[benchmark] Add benchmarks suggested by Radek Hubner

Author: adamretter

exist-core-jmh/src/main/java/org/exist/xquery/utils/StringJoinBenchmark.java

@@ -89,6 +89,21 @@ public StringBuilder forApproach(/*final BuilderState builderState*/) {
         return builder;
     }
 
+    @Benchmark
+    public StringBuilder forApproachRadek(/*final BuilderState builderState*/) {
+//        final StringBuilder builder = builderState.builder;
+        final StringBuilder builder = new StringBuilder();
+
+        for (int i = 0; i < strings.size(); i++) {
+            builder.append(strings.get(i));
+            builder.append(", ");
+        }
+
+        builder.substring(0, builder.length() - 3);
+
+        return builder;
+    }
+
     @Benchmark
     public StringBuilder forEachApproach(/*final BuilderState builderState*/) {
 //        final StringBuilder builder = builderState.builder;
@@ -106,6 +121,22 @@ public StringBuilder forEachApproach(/*final BuilderState builderState*/) {
         return builder;
     }
 
+    @Benchmark
+    public StringBuilder forEachApproachRadek(/*final BuilderState builderState*/) {
+//        final StringBuilder builder = builderState.builder;
+        final StringBuilder builder = new StringBuilder();
+
+        boolean firstArgument = true;
+        for (final String str : strings) {
+            builder.append(str);
+            builder.append(", ");
+        }
+
+        builder.substring(0, builder.length() - 3);
+
+        return builder;
+    }
+
     @Benchmark
     public String jdkApproach() {
         return String.join(", ", strings);