java FileWriter 追加文件及文件改名

import java.io.File;import java.io.FileWriter;import java.io.IOException;public class FileWriterUtil {    /**     * 追加文件：使用FileWriter     */    public static void appendMethod(String fileName, String content) {        try {            //打开一个写文件器，构造函数中的第二个参数true表示以追加形式写文件            FileWriter writer = new FileWriter(fileName, true);            writer.write(content);            writer.close();        } catch (IOException e) {            e.printStackTrace();        }    }    /**     * 修改文件名     * @param oldFilePath     * @param newFileName     */    public static void reNameLogFile(String oldFilePath,String newFileName){        File f=new File(oldFilePath);        String c=f.getParent();//        File mm=new File(c + File.pathSeparator + newFileName + "_" + CommonUtil.getCurrTimeForString());        File mm=new File(c + "/" + newFileName + "_" + CommonUtil.getBeforeDateStr());        if(f.renameTo(mm)){            System.out.println("修改文件名成功!");        }else{            System.out.println("修改文件名失败");        }    }    public static void main(String[] args) {        String fileName = "/Users/qin/Downloads/callLog.txt";        String content = "new append!";        FileWriterUtil.appendMethod(fileName, content);        FileWriterUtil.appendMethod(fileName, "append end. \n");        FileWriterUtil.reNameLogFile("/Users/qin/Downloads/callLog.txt","rayda");    }}