8203442: String::transform

Reviewed-by: smarks, sherman, alanb, darcy, forax, rriggs, scolebourne, dholmes, plevart

src/java.base/share/classes/java/lang/String.java

@@ -37,6 +37,7 @@ import java.util.Locale;
 import java.util.Objects;
 import java.util.Spliterator;
 import java.util.StringJoiner;
+import java.util.function.Function;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 import java.util.regex.PatternSyntaxException;
@@ -2972,6 +2973,25 @@ public final class String
         return indent(indent > n ? Integer.MIN_VALUE : indent, true);
     }
 
+    /**
+     * This method allows the application of a function to {@code this}
+     * string. The function should expect a single String argument
+     * and produce an {@code R} result.
+     *
+     * @param f    functional interface to a apply
+     *
+     * @param <R>  class of the result
+     *
+     * @return     the result of applying the function to this string
+     *
+     * @see java.util.function.Function
+     *
+     * @since 12
+     */
+    public <R> R transform(Function<? super String, ? extends R> f) {
+        return f.apply(this);
+    }
+
     /**
      * This object (which is already a string!) is itself returned.
      *