### Question:
ClassHelper { public static boolean isStringClass (@Nullable final Class <?> aClass) { if (aClass == null) return false; return CharSequence.class.isAssignableFrom (aClass); } private  ClassHelper(); static boolean isPublicClass(@Nullable final Class <?> aClass); static boolean isInstancableClass(@Nullable final Class <?> aClass); static boolean isPublic(@Nullable final Class <?> aClass); static boolean isInterface(@Nullable final Class <?> aClass); static boolean isAnnotationClass(@Nullable final Class <?> aClass); static boolean isEnumClass(@Nullable final Class <?> aClass); static boolean isAbstractClass(@Nullable final Class <?> aClass); static boolean isArrayClass(@Nullable final Class <?> aClass); static boolean isPrimitiveType(@Nullable final Class <?> aClass); static boolean isPrimitiveWrapperType(@Nullable final Class <?> aClass); @Nullable static Class <?> getPrimitiveWrapperClass(@Nullable final Class <?> aClass); @Nullable static Class <?> getPrimitiveClass(@Nullable final Class <?> aClass); @Nonnull @ReturnsMutableCopy static ICommonsSet <Class <?>> getAllPrimitiveClasses(); @Nonnull @ReturnsMutableCopy static ICommonsSet <Class <?>> getAllPrimitiveWrapperClasses(); static boolean isStringClass(@Nullable final Class <?> aClass); static boolean isCharacterClass(@Nullable final Class <?> aClass); static boolean isBooleanClass(@Nullable final Class <?> aClass); static boolean isFloatingPointClass(@Nullable final Class <?> aClass); static boolean isIntegerClass(@Nullable final Class <?> aClass); static boolean areConvertibleClasses(@Nonnull final Class <?> aSrcClass, @Nonnull final Class <?> aDstClass); @Nullable static Class <?> getClass(@Nullable final Object aObject); @Nullable static String getClassName(@Nullable final Object aObject); @Nullable static String getClassLocalName(@Nullable final Object aObject); @Nullable static String getClassLocalName(@Nullable final Class <?> aClass); @Nullable static String getClassLocalName(@Nullable final String sClassName); @Nullable static String getClassPackageName(@Nullable final Object aObject); @Nullable static String getClassPackageName(@Nullable final Class <?> aClass); @Nullable static String getClassPackageName(@Nullable final String sClassName); @Nonnull @Nonempty static String getSafeClassName(@Nullable final Object aObject); @Nullable static String getDirectoryFromPackage(@Nullable final Package aPackage); @Nullable static String getDirectoryFromPackage(@Nullable final String sPackage); @Nullable static String getPathFromClass(@Nullable final Class <?> aClass); @Nullable static String getPathFromClass(@Nullable final String sClassName); @Nullable static String getClassFromPath(@Nullable final String sPath); @Nonnull @Nonempty static String getObjectAddress(@Nullable final Object aObject); @Nullable static URL getResource(@Nonnull final Class <?> aClass, @Nonnull @Nonempty final String sPath); @Nullable static InputStream getResourceAsStream(@Nonnull final Class <?> aClass, @Nonnull @Nonempty final String sPath);  }### Answer:
@Test public void testIsStringClass () { assertTrue (ClassHelper.isStringClass (String.class)); assertTrue (ClassHelper.isStringClass (StringBuilder.class)); assertFalse (ClassHelper.isStringClass (null)); assertFalse (ClassHelper.isStringClass (Integer.class)); assertFalse (ClassHelper.isStringClass (int.class)); }