Example.java

import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
import java.util.stream.Collectors;
import org.apache.commons.io.FilenameUtils;

public class Test {

	static Set<String> get1(File root) {
		Set<String> names = new HashSet<>();
		for (File file : root.listFiles())
			if (FilenameUtils.isExtension(file.getPath(), Arrays.asList("jar", "war", "zip")))
				names.add(FilenameUtils.getBaseName(file.getPath()));
		return names;
	}

	static Set<String> get2(Path root) throws IOException {
		return Files.list(root).
			filter(path -> FilenameUtils.isExtension(path.toFile().getPath(), Arrays.asList("jar", "war", "zip"))).
			map(path -> FilenameUtils.getBaseName(path.toFile().getPath())).
			collect(Collectors.toSet());
	}

	public static void main(String[] args) throws IOException {
		System.err.println(get1(new File("lib")));
		System.err.println(get2(Paths.get("lib")));
	}
}