A program without class

A.java

/*
In Java 8 this program prints

java.lang.Throwable
	at A.printStackTrace(A.java:8)
	at A.<clinit>(A.java:5)
	at java.lang.Class.forName0(Native Method)

Note: <clinit> is the static initializer method for interface A
 */
public interface A {
    int a = printStackTrace();

    static int printStackTrace() {
        new Throwable().printStackTrace();
        return 0;
    }

    public static void main(String[] args) {

    }
}