Red Hat NETSCAPE ENTERPRISE SERVER 6.0 - NSAPI PROGRAMMER GUIDE Manuel d'utilisateur télécharger pdf (Page 100)

Differences Between JavaScript and Java

100 iPlanet Web Server, Enterprise Edition Programmer’s Guide to Servlets • May 2001

Java is a class-based programming language designed for fast execution and type

safety. Type safety means, for instance, that you can’t cast a Java integer into an

object reference or access private memory by corrupting Java bytecodes. Java’s

class-based model means that programs consist exclusively of classes and their

methods. Java’s class inheritance and strong typing generally require tightly

coupled object hierarchies. These requirements make Java programming more

complex than JavaScript authoring.

Table B-1 JavaScript and Java compared

JavaScript Java

Interpreted (not compiled) by client. Compiled bytecodes downloaded from

server, executed on client.

A scripting language that supports objects. An object-oriented language.

No distinction between types of objects.

Inheritance is through the prototype

mechanism, and properties and functions

can be added to any object dynamically.

Objects are divided into classes and

instances with all inheritance through the

class hierarchy. Classes and instances

cannot have properties or methods added

dynamically.

Functions may be inside classes but do not

have to be.

Every method must be inside a class.

Code integrated with, and embedded in,

HTML.

Code distinct from HTML, although JSPs

can contain HTML tags.

Loosely cast: variable and function types

not declared (dynamic typing).

Tightly cast: variable and method types

must be declared (static typing).

Cannot automatically write to hard disk. Cannot automatically write to hard disk.

Semicolons at the ends of statements are

optional.

All statements must end with a semicolon

(;).

1 2 ... 95 96 97 98 99 100 101 102 103 104 105 ... 123 124

Pas de commentaire

Red Hat NETSCAPE ENTERPRISE SERVER 6.0 - NSAPI PROGRAMMER GUIDE Manuel d'utilisateur Page 100