Remove reference of java 9 types:

Author: fluentfuture

mug-safesql/src/main/java/com/google/mu/safesql/ResultMapper.java

@@ -191,11 +191,12 @@ static Set<String> getCanonicalColumnNames(ResultSetMetaData metadata)
   private static String getNameForSql(Parameter param) {
     SqlName sqlName = param.getAnnotation(SqlName.class);
     if (sqlName != null) {
+      String name = sqlName.value().trim();
       checkArgument(
-          !sqlName.value().isBlank(),
+          name.length() > 0,
           "@SqlName defined in %s shouldn't be empty or blank: %s",
           param.getDeclaringExecutable().getDeclaringClass(), param);
-      return sqlName.value().trim();
+      return name;
     }
     String paramName = param.getName();
     boolean noRealName =

mug/src/main/java/com/google/mu/util/CharPredicate.java

@@ -231,7 +231,7 @@ default boolean matchesNoneOf(CharSequence sequence) {
    * @since 9.0
    */
   default boolean isPrefixOf(CharSequence sequence) {
-    return !sequence.isEmpty() && test(sequence.charAt(0));
+    return sequence.length() > 0 && test(sequence.charAt(0));
   }
 
   /**
@@ -240,6 +240,7 @@ default boolean isPrefixOf(CharSequence sequence) {
    * @since 9.0
    */
   default boolean isSuffixOf(CharSequence sequence) {
-    return !sequence.isEmpty() && test(sequence.charAt(sequence.length() - 1));
+    int len = sequence.length();
+    return len > 0 && test(sequence.charAt(len - 1));
   }
 }