Exception in thread "main" java.lang.IllegalArgumentException: Source must not be null    at org.springframework.util.Assert.notNull(Assert.java:115)    at Test.getaVoid(Test.java:11)    at Test.main(Test.java:6)    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:497)    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)

import org.springframework.util.Assert;public class Test {    public static void main(String[] args) {        getaVoid();        System.out.println("hello");    }    private static void getaVoid() {        Assert.notNull(null, "Source must not be null");    }}