Github user andyklimczak commented on a diff in the pull request: https://github.com/apache/commons-lang/pull/223#discussion_r94200421 --- Diff: src/main/java/org/apache/commons/lang3/StringUtils.java --- @@ -7193,6 +7193,45 @@ public static boolean isAllUpperCase(final CharSequence cs) { return true; } + /** + * <p>Checks if the CharSequence contains mixed casing of both uppercase and lowercase characters.</p> + * + * <p>{@code null} will return {@code false}. + * An empty String (length()=0) will return {@code false}.</p> + * + * <pre> + * StringUtils.isMixedCase(null) = false + * StringUtils.isMixedCase("") = false + * StringUtils.isMixedCase("aBc") = true + * StringUtils.isMixedCase("ABC") = false + * StringUtils.isMixedCase("abc") = false + * StringUtils.isMixedCase("A c") = false + * StringUtils.isMixedCase("A1c") = false + * StringUtils.isMixedCase("a/C") = false + * </pre> + * + * @param cs the CharSequence to check, may be null + * @return {@code true} if contains both uppercase and lowercase characters, and is non-null + */ + public static boolean isMixedCase(final CharSequence cs) { + if (cs == null || isEmpty(cs)) { + return false; + } + boolean containsUppercase = false; + boolean containsLowercase = false; + final int sz = cs.length(); + for (int i = 0; i < sz; i++) { --- End diff -- Almost, because consider the string "aB\n": It does contain a lowercase, then an uppercase, but it also contains the character '\n', which is a neither lower or uppercase. Breaking early would miss this case.
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