用java批量重命名文件

import java.io.File;
public class FileRename {

    public static void main(String[] args) {
        String dir = "F:\\JAVA\\hibernate\\";    //选择要批量更改文件的文件夹，记得后面要加上\\表示文件夹下面的文件
        File file = new File(dir);
        String fileName[] = file.list();
        int number = fileName.length;        //获取文件数量
        File newFile[] = new File[number];    

        System.out.println("number = " + number);
        for(int i=0; i<number; i++) {
            System.out.println("第"+(i+1)+"个文件名" + ":" + fileName[i]);    //查看所有文件
            newFile[i] = new File(dir+fileName[i]);
        }
        System.out.println("============分割线=============");
        for(int i=0; i<number;i++){
            String fn = fileName[i];
            String newFileName = fn.substring(0, 3)+fn.substring(22);    //根据原来文件名来更改，用substring(begin,end)来截取字符串
            System.out.println(newFileName);
            boolean flag = newFile[number - (i+1)].renameTo(new File(dir + newFileName+".avi"));
            
            if(flag){
                System.out.println("重命名成功！"+":"+newFileName);
                System.out.println("重命名成功"+(i+1));
            } else {
                System.out.println("失败");
            }
        }
    }
    
}