Question

用记事本写好java的源程序以后要怎样编译？？？

我在记事本里写入了这些内容：
public class HelloJava{
public static void main(String arg[]){
System.out.println("HI,java!");
}
}

然后我把记事本的名字（包括后缀）改为HelloJava.java

之后我就不知道要怎样做了。
书里说要在DOC下输入javac看看是不是有一行：
Usage: javac <options> <source files>
where possible options include:
-g Generate all debugging info
-g:none Generate no debugging info
-g:{lines,vars,source} Generate only some debugging info
-nowarn Generate no warnings
-verbose Output messages about what the compiler is doing
-deprecation Output source locations where deprecated APIs are u
sed
-classpath <path> Specify where to find user class files
-cp <path> Specify where to find user class files
-sourcepath <path> Specify where to find input source files
-bootclasspath <path> Override location of bootstrap class files
-extdirs <dirs> Override location of installed extensions
-endorseddirs <dirs> Override location of endorsed standards path
-d <directory> Specify where to place generated class files
-encoding <encoding> Specify character encoding used by source files
-source <release> Provide source compatibility with specified release

-target <release> Generate class files for specific VM version
-version Version information
-help Print a synopsis of standard options
-X Print a synopsis of nonstandard options
-J<flag> Pass <flag> directly to the runtime system
可是我的输入javac以后却写着：
'javac'不是内部或外部命令，等等
我要怎么办啊？？？？急急急

Answer 1

假设你的JDK安装路径是c:\jdk1.4.1
则设置环境变量（在我的电脑（右键单击）->属性->高级->环境变量）
名称: PATH
值:c:\jdk1.4.1\bin

不用重启电脑，只要设置完后重新打开DOS窗口

Answer 2

那是因为你的环境变量没有设置好
classpath; .;C:\jdk1.5.0_06\lib\tools.jar;C:\jdk1.5.0_06\lib\dt.jar;

path: C:\jdk1.5.0_06\bin;
再重起一下需要的话