java - Hello World 上出现 NoClassDefFoundError

Question

我正在尝试运行一个非常简单的程序并遇到错误。我制作了一个非常简单的 helloworld java 程序，但无法从 Mac 上的终端运行它。我已检查以确保类路径设置正确，但我很困惑为什么它没有运行。

这是程序:

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

这是终端命令:

Last login: Thu May  2 12:01:50 on ttys000
172-26-125-179:~ rohan$ cd /Users/rohan/Desktop 
172-26-125-179:Desktop rohan$ ls
Hello.java
172-26-125-179:Desktop rohan$ echo $CLASSPATH

172-26-125-179:Desktop rohan$ export CLASSPATH=/Users/rohan/Desktop
172-26-125-179:Desktop rohan$ echo $CLASSPATH
/Users/rohan/Desktop
172-26-125-179:Desktop rohan$ java Hello.java
Exception in thread "main" java.lang.NoClassDefFoundError: Hello/java
Caused by: java.lang.ClassNotFoundException: Hello.java
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
172-26-125-179:Desktop rohan$ 

任何想法将不胜感激! 更新忽略之前的情况，这是对我的问题的更好的看法:

Last login: Thu May  2 13:05:17 on ttys000
172-26-125-179:~ rohan$ cd /Users/rohan/Dropbox/Current/ds/lab6 
172-26-125-179:lab6 rohan$ ls
Hello.java
172-26-125-179:lab6 rohan$ cat Hello.java
public class Hello {
    public static void main(String[] args) {
        System.out.println("hi");
    }
}
172-26-125-179:lab6 rohan$ echo $CLASSPATH

172-26-125-179:lab6 rohan$ export CLASSPATH=/Users/rohan/Dropbox/Current/ds/lab6 
172-26-125-179:lab6 rohan$ echo $CLASSPATH
/Users/rohan/Dropbox/Current/ds/lab6
172-26-125-179:lab6 rohan$ javac Hello.java
172-26-125-179:lab6 rohan$ java Hello.class
Exception in thread "main" java.lang.NoClassDefFoundError: Hello/class
Caused by: java.lang.ClassNotFoundException: Hello.class
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
172-26-125-179:lab6 rohan$ 

Answer 1

尝试:

$ javac Hello.java

$ java 你好