solved critical "Performance - Method concatenates strings using + in a loop"

Author: wumpz

src/main/java/net/sf/jsqlparser/statement/replace/Replace.java

@@ -105,32 +105,33 @@ public void setUseValues(boolean useValues) {
 
 	@Override
 	public String toString() {
-		String sql = "REPLACE " + table;
+		StringBuilder sql = new StringBuilder();
+		sql.append("REPLACE ").append(table);
 
 		if (expressions != null && columns != null) {
 			// the SET col1=exp1, col2=exp2 case
-			sql += " SET ";
+			sql.append(" SET ");
 			// each element from expressions match up with a column from columns.
 			for (int i = 0, s = columns.size(); i < s; i++) {
-				sql += "" + columns.get(i) + "=" + expressions.get(i);
-				sql += (i < s - 1) ? ", " : "";
+				sql.append(columns.get(i)).append("=").append(expressions.get(i));
+				sql.append((i < s - 1) ? ", " : "");
 			}
 		} else if (columns != null) {
 			// the REPLACE mytab (col1, col2) [...] case
-			sql += " " + PlainSelect.getStringList(columns, true, true);
+			sql.append(" ").append(PlainSelect.getStringList(columns, true, true));
 		}
 
 		if (itemsList != null) {
 			// REPLACE mytab SELECT * FROM mytab2
 			// or VALUES ('as', ?, 565)
 
 			if (useValues) {
-				sql += " VALUES";
+				sql.append(" VALUES");
 			}
 
-			sql += " " + itemsList;
+			sql.append(" ").append(itemsList);
 		}
 
-		return sql;
+		return sql.toString();
 	}
 }

src/main/java/net/sf/jsqlparser/statement/select/PlainSelect.java

@@ -161,31 +161,41 @@ public void setGroupByColumnReferences(List<Expression> list) {
 
 	@Override
 	public String toString() {
-		String sql = "SELECT ";
-		sql += ((distinct != null) ? "" + distinct + " " : "");
-		sql += ((top != null) ? "" + top + " " : "");
-		sql += getStringList(selectItems);
+		StringBuilder sql = new StringBuilder("SELECT ");
+		if (distinct != null) {
+			sql.append(distinct).append(" ");
+		}
+		if (top != null) {
+			sql.append(top).append(" ");
+		}
+		sql.append(getStringList(selectItems));
 		if (fromItem != null) {
-			sql += " FROM " + fromItem;
+			sql.append(" FROM ").append(fromItem);
 			if (joins != null) {
 				Iterator<Join> it = joins.iterator();
 				while (it.hasNext()) {
 					Join join = it.next();
 					if (join.isSimple()) {
-						sql += ", " + join;
+						sql.append(", ").append(join);
 					} else {
-						sql += " " + join;
+						sql.append(" ").append(join);
 					}
 				}
 			}
 			// sql += getFormatedList(joins, "", false, false);
-			sql += ((where != null) ? " WHERE " + where : "");
-			sql += getFormatedList(groupByColumnReferences, "GROUP BY");
-			sql += ((having != null) ? " HAVING " + having : "");
-			sql += orderByToString(orderByElements);
-			sql += ((limit != null) ? limit + "" : "");
+			if (where != null) {
+				sql.append(" WHERE ").append(where);
+			}
+			sql.append(getFormatedList(groupByColumnReferences, "GROUP BY"));
+			if (having != null) {
+				sql.append(" HAVING ").append(having);
+			}
+			sql.append(orderByToString(orderByElements));
+			if (limit != null) {
+				sql.append(limit);
+			}
 		}
-		return sql;
+		return sql.toString();
 	}
 
 	public static String orderByToString(List<OrderByElement> orderByElements) {