Program to demonstrate how to clean contents of a directory using Apache commons-io API in Java.  
package com.hubberspot.apache.commons.examples;
import java.io.File;
import java.io.IOException;
import org.apache.commons.io.FileUtils;
public class CleanDirectoryDemo {
    public static void main(String[] args) {
        // Create a File object and pass path of the directory
        // where files needs to be cleaned
        File file = new File("D:/files");
        // FileUtils class of org.apache.commons.io
        // has a method by name cleanDirectory() which takes in
        // the directory where files need to be 
        // cleaned.
        try {
            FileUtils.cleanDirectory(file);
        } catch (IOException e) {
            
            e.printStackTrace();
        }
    }
}