15-11-2012, 05:58 PM
Java and the JVM
JavaJVM.ppt (Size: 328.5 KB / Downloads: 20)
History of a Young Java
1992 Oak for a PDA on a SPARC (*7)
1995 Official release as Java – Internet
1997 picoJava – Sun’s Java processor
1998 RTSJ specification start as JSR-01
1999 split into J2SE and J2EE
2000 J2ME
2002 RTSJ final release
2002 first version of JOP ;-)
Java features
Simple and object oriented
Look and feel of C
Simplified object model with single inheritance
Portability
Java compiler generates bytecodes
Runtime systems for various platforms
Size and behavior of basic data types defined
Write once, run/debug anywhere
Java Technology
The Java programming language
The library (JDK)
The Java virtual machine (JVM)
Instruction set
Binary format
Verification
Objects
Everything belongs to an object (or a class)
No global variables
Namespace for objects
Single inheritance
Interfaces
Allocated on the heap
Shared among threads
No free() – garbage collector
The Java Virtual Machine
An abstract computing machine that executes bytecode programs
An instruction set and the meaning of those instructions – the bytecodes
A binary format – the class file format
An algorithm to verify the class file
Implementations of the JVM
Interpreter
Simple, compact
Slow
Just-in-time compilation
State-of-the-art for desktop/server
Too resource consuming in embedded systems
Batch compilation
Hardware implementation
Our topic!