Fix problematic chars in javadoc

Java 11 complains about unescaped ">" characters in javadocs. Also fixed some
compiler complaints about javadoc in StringFunctionUtils.

modules/rank-eval/src/test/java/org/elasticsearch/index/rankeval/ExpectedReciprocalRankTests.java

@@ -69,7 +69,7 @@ public class ExpectedReciprocalRankTests extends ESTestCase {
      * 4    | 1         | 0.03125   | 0.078125 | 0.00244140625 |
      * }</pre>
      *
-     * err => sum of last column
+     * err = sum of last column
      */
     public void testERRAt() {
         List<RatedDocument> rated = new ArrayList<>();
@@ -94,7 +94,7 @@ public class ExpectedReciprocalRankTests extends ESTestCase {
      * 4    | 1         | 0.03125   | 0.125    | 0.00390625 |
      * }</pre>
      *
-     * err => sum of last column
+     * err = sum of last column
      */
     public void testERRMissingRatings() {
         List<RatedDocument> rated = new ArrayList<>();

x-pack/plugin/sql/src/main/java/org/elasticsearch/xpack/sql/expression/function/scalar/string/StringFunctionUtils.java

@@ -6,9 +6,9 @@
 package org.elasticsearch.xpack.sql.expression.function.scalar.string;
 
 abstract class StringFunctionUtils {
-    
+
     /**
-     * Trims the trailing whitespace characters from the given String. Uses {@link java.lang.Character.isWhitespace(char)}
+     * Trims the trailing whitespace characters from the given String. Uses @link java.lang.Character.isWhitespace(char)
      * to determine if a character is whitespace or not.
      *
      * @param s       the original String
@@ -18,16 +18,16 @@ abstract class StringFunctionUtils {
         if (!hasLength(s)) {
             return s;
         }
-        
+
         StringBuilder sb = new StringBuilder(s);
         while (sb.length() > 0 && Character.isWhitespace(sb.charAt(sb.length() - 1))) {
             sb.deleteCharAt(sb.length() - 1);
         }
         return sb.toString();
     }
-    
+
     /**
-     * Trims the leading whitespace characters from the given String. Uses {@link java.lang.Character.isWhitespace(char)}
+     * Trims the leading whitespace characters from the given String. Uses @link java.lang.Character.isWhitespace(char)
      * to determine if a character is whitespace or not.
      *
      * @param s       the original String
@@ -37,7 +37,7 @@ abstract class StringFunctionUtils {
         if (!hasLength(s)) {
             return s;
         }
-        
+
         StringBuilder sb = new StringBuilder(s);
         while (sb.length() > 0 && Character.isWhitespace(sb.charAt(0))) {
             sb.deleteCharAt(0);