// onjava/ProcessFiles.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
package onjava;
import java.io.*;
import java.nio.file.*;

public class ProcessFiles {
 public interface Strategy {
 void process(File file);
 }
 private Strategy strategy;
 private String ext;
 public ProcessFiles(Strategy strategy, String ext) {
 this.strategy = strategy;
 this.ext = ext;
 }
 public void start(String[] args) {
 try {
 if(args.length == 0)
 processDirectoryTree(new File("."));
 else
 for(String arg : args) {
 File fileArg = new File(arg);
 if(fileArg.isDirectory())
 processDirectoryTree(fileArg);
 else {
 // Allow user to leave off extension:
 if(!arg.endsWith("." + ext))
 arg += "." + ext;
 strategy.process(
 new File(arg).getCanonicalFile());
 }
 }
 } catch(IOException e) {
 throw new RuntimeException(e);
 }
 }
 public void
 processDirectoryTree(File root) throws IOException {
 PathMatcher matcher = FileSystems.getDefault()
 .getPathMatcher("glob:**/*.{" + ext + "}");
 Files.walk(root.toPath())
 .filter(matcher::matches)
 .forEach(p -> strategy.process(p.toFile()));
 }
}