Java教程
  • Introduction
  • Getting Started
    • The Java Technology Phenomenon
      • About the Java Technology
      • What Can Java Technology Do?
      • How Will Java Technology Change My Life?
    • The Hello World Application
    • A Closer Look at the Hello World Application
  • Learning the Java Language
    • Object-Oriented Programming Concepts
      • What Is an Object?
      • What Is a Class?
      • What Is Inheritance?
      • What Is an Interface?
      • What Is a package?
    • Language Basics
      • Java Language Keywords
    • Annotations
      • Annotations Basics
      • Declaring an Annotation Type
      • Predefined Annotation Types
      • Repeating Annotations
      • Type Annotations and Pluggable Type Systems
    • Generics
      • Why Use Generics?
      • Generic Types
        • Raw Types
      • Generic Methods
      • Bounded Type Parameters
        • Generic Methods and Bounded Type Parameters
      • Generics, Inheritance, and Subtypes
      • Type Inference
      • Wildcards
        • Upper Bounded Wildcards
        • Unbounded Wildcards
        • Lower Bounded Wildcards
        • Wildcards and Subtyping
        • Wildcard Capture and Helper Methods
        • Guidelines for Wildcard Use
      • Type Erasure
        • Erasure of Generic Types
        • Erasure of Generic Methods
        • Effects of Type Erasure and Bridge Methods
        • Non-Reifiable Types
      • Restrictions on Generics
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  • HelloWorld

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  1. Getting Started

The Hello World Application

PreviousHow Will Java Technology Change My Life?NextA Closer Look at the Hello World Application

Last updated 5 years ago

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这里我们介绍如何在macOS环境下编写程序。如果过程中你遇到了困难可以参考

Checklist

在开始之前,请检查:

  1. The Java SE Development Kit 8 (JDK 8)

    下载地址,我们使用的是JDK 8。如果你遇到问题可以参考

  2. 文本编辑器 任何的文本编辑器都可以,比如vi

HelloWorld

我们的第一个程序是简单的输出Hello world!。请按照以下步骤:

  1. 创建源文件

源文件包含使用Java语言编写的源代码。你可以使用文本编辑器创建和修改源代码。创建一个名为HelloWorldApp.java的文件,文件内容是:

/**
 * The HelloWorldApp class implements an application that
 * simply prints "Hello World!" to standard output.
 */
class HelloWorldApp {
    public static void main(String[] args) {
        System.out.println("Hello World!"); // Display the string.
    }
}

注意编译器和启动器都是大小写敏感的,HelloWorldApp和helloworldapp是不一样的

  1. 将源文件编译成.class文件

Java编译器javac会将你的源代码翻译成Java虚拟机可以理解的指令。这些包含在.class文件中的指令我们称之为bytecodes。

  • 打开terminal(终端)将当前的目录切换到.java源文件所在目录。比如你的源文件在/tmp/examples/java,就输入cd /tmp/examples/java然后按Return(回车键)

  • 输入javac HelloWorldApp.java命令然后按Return。编译器将生成一个bytecode文件HelloWorldApp.class。现在你会在当前目录下看到两个文件HelloWorldApp.java和HelloWorldApp.class

  • 运行程序

Java应用launcher tool (java)使用Java虚拟机来运行你的程序。在当面目录直接输入java HelloWorldApp

Common Problems (and Their Solutions).
Java SE Downloads
installation instructions