纯手动构建项目

We want to separate the source from the generated files, so our java source files will be in src folder. All generated files should be under build, and there splitted into several subdirectories for the individual steps: classes for our compiled files and jar for our own JAR-file.

We have to create only the src directory. (Because I am working on Windows, here is the win-syntax - translate to your shell):

md src

The following simple Java class just prints a fixed message out to STDOUT, so just write this code into src\oata\HelloWorld.java.

package oata;

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello World");
    }
}

Now just try to compile and run that:

md build\classes           //创建目录
javac -sourcepath src -d build\classes src\oata\HelloWorld.java
//编译
java -cp build\classes oata.HelloWorld   //执行class文件

which will result in
Hello World

====================================================
Creating a jar-file is not very difficult. But creating a startable jar-file needs more steps: create a manifest-file containing the start class, creating the target directory and archiving the files.

echo Main-Class: oata.HelloWorld>myManifest   //创建文件
md build\jar
jar cfm build\jar\HelloWorld.jar myManifest -C build\classes .
//将文件内容添加到jar包META-INF\MANIFEST.MF中
java -jar build\jar\HelloWorld.jar  //执行jar文件

Note: Do not have blanks around the >-sign in the echo Main-Class instruction because it would falsify it！