How do I check if a file exists?

Source:

import java.io.File;
 
public class FileExists {
   public static void main(String[] args) {
 
      String str = "/etc/hostname";
      File f = new File(str);
      if(f.exists()) { 
         System.out.println("File " + str + " exist.");
      }
   }
}

Output:

   $ java FileExists 
   File /etc/hostname exist.