[Java] Efficiency improvements to display decoder.

Author: mjpt777

sbe-samples/src/main/resources/example-extension-schema.xml

@@ -65,7 +65,7 @@
         <group name="fuelFigures" id="10" dimensionType="groupSizeEncoding">
             <field name="speed" id="11" type="uint16"/>
             <field name="mpg" id="12" type="float"/>
-            <data name="usageDescription" id="200" type="varStringEncoding"/>
+            <data name="usageDescription" id="200" type="varAsciiEncoding"/>
         </group>
         <group name="performanceFigures" id="13" dimensionType="groupSizeEncoding">
             <field name="octaneRating" id="14" type="Ron"/>

sbe-samples/src/main/resources/example-schema.xml

@@ -61,7 +61,7 @@
         <group name="fuelFigures" id="10" dimensionType="groupSizeEncoding">
             <field name="speed" id="11" type="uint16"/>
             <field name="mpg" id="12" type="float"/>
-            <data name="usageDescription" id="200" type="varStringEncoding"/>
+            <data name="usageDescription" id="200" type="varAsciiEncoding"/>
         </group>
         <group name="performanceFigures" id="13" dimensionType="groupSizeEncoding">
             <field name="octaneRating" id="14" type="Ron"/>

sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/java/JavaGenerator.java

@@ -3203,6 +3203,7 @@ private void appendGroupInstanceDecoderDisplay(
         Separators.BEGIN_COMPOSITE.appendToGeneratedBuilder(sb, indent + INDENT, "builder");
         appendDecoderDisplay(sb, fields, groups, varData, indent + INDENT);
         Separators.END_COMPOSITE.appendToGeneratedBuilder(sb, indent + INDENT, "builder");
+        sb.append('\n');
         append(sb, indent, "    return builder;");
         append(sb, indent, "}");
     }
@@ -3383,7 +3384,7 @@ private void appendToString(final StringBuilder sb, final String indent)
         sb.append('\n');
         append(sb, indent, "public String toString()");
         append(sb, indent, "{");
-        append(sb, indent, "    return appendTo(new StringBuilder(100)).toString();");
+        append(sb, indent, "    return appendTo(new StringBuilder()).toString();");
         append(sb, indent, "}");
     }
 }

sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/java/JavaUtil.java

@@ -58,15 +58,15 @@ public enum Separators
         }
 
         /**
-         * Add separator to a generated StringBuilder
+         * Add separator to a generated append to a {@link StringBuilder}.
          *
          * @param builder     the code generation builder to which information should be added
          * @param indent      the current generated code indentation
          * @param builderName of the generated StringBuilder to which separator should be added
          */
         public void appendToGeneratedBuilder(final StringBuilder builder, final String indent, final String builderName)
         {
-            append(builder, indent, builderName + ".append('" + symbol + "');");
+            builder.append(indent).append(builderName).append(".append('").append(symbol).append("');").append('\n');
         }
 
         public String toString()