Crash Course in Java Computer Science（Java计算机科学课程）.pdfVIP

Crash Course in Java Based on notes from D. Hollinger Based in part on notes from J.J. Johns also: Java in a Nutshell Java Network Programming and Distributed Computing Netprog 2002 Java Intro 1 What is Java? • A programming language. – As defined by Gosling, Joy, and Steele in the Java Language Specification • A platform – A virtual machine (JVM) definition. – Runtime environments in diverse hardware. • A class library – Standard APIs for GUI, data storage, processing, I/O, and networking. Netprog 2002 Java Intro 2 Why Java? • Network Programming in Java is very different than in C/C++ – much more language support – error handling – no pointers! (garbage collection) – threads are part of the language. – some support for common application level protocols (HTTP). – dynamic class loading and secure sandbox execution for remote code. – source code and bytecode-level portability. Netprog 2002 Java Intro 3 Java notes for C++ programmers • Everything is an object. – Every object inherits from java.lang.Object • No code outside of class definition! – No global variables. • Single inheritance – an additional kind of inheritance: interfaces • All classes are defined in .javafiles – one top level public class per file Netprog 2002 Java Intro 4 More for C++ folks • Syntax is similar (control structures are very similar). • Primitive data types similar – bool is not an int. • To print to stdout: – System.out.println();