Use StatementBuilder.append(char) instead of append(String) where possible

h2/src/main/org/h2/command/dml/Insert.java

@@ -415,7 +415,7 @@ public class Insert extends Prepared implements ResultTarget {
         for (Column column : duplicateKeyAssignmentMap.keySet()) {
             buff.appendExceptFirst(", ");
             Expression ex = duplicateKeyAssignmentMap.get(column);
-            buff.append(column.getSQL()).append("=").append(ex.getSQL());
+            buff.append(column.getSQL()).append('=').append(ex.getSQL());
         }
         buff.append(" WHERE ");
         Index foundIndex = (Index) de.getSource();

h2/src/main/org/h2/command/dml/Select.java

@@ -1164,7 +1164,7 @@ public class Select extends Query {
                         buff.appendExceptFirst(",");
                         buff.append(c.getName());
                     }
-                    buff.append(") AS ").append(t.getSQL()).append("\n");
+                    buff.append(") AS ").append(t.getSQL()).append('\n');
                 }
             }
         }

h2/src/main/org/h2/expression/Function.java

@@ -2492,7 +2492,7 @@ public class Function extends Expression implements FunctionCall {
         StatementBuilder buff = new StatementBuilder(info.name);
         if (info.type == CASE) {
             if (args[0] != null) {
-                buff.append(" ").append(args[0].getSQL());
+                buff.append(' ').append(args[0].getSQL());
             }
             for (int i = 1, len = args.length - 1; i < len; i += 2) {
                 buff.append(" WHEN ").append(args[i].getSQL());

h2/src/tools/org/h2/jaqu/SQLDialect.java

@@ -98,12 +98,12 @@ public interface SQLDialect {
             buff.append(index.indexName);
             buff.append(" ON ");
             buff.append(table);
-            buff.append("(");
+            buff.append('(');
             for (String col : index.columnNames) {
                 buff.appendExceptFirst(", ");
                 buff.append(col);
             }
-            buff.append(")");
+            buff.append(')');
             return buff.toString();
         }