null用于输出的时候的问题

public static void main( String[] args )
    {
        func(new String[]{null});
    }

    public static void func(String...args) {
        System.out.println("arg length = "+args.length);
    }

运行结果1

 

public static void main( String[] args )
    {
        func((String)null);
    }

    public static void func(String...args) {
        System.out.println("arg length = "+args.length);
    }

运行结果1

 

public static void main( String[] args )
    {
        func(null);
    }

    public static void func(String...args) {
        System.out.println("arg length = "+args.length);
    }

报错

 

public static void main( String[] args )
    {
        func(null,null);
    }
    public static void func(String...args) {
        System.out.println("arg length = "+args.length);
    }

运行结果为2