### Question:
JavaIdentifierUtils { public static boolean isValidClassName(String className) { if (!className.contains(".")) { return className.matches("[A-Z][A-Za-z\\$]+"); } else { String packageName = getPackageName(className); return isValidClassName(className.substring(packageName.length() + 1, className.length())); } }  static String getJavaClassSimpleName(String javaClassName); static boolean isInnerClass(String javaClassName); static boolean isValidClassName(String className); static int getJavaClassNestingLevel(String javaClassName); static boolean isValidConstantName(String fieldName); static String getPackageName(String javaClassName); static boolean isJavaCoreClass(String javaClassName); static boolean hasSuperclassOrImplementsInterface(Class<?> javaClass, String superJavaClassOrInterfaceName); static Set<String> removeInnerClassesAndInvalidClassNames(Set<String> javaClassNames); static Set<String> javaClassNamesToPackages(Set<String> javaClassNames); static Set<String> removeJavaCoreClassNames(Set<String> javaClassNames);  }### Answer:
@Test public void isValidClassName() { assertTrue(JavaIdentifierUtils.isValidClassName("BlaCamelCase")); assertTrue(JavaIdentifierUtils.isValidClassName("haha.dummy.Bla$Test")); assertFalse(JavaIdentifierUtils.isValidClassName("test.$")); assertFalse(JavaIdentifierUtils.isValidClassName("Bla.$")); assertFalse(JavaIdentifierUtils.isValidClassName("test.Bla_haha")); assertFalse(JavaIdentifierUtils.isValidClassName("test.0Bla")); }