force casting on null pointer

public class Test {
    public static void main(String[] ARGSTRING) {
        dummy();
        System.out.println("hello");
    }
    public static void dummy() {
        String a = (String)null;
        if(a instanceof String ) {
            System.out.println("String");
        }
        else {
            System.out.println("false");
        }
        System.out.println(a.split(".")[0].hashCode());

    }
}

=========================================================================

false

Exception in thread "main" java.lang.NullPointerException

at Test.dummy(Test.java:15)

at Test.main(Test.java:4)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

at java.lang.reflect.Method.invoke(Method.java:483)

at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)

Process finished with exit code 1