become a good programmer? Are you wasting time on searching so many contents online? Do you want to learn things quickly? Tired of spending huge amount of money to become a Software professional? Do an online course @ We put industry standards to practice. Our structured, activity based courses are so designed to make a quick, good software professional out of anybody who holds a passion for coding.
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