CIS 26
Object-Oriented Programming
Lecture 01-1 - Intro To The Java Environment
The Java Platform and Architecture
- JDK - Java Development Kit
- Software distribtuion containing tools for developing and running Java applications
- Various flavors
- J2SE - Standard Edition
- Desktop applications
- What we're going to use
- J2EE - Enterprise Edition
- Server-based applications
- J2ME - Micro Edition
- Embedded systems
- Resource contraints
- JRE - Java Runtime Environment
- Software and classes for running Java application
Program Translation and Execution
- Compilation
- Interpretation
- Combination of the two
- Translation to an intermediate (low-level) format
- One format is byte-code -- similar to machine code
- Interpretation of that low-level format on a virtual machine
- Software simulation of a CPU whose machine language is the byte-code.
- This scheme allows for
- High degree of platform independence
- Fast introduction to new platforms
The JVM - Java Virtual Machine
- Java source is compiled to Java byte code
- The byte code is then executed via
- Interpreter simulating the JVM, or
- JIT - Just-in-time compilation, or
- Java byte-code is compiled to native machine code and executed
- Direct execution - a Java chip is built-- a CPU who native machine language is Java byte code