resource_loader2.java

class ConcatPath implements Function<String,String> {
  private final String subPath;  

  private ConcatPath(String subPath){
    this.subPath = subPath;
  }

  @Override
  public String apply(String basePath){
    return FilenameUtils.concat(basePath,subPath);
  }
  
  public static ConcatPath with(String subPath){
    return new ConcatPath(subPath);
  }
}

public class FileCreator implements Function<String, File> {

  @Override
  public File apply(String path){
    File result = new File(path);
    return result;
  }

}

public class FileExistanceChecker implements Predicate<File> {

  @Override
  public boolean apply(File input){
    return input.exists();
  }

}

public class File {

  public static FileCreator createFromPath(){
    return new FileCreator();
  }

  public static FileExistanceChecker ifExists(){
    return new FileExistanceChecker();
  }

}