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FileExtension.java

public enum FileExtension {

    JAVA(".java"),
    TEXT(".txt"),
    SQL(".sql"),
    FEATURE(".feature"),
    EXCEL(".xls");

    private String fileExtension;
    FileExtension(String fileExtension) {
        this.fileExtension = fileExtension;
    }

    public String getFileExtension() {
        return fileExtension;
    }

}

FileFinder.java

import java.io.File;
import java.util.ArrayList;
import java.util.List;

public class FileFinder {

    private String path;
    private boolean fileFound;
    private List<File> allFiles;
    private File fileToSearch;
    private FileFinder(String path) {
        this.path = path;
        allFiles = new ArrayList<>();
    }

    public static FileFinder fileFinder(String rootPath) {
        return new FileFinder(rootPath);
    }

    public static FileFinder fileFinder() {
        return new FileFinder(System.getProperty("user.dir"));
    }

    public List<File> find(FileExtension fileExtension) {
        collectFiles(new File(path),fileExtension.getFileExtension());
        return allFiles;
    }

    public File find(String fileName, FileExtension fileExtension) {
        collectFile(new File(path),fileName,fileExtension.getFileExtension());
        return fileToSearch;
    }

    private void collectFiles(File rootFile, String fileExtensionToSearch) {
        if(rootFile.exists() && rootFile.isDirectory()) {
            File[] files = rootFile.listFiles();
            assert files != null;
            for(File file : files) {
                if(!file.isDirectory()) {
                    fileFound = file.getName().endsWith(fileExtensionToSearch);
                    if(fileFound) {
                        allFiles.add(file);
                    }
                } else {
                   collectFiles(file,fileExtensionToSearch);
                }
            }
        }
    }

    private void collectFile(File rootFile, String fileName, String fileExtensionToSearch) {
        if(rootFile.exists() && rootFile.isDirectory()) {
            File[] files = rootFile.listFiles();
            assert files != null;
            for(File file : files) {
                if(!file.isDirectory()) {
                    fileFound = file.getName().contains(fileName) && file.getName().endsWith(fileExtensionToSearch);
                    if(fileFound) {
                        fileToSearch = file;
                        break;
                    }
                } else {
                    collectFile(file,fileName,fileExtensionToSearch);
                }
            }
        }
    }
}