Java帮助：为什么我不能访问当前主方法文件之外的类中声明的静态方法

Question

Following the JavaDocs tutorial for SAX: The method usage() is not recognised from the main method. As far as I know it should be accessible as the methods are declared as static and exist within the same package as the main method.

public class Main {
    public static void main(String args[]){
        String filename = null;

//Checks to see if commnad line arguments are present
        for (int i = 0; i < args.length; i++) {
            filename = args[i];
            if (i != args.length - 1) {
                usage();
            }
        }

        if (filename == null) {
            usage();
        } 

//Defined in the same package as the main method
    public class SAXLocalNameCount extends DefaultHandler{
        private Hashtable tags;

        public void startDocument() throws SAXException{
            tags = new Hashtable();
        }

//The problem method    
    private static void usage() {
       System.err.println("Usage: SAXLocalNameCount <file.xml>");
       System.err.println("       -usage or -help = this message");
       System.exit(1);
    }
}

Answer 1

usage() appears to be a member of the SAXLocalNameCount class, not the Main class. Despite the indentation.

Answer 2

The usage method as is defined now can only be used from inside another static method or static code block of SAXLocalNameCount class.

You can:

1. Move the static main method inside the SAXLocalNameCount class and out of the Main class.
2. Change the visibility of usage method to public and than use it from the Main class -> static main method.