java batch modify file name

As a handsome (hard to force) of the student leaders, closely serving the people, this is not, after collecting the required photo file name + student number as required Student ID + name change

The fundamental difference between humans and animals is whether the use of tools, use the File class java batch operation, as follows:

Import java.io.File;
 / ** 
 * @author Pandas 
 * @date 2020/3/30 15:32 
 * @Version 1.0 
 * file name is: Wang sledgehammer _171060001.jpg 
 * want to convert: 171060001_ king sledgehammer .jpg 
 * / 
public  class FileDo {
     public  static  void main (String [] args) { 
        String dirName = "D: / photo / class photo *" ; 
        File dir = new new File (dirName); 
        File [] filesList = dir.listFiles ();
         // If the directory path exists and indeed 
        IF (dir.exists () && dir.isDirectory ()) {
             for(File File: filesList) {
                 // If the file in .jpg format 
                IF ... "." (File.isFile () && file.getName () substring (file.getName () lastIndexOf ()) the equals ( "JPG. " )) { 
                    String fileName = file.getName (); 
                    String name = fileName.substring (0, fileName.lastIndexOf (" _ " )); 
                    String Number = fileName.substring (fileName.indexOf (" _ ") +. 1, fileName.lastIndexOf ( "." ));
                     // rename the file name to be defined here as absolute virtual path 
                    file dest = new new file (dirName + "/"+number+"_"+name+".jpg" );
                    file.renameTo ();
                }
            }
        }
    }
}

Conventionally doc oriented programming:

The official document: https://docs.oracle.com/javase/8/docs/api/

Speaking: http://www.matools.com/api/java8