Java 简明教程
Java - Overview
Java 编程语言最初由 Sun Microsystems 开发，由 James Gosling 发起，并于 1995 年作为 Sun Microsystems 的 Java 平台（Java 1.0 [J2SE]）的核心组件发布。
Java programming language was originally developed by Sun Microsystems which was initiated by James Gosling and released in 1995 as core component of Sun Microsystems' Java platform (Java 1.0 [J2SE]).
Java Standard Edition 最新版本是 Java SE 8。随着 Java 的进步及其广泛普及，构建了多种配置以适应各种类型的平台。例如：用于企业应用程序的 J2EE，用于移动应用程序的 J2ME。
The latest release of the Java Standard Edition is Java SE 8. With the advancement of Java and its widespread popularity, multiple configurations were built to suit various types of platforms. For example: J2EE for Enterprise Applications, J2ME for Mobile Applications.
新 J2 版本分别更名为 Java SE、Java EE 和 Java ME。Java 有保证 Write Once, Run Anywhere.
The new J2 versions were renamed as Java SE, Java EE, and Java ME respectively. Java is guaranteed to be Write Once, Run Anywhere.
Java 是 −
Java is −
-
Object Oriented − In Java, everything is an Object. Java can be easily extended since it is based on the Object model.
-
Platform Independent − Unlike many other programming languages including C and C++, when Java is compiled, it is not compiled into platform specific machine, rather into platform independent byte code. This byte code is distributed over the web and interpreted by the Virtual Machine (JVM) on whichever platform it is being run on.
-
Simple − Java is designed to be easy to learn. If you understand the basic concept of OOP Java, it would be easy to master.
-
Secure − With Java’s secure feature it enables to develop virus-free, tamper-free systems. Authentication techniques are based on public-key encryption.
-
Architecture-neutral − Java compiler generates an architecture-neutral object file format, which makes the compiled code executable on many processors, with the presence of Java runtime system.
-
Portable − Being architecture-neutral and having no implementation dependent aspects of the specification makes Java portable. Compiler in Java is written in ANSI C with a clean portability boundary, which is a POSIX subset.
-
Robust − Java makes an effort to eliminate error prone situations by emphasizing mainly on compile time error checking and runtime checking.
-
Multithreaded − With Java’s multithreaded feature it is possible to write programs that can perform many tasks simultaneously. This design feature allows the developers to construct interactive applications that can run smoothly.
-
Interpreted − Java byte code is translated on the fly to native machine instructions and is not stored anywhere. The development process is more rapid and analytical since the linking is an incremental and light-weight process.
-
High Performance − With the use of Just-In-Time compilers, Java enables high performance.
-
Distributed − Java is designed for the distributed environment of the internet.
-
Dynamic − Java is considered to be more dynamic than C or C++ since it is designed to adapt to an evolving environment. Java programs can carry extensive amount of run-time information that can be used to verify and resolve accesses to objects on run-time.
Hello World using Java Programming
为了让你对 Java 编程产生一些兴趣，我将为你提供一个小型传统的 C 编程 Hello World 程序，你可以使用演示链接尝试一下。
Just to give you a little excitement about Java programming, I’m going to give you a small conventional C Programming Hello World program, You can try it using Demo link.
public class MyFirstJavaProgram {
/* This is my first java program.
* This will print 'Hello World' as the output
*/
public static void main(String []args) {
System.out.println("Hello World"); // prints Hello World
}
}History of Java
詹姆斯·高斯林在 1991 年 6 月发起了 Java 语言项目，用于在其众多的机顶盒项目之一中使用。这门语言最初被称为“Oak”，以高斯林办公室外的一棵橡树命名，也曾被称为“Green”，后来从一组随机单词中更名为 Java。
James Gosling initiated Java language project in June 1991 for use in one of his many set-top box projects. The language, initially called 'Oak' after an oak tree that stood outside Gosling’s office, also went by the name 'Green' and ended up later being renamed as Java, from a list of random words.
Sun 于 1995 年发布了第一个公共实施版本 Java 1.0。它承诺*Write Once, Run Anywhere*（WORA），提供了在流行平台上免费运行时。
Sun released the first public implementation as Java 1.0 in 1995. It promised Write Once, Run Anywhere (WORA), providing no-cost run-times on popular platforms.
2006 年 11 月 13 日，Sun 根据 GNU 通用公共许可证 (GPL) 的条款发布了大部分 Java 作为自由和开放源代码软件。
On 13 November, 2006, Sun released much of Java as free and open source software under the terms of the GNU General Public License (GPL).
2007 年 5 月 8 日，Sun 完成了该过程，使 Java 的所有核心代码成为自由和开源，除了 Sun 没有持有其版权的一小部分代码。
On 8 May, 2007, Sun finished the process, making all of Java’s core code free and open-source, aside from a small portion of code to which Sun did not hold the copyright.
Tools You Will Need
为了执行本教程中讨论的示例，你需要一台奔腾 200 兆赫计算机，最小内存为 64 MB（建议内存为 128 MB）。
For performing the examples discussed in this tutorial, you will need a Pentium 200-MHz computer with a minimum of 64 MB of RAM (128 MB of RAM recommended).
你还需要以下软件 −
You will also need the following softwares −
-
Linux 7.1 or Windows xp/7/8 operating system
-
Java JDK 8
-
Microsoft Notepad or any other text editor
本教程将提供使用 Java 创建 GUI、网络和 Web 应用程序的必要技能。
This tutorial will provide the necessary skills to create GUI, networking, and web applications using Java.