INT-3696: Use StringBuilder in FtpFileInfo

JIRA: https://jira.spring.io/browse/INT-3696

spring-integration-ftp/src/main/java/org/springframework/integration/ftp/session/FtpFileInfo.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2011 the original author or authors.
+ * Copyright 2002-2015 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,13 +17,14 @@
 package org.springframework.integration.ftp.session;
 
 import org.apache.commons.net.ftp.FTPFile;
+
 import org.springframework.integration.file.remote.AbstractFileInfo;
 import org.springframework.integration.file.remote.FileInfo;
 import org.springframework.util.Assert;
 
 /**
  * A {@link FileInfo} implementation for FTP/FTPS.
- * 
+ *
  * @author Gary Russell
  * @since 2.1
  */
@@ -36,28 +37,34 @@ public class FtpFileInfo extends AbstractFileInfo<FTPFile> {
 		this.ftpFile = ftpFile;
 	}
 
+	@Override
 	public boolean isDirectory() {
 		return this.ftpFile.isDirectory();
 	}
 
+	@Override
 	public boolean isLink() {
 		return this.ftpFile.isSymbolicLink();
 	}
 
+	@Override
 	public long getSize() {
 		return this.ftpFile.getSize();
 	}
 
+	@Override
 	public long getModified() {
 		return this.ftpFile.getTimestamp().getTimeInMillis();
 	}
 
+	@Override
 	public String getFilename() {
 		return this.ftpFile.getName();
 	}
 
+	@Override
 	public String getPermissions() {
-		StringBuffer sb = new StringBuffer();
+		StringBuilder sb = new StringBuilder();
 		if (this.ftpFile.isDirectory()) {
 			sb.append("d");
 		} else if (this.ftpFile.isSymbolicLink()) {
@@ -113,6 +120,7 @@ public class FtpFileInfo extends AbstractFileInfo<FTPFile> {
 		return sb.toString();
 	}
 
+	@Override
 	public FTPFile getFileInfo() {
 		return this.ftpFile;
 	}