Improvement | Replace string concatenation with StringBuilder (#861)

* Avoid string concatenation in `StringBuilder.append()`

* Replace string concatenation w/ StringBuilder in loops

Author: simon04

src/main/java/com/microsoft/sqlserver/jdbc/IOBuffer.java

@@ -2108,8 +2108,8 @@ final void close() {
         //
         // Note: the log formatter itself timestamps what we write so we don't have
         // to do it again here.
-        logMsg.append(tcpSocket.getLocalAddress().toString() + ":" + tcpSocket.getLocalPort() + " SPID:" + spid + " "
-                + messageDetail + "\r\n");
+        logMsg.append(tcpSocket.getLocalAddress().toString()).append(":").append(tcpSocket.getLocalPort())
+                .append(" SPID:").append(spid).append(" ").append(messageDetail).append("\r\n");
 
         // Fill in the body of the log message, line by line, 16 bytes per line.
         int nBytesLogged = 0;
@@ -2295,7 +2295,7 @@ Socket findSocket(String hostName, int portNumber, int timeoutInMilliSeconds, bo
                 loggingString.append(". They are: ");
 
                 for (InetAddress inetAddr : inetAddrs) {
-                    loggingString.append(inetAddr.toString() + ";");
+                    loggingString.append(inetAddr.toString()).append(";");
                 }
 
                 logger.finer(loggingString.toString());

src/main/java/com/microsoft/sqlserver/jdbc/SQLServerBulkCopy.java

@@ -1450,7 +1450,7 @@ private String createInsertBulkCommand(TDSWriter tdsWriter) throws SQLServerExce
         StringBuilder bulkCmd = new StringBuilder();
         List<String> bulkOptions = new ArrayList<>();
         String endColumn = " , ";
-        bulkCmd.append("INSERT BULK " + destinationTableName + " (");
+        bulkCmd.append("INSERT BULK ").append(destinationTableName).append(" (");
 
         for (int i = 0; i < (columnMappings.size()); ++i) {
             if (i == columnMappings.size() - 1) {
@@ -1471,9 +1471,11 @@ private String createInsertBulkCommand(TDSWriter tdsWriter) throws SQLServerExce
             }
             if (colMapping.destinationColumnName.contains("]")) {
                 String escapedColumnName = colMapping.destinationColumnName.replaceAll("]", "]]");
-                bulkCmd.append("[" + escapedColumnName + "] " + destType + addCollate + endColumn);
+                bulkCmd.append("[").append(escapedColumnName).append("] ").append(destType).append(addCollate)
+                        .append(endColumn);
             } else {
-                bulkCmd.append("[" + colMapping.destinationColumnName + "] " + destType + addCollate + endColumn);
+                bulkCmd.append("[").append(colMapping.destinationColumnName).append("] ").append(destType)
+                        .append(addCollate).append(endColumn);
             }
         }
 

src/main/java/com/microsoft/sqlserver/jdbc/SQLServerDatabaseMetaData.java

@@ -521,17 +521,16 @@ public java.sql.ResultSet getTables(String catalog, String schema, String table,
         arguments[1] = schema;
         arguments[2] = catalog;
 
-        String tableTypes = null;
         if (types != null) {
-            tableTypes = "'";
+            final StringBuilder tableTypes = new StringBuilder("'");
             for (int i = 0; i < types.length; i++) {
                 if (i > 0)
-                    tableTypes += ",";
-                tableTypes += "''" + types[i] + "''";
+                    tableTypes.append(",");
+                tableTypes.append("''").append(types[i]).append("''");
             }
-            tableTypes += "'";
+            tableTypes.append("'");
+            arguments[3] = tableTypes.toString();
         }
-        arguments[3] = tableTypes;
         return getResultSetWithProvidedColumnNames(catalog, CallableHandles.SP_TABLES, arguments, getTablesColumnNames);
     }
 

src/main/java/com/microsoft/sqlserver/jdbc/SQLServerException.java

@@ -118,7 +118,7 @@ private void logException(Object o, String errText, boolean bStack) {
                     sb.append(aSt.toString());
                 Throwable t = this.getCause();
                 if (t != null) {
-                    sb.append("\n caused by " + t + "\n");
+                    sb.append("\n caused by ").append(t).append("\n");
                     StackTraceElement tst[] = t.getStackTrace();
                     for (StackTraceElement aTst : tst)
                         sb.append(aTst.toString());

src/main/java/com/microsoft/sqlserver/jdbc/SQLServerParameterMetaData.java

@@ -645,7 +645,7 @@ private void checkClosed() throws SQLServerException {
                     StringBuilder sbColumns = new StringBuilder();
 
                     for (MetaInfo mi : metaInfoList) {
-                        sbColumns = sbColumns.append(mi.fields + ",");
+                        sbColumns = sbColumns.append(mi.fields).append(",");
                     }
                     sbColumns.deleteCharAt(sbColumns.length() - 1);
 
@@ -660,9 +660,10 @@ private void checkClosed() throws SQLServerException {
                                     && metaInfoList.get(i).fields.equals(metaInfoList.get(i - 1).fields)) {
                                 continue;
                             }
-                            sbTablesAndJoins = sbTablesAndJoins.append(" LEFT JOIN " + metaInfoList.get(i).table
-                                    + " ON " + metaInfoList.get(i - 1).table + "." + metaInfoList.get(i - 1).fields
-                                    + "=" + metaInfoList.get(i).table + "." + metaInfoList.get(i).fields);
+                            sbTablesAndJoins = sbTablesAndJoins.append(" LEFT JOIN ").append(metaInfoList.get(i).table)
+                                    .append(" ON ").append(metaInfoList.get(i - 1).table).append(".")
+                                    .append(metaInfoList.get(i - 1).fields).append("=")
+                                    .append(metaInfoList.get(i).table).append(".").append(metaInfoList.get(i).fields);
                         }
                     }
 

src/main/java/com/microsoft/sqlserver/jdbc/SQLServerStatement.java

@@ -1012,29 +1012,28 @@ static String replaceParameterWithString(String str, char marker, String replace
      */
     static String replaceMarkerWithNull(String sql) {
         if (!sql.contains("'")) {
-            String retStr = replaceParameterWithString(sql, '?', "null");
-            return retStr;
+            return replaceParameterWithString(sql, '?', "null");
         } else {
             StringTokenizer st = new StringTokenizer(sql, "'", true);
             boolean beforeColon = true;
-            String retSql = "";
+            final StringBuilder retSql = new StringBuilder();
             while (st.hasMoreTokens()) {
                 String str = st.nextToken();
                 if (str.equals("'")) {
-                    retSql += "'";
+                    retSql.append("'");
                     beforeColon = !beforeColon;
                     continue;
                 }
                 if (beforeColon) {
                     String repStr = replaceParameterWithString(str, '?', "null");
-                    retSql += repStr;
+                    retSql.append(repStr);
                     continue;
                 } else {
-                    retSql += str;
+                    retSql.append(str);
                     continue;
                 }
             }
-            return retSql;
+            return retSql.toString();
         }
     }
 

src/main/java/com/microsoft/sqlserver/jdbc/Util.java

@@ -1044,19 +1044,19 @@ final String asEscapedString() {
         StringBuilder fullName = new StringBuilder(256);
 
         if (serverName.length() > 0)
-            fullName.append("[" + serverName + "].");
+            fullName.append("[").append(serverName).append("].");
 
         if (databaseName.length() > 0)
-            fullName.append("[" + databaseName + "].");
+            fullName.append("[").append(databaseName).append("].");
         else
             assert 0 == serverName.length();
 
         if (schemaName.length() > 0)
-            fullName.append("[" + schemaName + "].");
+            fullName.append("[").append(schemaName).append("].");
         else if (databaseName.length() > 0)
             fullName.append('.');
 
-        fullName.append("[" + objectName + "]");
+        fullName.append("[").append(objectName).append("]");
 
         return fullName.toString();
     }