Get file extension in java

package com.candidjava.file;

import java.io.File;

public class FileExtension {
  public static void main(String[] args) {
    File file = new File("demo.txt");
    String name = file.getName();
    String fileExtension;
    if ((name.lastIndexOf(".") != -1) && (name.lastIndexOf(".")) != 0) {
      fileExtension = name.substring(name.lastIndexOf(".") + 1);
      System.out.println("File Extension is:" + fileExtension);
    } else {
      System.out.println("Invalid file format");
    }
  }
}