native methods

[Igor Zeta]

Why calling a native method like this result in a runtime error?

public static native void amethod()
public static void main(String [] args){
amethod();
}

Maybe we have to load a library?
Then why in the StrictMath class there's code like this?

    public static long round(double a) {
return (long)floor(a + 0.5d);
    }
    public static native double floor(double a);

the class's comment states that all the algorithm gives the same
result as certain published algorithms.

/**These
* algorithms are available from the well-known network library
* <code>netlib</code> as the package "Freely Distributable
* Math Library" (<code>fdlibm</code>
* The network library may be found on the World Wide Web at:
* <blockquote><pre>
* <a href="http://metalab.unc.edu/">http://metalab.unc.edu/</a>;
* </pre></blockquote>
* <p>
**/

When this Library is loaded if no code there declares something
like this?
[ February 17, 2003: Message edited by: Igor Zeta ]

[Dan Culache]

Is it a runtime error or a compile time error?
Does your code compile?
The first line needs a semicolon.

[Igor Zeta]

provided the semicolon this is
the resulting run-time error:

java.lang.UnsatisfiedLinkError: amethod
at provecocoon.NewSuper.amethod(Native Method)
at provecocoon.NewSuper.main(NewSuper.java:25)
Exception in thread "main"

[Dan Culache]

Sorry, I didn't read carefully. I thought you were trying to use a native method defined in the StrictMath class. I'm not familiar with the Java linkage process but I'm sure this is what you need to do, specify a library. I believe your method "amethod" should be part of a library which was built using the Java Native Interface.
see Java Native Interface