Java找不到方法main

Question

Im having trouble with a simple hello world program lol! Im hoping someone can shed some light on this.

So the error im receiving is the following:

$ javac Hello.java
$ java Hello
Exception in thread "main" java.lang.NoSuchMethodError: main

So by the error, I can see that it's obviously missing main, but it's there:

class Hello
{
  public static void main(String argv)
  {
    System.out.println("hello world");
  }
}

I'm on Mac OS/X if it's any help.

Answer 1

Problem is that your method does not take String array as a argument. Use following signature instead:

public static void main(String[] argv)

or

public static void main(String argv[])

Other valid option is:

public static void main(String ... argv)

In Java Language Specification this is told as follows:

The method main must be declared public, static, and void. It must specify a formal parameter (§8.4.1) whose declared type is array of String.

Answer 2

You forgot about [] in String[] argv or ... in String... argv . This array is used to store arguments used in command creating JVM for your class like

java Hello argument0 argument1 argument2` 

and so on.

Answer 3

Main method has signature that accepts String[] and you wrote String which is wrong,

Make it

public static void main(String[] argv)

or varargs

public static void main(String... argv)

Answer 4

你忘了放数组语法，你甚至可以按照JAVA 1.5使用varargs

public static void main(String... argv)

Answer 5

problem is with main signature, which should be

public static void main(String[] argv)

or could be

public static void main(String ... argv) // known as varargs

instead of public static void main(String argv) which is in your case

have a look at this

for varargs look

Answer 6

public static void main(String[] args)
public static void main(String... args)
public static void main(String args[])

Java programs start executing at the main method, which has the above method prototype

Answer 7

Your main method signature is wrong String instead of String []

use

public static void main(String[] argv)

or

public static void main(String... argv)

read here