批量重命名一个文件夹的文件，例如：img下有600张图片，对其重名

import java.io.File;
import java.util.ArrayList;
import java.util.Arrays;

public class FileUtilDeal {
public static void main(String[] args) {
//File file = new File("E:\\极草\\img\\F20150603-1638459781.jpg");
//fileRename(file);
String [] fileName = getFileName("E:\\极草\\img");  // img文件夹下所有的文件名数组
ArrayList<String> listFileName = new ArrayList<String>();
getAllFileName("E:\\极草\\img",listFileName);
for(String name:listFileName)
{
fileRename(name);
}
}

public static void fileRename(String fileName){
File files = new File("E:\\极草\\img\\"+fileName);
String filePath = files.getPath();
System.out.println(filePath);
if(files.exists()){
files.renameTo(new File("E:\\极草\\img\\"+add000(fileName)+fileName));
}
}

public static void getAllFileName(String path,ArrayList<String> fileName)
{
File file = new File(path);
File [] files = file.listFiles();
String [] names = file.list();
if(names != null)
fileName.addAll(Arrays.asList(names));
for(File a:files)
{
if(a.isDirectory())
{
getAllFileName(a.getAbsolutePath(),fileName);
}
}
}
//
public static String [] getFileName(String path)
{
File file = new File(path);
String [] fileName = file.list();
return fileName;
}
//保证文件名的长度为30个字符
public static String  add000(String fileName){
String prefix=fileName.substring(fileName.lastIndexOf(".")+1);
int dot = fileName.lastIndexOf('.');
String f = fileName.substring(0, dot);
int _len = 30 - f.length();
StringBuffer buf = new StringBuffer();
for (int i = 0; i < _len; i++) {
buf.append("0");
}
return buf.toString();
}
}