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Multithread PDF manipulation

I'm writing a java program whose operation is summarized as follows:
The subfolder with the specified name is selected in the source
folder.
All the pdfs are taken and converted into txt files in
the target folder.
The name of an item is searched inside the
txt.
If the name is found then the pdf from source to target is
copied.
All the txt from the target folder are deleted, in this
way all the pdfs containing the searched word remain.
"It all works", the problem is that the txt files are not deleted from target and I can not understand why. Thanks in advance, best regards.
Launcher.java:
import java.lang.String;
import java.util.Scanner;
import java.io.File;
public class Launcher {
// campi
int status = 1;
static String source = "C:\\Users\\MyUser\\Desktop\\source\\";
static String target = "C:\\Users\\MyUser\\Desktop\\target\\";
public static void main(String [] args) {
// strings
String src = source;
String item = "";
// init
Scanner scan = new Scanner(System.in);
System.out.print("\nFornitore: ");
src += scan.nextLine().toUpperCase() + "\\";
System.out.print("Item: ");
item = scan.nextLine();
// notifier
Launcher launcher = new Launcher();
// threads
MakerThread maker = new MakerThread(launcher, src, target);
SearcherThread searcher = new SearcherThread(launcher, src, target, item);
CleanupThread cleaner = new CleanupThread(launcher, target);
// run
maker.start();
searcher.start();
cleaner.start();
}
}
MakerThread.java:
import java.io.File;
public class MakerThread extends Thread {
// campi
String src = "";
String target = "";
Launcher launcher;
// costruttore
public MakerThread(Launcher launcher, String src, String target) {
this.src = src;
this.target = target;
this.launcher = launcher;
}
// metodi
#Override
public void run() {
try{
synchronized (launcher) {
File folder = new File(this.src);
for (File f : folder.listFiles()) {
// spin-lock
while (launcher.status != 1){
launcher.wait();
}
if(f.isFile() && f.getName().endsWith("pdf")) {
System.out.println("PDF TROVATO: " + f.getName());
// input
String input = win_str(src + f.getName());
// output
String output = target;
output += f.getName().replaceAll(".pdf", ".txt");
output = win_str(output);
// command
String command = "cmd /C java -jar ./pdfbox-app-2.0.11.jar ExtractText ";
command += input + " " + output;
Process p1 = Runtime.getRuntime().exec(command);
p1.waitFor();
}
}
// set status, awake other threads
launcher.status = 2;
launcher.notifyAll();
}
}catch (Exception e) {
System.out.println("Exception: "+e.getMessage());
}
}
private String win_str(String str) {
return "\"" + str + "\"";
}
}
SearcherThread.java:
import java.io.File;
import java.io.BufferedReader;
import java.io.FileReader;
public class SearcherThread extends Thread {
// campi
String src = "";
String target = "";
String item = "";
Launcher launcher;
// costruttore
public SearcherThread(Launcher launcher, String src, String target, String item) {
this.target = target;
this.src = src;
this.item = item;
this.launcher = launcher;
}
// metodi
#Override
public void run() {
try{
synchronized (launcher) {
File folder = new File(this.target);
for(File f : folder.listFiles()) {
// spin-lock
while (launcher.status != 2){
launcher.wait();
}
if(f.isFile() && f.getName().endsWith("txt")) {
System.out.println("SEARCHING IN: " + f.getName());
// init
String line;
BufferedReader br = new BufferedReader(new FileReader(new File(target+f.getName())));
// txt search
while((line = br.readLine()) != null) {
if(line.contains(item)) {
System.out.println(" [" + item + "]" + " trovato in " + f.getName() + "\n");
// input
String pdf = f.getName().replaceAll(".txt", ".pdf");
String input = win_str(src+pdf);
// output
String output = win_str(target);
// command
String command = "cmd /C copy " + input + " " + output;
Process p1 = Runtime.getRuntime().exec(command);
p1.waitFor();
break;
}
}
}
}
// set status, awake other threads
launcher.status = 3;
launcher.notifyAll();
}
}catch (Exception e) {
System.out.println("Exception: "+e.getMessage());
}
}
private String win_str(String str) {
return "\"" + str + "\"";
}
}
CleanupThread.java:
import java.io.File;
public class CleanupThread extends Thread {
// campi
String target = "";
Launcher launcher;
// costruttore
public CleanupThread(Launcher launcher, String target) {
this.target = target;
this.launcher = launcher;
}
// metodi
#Override
public void run() {
try{
synchronized (launcher) {
File folder = new File(this.target);
for (File f : folder.listFiles()) {
// spin-lock
while (launcher.status != 3){
launcher.wait();
}
if(f.isFile() && f.getName().endsWith("txt")) {
System.out.println("CLEANING UP: " + f.getName());
// input
String input = win_str(target + f.getName());
// command
String command = "cmd /C del " + input;
Process p1 = Runtime.getRuntime().exec(command);
p1.waitFor();
}
}
// set status, awake other threads
launcher.status = 1;
launcher.notifyAll();
}
}catch (Exception e) {
System.out.println("Exception: "+e.getMessage());
}
}
private String win_str(String str) {
return "\"" + str + "\"";
}
}

How to read Java class def from .class file?

I am writing Java application and I want to write some simple plugin system. I want to have base class Plugin. Other classes extends Plugin, these files are in some other directory out of class path.
public class Plugin {
public Plugin() {
//code
}
public void proc() {
//code
}
}
and class loader:
public class PluginLoader {
private static final FilenameFilter filter = new FilenameFilter() {
#Override
public boolean accept(File dir, String name) {
return Pattern.matches("^.*[a-zA-Z]*[.]class$", name);
}
};
public static final String removeExtension(String str) {
if (str == null)
return null;
int pos = str.lastIndexOf(".");
if (pos == -1)
return str;
return str.substring(0, pos);
}
#SuppressWarnings("unchecked")
public static LinkedList<Plugin> loadEffects(String path) {
LinkedList<Plugin> result = new LinkedList<Plugin>();
Plugin instance = null;
File[] classesList = null;
System.out.println("Searching in " + path);
try {
File classDir = new File(path);
URL[] url = { classDir.toURI().toURL() };
URLClassLoader urlLoader = new URLClassLoader(url);
String filename;
classesList = classDir.listFiles(filter);
System.out.println(classesList.length + " class files found:");
for (File file : classesList) {
System.out.println("- " + file.getName());
}
for (File file : classesList) {
filename = removeExtension(file.getName());
if (filename.equals(".") || filename.equals("..") || filename.startsWith("."))
continue;
if (filename.equals("Plugin")) {
System.err.println("File name is Plugin");
continue;
}
System.out.println("Reading " + filename);
instance = (Plugin) urlLoader.findClass(filename).getConstructor().newInstance();
System.out.println("Adding: " + url + ", " + filename);
result.push(instance);
}
urlLoader.close();
} catch (Exception e) {
e.printStackTrace();
}
return result;
}
}
This code causes java.lang.NoClassDefFoundError: D:\test\PluginImpl/class (wrong name: test/PluginImpl). Plugin class is in D:\test.

You are calling File#getAbsolutePath() which will include the entire path and the drive letter (D:\). The class name stored in the class does not match with the class name you provided so Java throws an error.
Try calling findClass with just the class name and it should work

Delete all empty folders in Java

I'd like to write a function that deletes all empty folders, with the option to ignore certain file types (allowed file types are stored in the hashmap) and tell if it should look inside directories.
Calling:
HashMap<String, Boolean> allowedFileTypes = new HashMap<String, Boolean>();
allowedFileTypes.put("pdf", true);
deleteEmptyFolders("ABSOLUTE PATH", allowedFileTypes, true);
Function:
public static void deleteEmptyFolders(String folderPath, HashMap<String, Boolean> allowedFileTypes, boolean followDirectory) {
File targetFolder = new File(folderPath);
File[] allFiles = targetFolder.listFiles();
if (allFiles.length == 0)
targetFolder.delete();
else {
boolean importantFiles = false;
for (File file : allFiles) {
String fileType = "folder";
if (!file.isDirectory())
fileType = file.getName().substring(file.getName().lastIndexOf('.') + 1);
if (!importantFiles)
importantFiles = (allowedFileTypes.get(fileType) != null);
if (file.isDirectory() && followDirectory)
deleteEmptyFolders(file.getAbsolutePath(), allowedFileTypes, followDirectory);
}
// if there are no important files in the target folder
if (!importantFiles)
targetFolder.delete();
}
}
The problem is that nothing is happening, even though it looks through all folders till the end. Is this a good approach or am I missing something completely?

This piece of code recursively delete all the empty folders or directory:
public class DeleteEmptyDir {
private static final String FOLDER_LOCATION = "E:\\TEST";
private static boolean isFinished = false;
public static void main(String[] args) {
do {
isFinished = true;
replaceText(FOLDER_LOCATION);
} while (!isFinished);
}
private static void replaceText(String fileLocation) {
File folder = new File(fileLocation);
File[] listofFiles = folder.listFiles();
if (listofFiles.length == 0) {
System.out.println("Folder Name :: " + folder.getAbsolutePath() + " is deleted.");
folder.delete();
isFinished = false;
} else {
for (int j = 0; j < listofFiles.length; j++) {
File file = listofFiles[j];
if (file.isDirectory()) {
replaceText(file.getAbsolutePath());
}
}
}
}
}

You can use code to delete empty folders using Java.
public static long deleteFolder(String dir) {
File f = new File(dir);
String listFiles[] = f.list();
long totalSize = 0;
for (String file : listFiles) {
File folder = new File(dir + "/" + file);
if (folder.isDirectory()) {
totalSize += deleteFolder(folder.getAbsolutePath());
} else {
totalSize += folder.length();
}
}
if (totalSize ==0) {
f.delete();
}
return totalSize;
}

Shortest code I could come up with is following Java >=8 code:
Files.walk(Paths.get("/my/base/dir/"))
.sorted(Comparator.reverseOrder())
.map(Path::toFile)
.filter(File::isDirectory)
.forEach(File::delete);
Add a second (or more) filter statement with whatever clause you need to include/exclude certain folders. File::delete should not delete folders with contents.
Use at own risk.

Kotlin:
fun deleteAllEmptyDirectories(rootPath: Path): Collection<Path> =
mutableListOf<Path>()
.apply {
Files.walk(testPath)
.sorted { p1, p2 -> p2.count() - p1.count() }
.map { it.toFile() }
.filter { it.isDirectory }
.forEach {
if (it.listFiles().all { el -> el.isDirectory && contains(el.toPath()) }) {
val path = it.toPath()
add(path)
Files.delete(path)
}
}
}
Test:
private val testPath = Path.of("build", javaClass.simpleName, UUID.randomUUID().toString())
#Test
fun test() {
Files.createDirectory(testPath)
val dirWithTwoEmptySubdirs = Files.createDirectory(testPath.resolve("dirWithTwoEmptySubdirs"))
val dir1 = Files.createDirectory(dirWithTwoEmptySubdirs.resolve("dir1"))
val dir2 = Files.createDirectory(dirWithTwoEmptySubdirs.resolve("dir2"))
val dirWithOneDiffDir = Files.createDirectory(testPath.resolve("dirWithOneDiffDir"))
var emptyDir = Files.createDirectory(dirWithOneDiffDir.resolve("empty"))
val notEmptyDir = Files.createDirectory(dirWithOneDiffDir.resolve("notempty"))
Files.writeString(notEmptyDir.resolve("file.txt"), "asdf")
assertEquals(
setOf<Path>(dirWithTwoEmptySubdirs, dir1, dir2, emptyDir),
deleteAllEmptyDirectories(testPath).toSet()
)
}

After reading all answers and concluding that all of them have at least one problem I still had to write it myself:
import java.io.File;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
public class Temp {
public static void main(String[] args) {
final String path = "D:\\";
deleteEmpty(new File(path));
}
private static int deleteEmpty(File file) {
List<File> toBeDeleted = Arrays.stream(file.listFiles()).sorted() //
.filter(File::isDirectory) //
.filter(f -> f.listFiles().length == deleteEmpty(f)) //
.collect(Collectors.toList());
int size = toBeDeleted.size();
toBeDeleted.forEach(t -> {
final String path = t.getAbsolutePath();
final boolean delete = t.delete();
System.out.println("Deleting: \t" + delete + "\t" + path);
});
return size;
}
}

How to find out where a class originates from at runtime?

I'm having this weird issue where a class from some transitive dependency keeps showing up at runtime, shadowing a newer version of the class from the (correct) first level dependency, even though I thought I made sure that I excluded the older version from all other dependencies I declare (this is in a Maven/IntelliJ setup)
More specifically, at runtime the app fails with a NoClassDefFoundError, since during class loading a wrong version of the owning class is loaded, which has a field of a type that does not exist in newer versions of the library that class is defined in. To illustrate:
// lib.jar:wrong-version
class Owner {
private SomeType f;
}
// lib.jar:new-version
class Owner {
private OtherType f;
}
At runtime, the class loader finds a reference to the symbol Owner and attempts to load the version that has SomeType, which in return does not exist anymore. This is even though I excluded wrong-version where ever I could spot it.
I also ran mvn dependency:tree to see if the old version is still being pulled in somewhere, but it's not!
In order to further debug this, I was wondering if there is a way to find out where a class loader was reading a specific class from, i.e. which file? Is that possible? Or even better, build a list of origins where a certain symbol is defined, in case it's defined more than once?
Sorry if this is vague, but the problem is rather nebulous.

The following code will search the whole classpath for a particular class. With no arguments it will dump every class it finds and then you can pipe to grep or redirect to a file. It looks inside jars...
Usage: WhichClass or WhichClass package.name (note no .class)
Apologies for the lack of comments ...
import java.io.File;
import java.io.IOException;
import java.util.Enumeration;
import java.util.StringTokenizer;
import java.util.Vector;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;
public final class WhichClass {
private WhichClass() {
}
static Vector<String> scratchVector;
public static void main(final String[] argv) {
Vector v;
if ((argv.length == 0) || "-all".equals(argv[0])) {
v = findClass(null);
} else {
v = findClass(argv[0]);
}
for (int i = 0; i < v.size(); i++) {
System.out.println(v.elementAt(i));
}
}
static String className(final String classFile) {
return classFile.replace('/', '.').substring(0, classFile.length() - ".class".length());
}
static Vector findClass(final String className) {
if (className != null) {
scratchVector = new Vector<String>(5);
} else {
scratchVector = new Vector<String>(5000);
}
findClassInPath(className, setupBootClassPath());
findClassInPath(className, setupClassPath());
return scratchVector;
}
static void findClassInPath(final String className, final StringTokenizer path) {
while (path.hasMoreTokens()) {
String pathElement = path.nextToken();
File pathFile = new File(pathElement);
if (pathFile.isDirectory()) {
try {
if (className != null) {
String pathName = className.replace('.', System.getProperty("file.separator").charAt(0)) + ".class";
findClassInPathElement(pathName, pathElement, pathFile);
} else {
findClassInPathElement(className, pathElement, pathFile);
}
} catch (IOException e) {
e.printStackTrace();
}
} else if (pathFile.exists()) {
try {
if (className != null) {
String pathName = className.replace('.', '/') + ".class";
ZipFile zipFile = new ZipFile(pathFile);
ZipEntry zipEntry = zipFile.getEntry(pathName);
if (zipEntry != null) {
scratchVector.addElement(pathFile + "(" + zipEntry + ")");
}
} else {
ZipFile zipFile = new ZipFile(pathFile);
Enumeration entries = zipFile.entries();
while (entries.hasMoreElements()) {
String entry = entries.nextElement().toString();
if (entry.endsWith(".class")) {
String name = className(entry);
scratchVector.addElement(pathFile + "(" + entry + ")");
}
}
}
} catch (IOException e) {
System.err.println(e + " while working on " + pathFile);
}
}
}
}
static void findClassInPathElement(final String pathName, final String pathElement, final File pathFile)
throws IOException {
String[] list = pathFile.list();
for (int i = 0; i < list.length; i++) {
File file = new File(pathFile, list[i]);
if (file.isDirectory()) {
findClassInPathElement(pathName, pathElement, file);
} else if (file.exists() && (file.length() != 0) && list[i].endsWith(".class")) {
String classFile = file.toString().substring(pathElement.length() + 1);
String name = className(classFile);
if (pathName != null) {
if (classFile.equals(pathName)) {
scratchVector.addElement(file.toString());
}
} else {
scratchVector.addElement(file.toString());
}
}
}
}
static StringTokenizer setupBootClassPath() {
String classPath = System.getProperty("sun.boot.class.path");
String separator = System.getProperty("path.separator");
return new StringTokenizer(classPath, separator);
}
static StringTokenizer setupClassPath() {
String classPath = System.getProperty("java.class.path");
String separator = System.getProperty("path.separator");
return new StringTokenizer(classPath, separator);
}
}

If you know the fully qualified name of the class, say somelib.Owner, you can try calling the following in your code:
public void foo() {
URL url = somelib.Owner.class.getClassLoader().getResource("somelib/Owner.class");
System.out.println(url);
}

How to get all classes names in a package? [duplicate]

This question already has answers here:
Can you find all classes in a package using reflection?
(30 answers)
Closed 9 years ago.
So I have a package that has classes that extend JPanel and I want to add them as tabs dynamically. At the beginning I used a factory and I registered all the classes in it and it worked, but now I want load all the classes in the package without knowing their names. I've tried several things including Reflections library (which I found very confusing) and I couldn't get them to work. I appreciate any help.
Here's one of my trials:
public static void registerTab() {
String pkg = TabA.class.getPackage().getName();
String relPath = pkg.replace('.', '/');
URL resource = ClassLoader.getSystemClassLoader().getResource(relPath);
if (resource == null) {
throw new RuntimeException("Unexpected problem: No resource for "
+ relPath);
}
File f = new File(resource.getPath());
String[] files = f.list();
for (int i = 0; i < files.length; i++) {
String fileName = files[i];
String className = null;
String fileNm = null;
if (fileName.endsWith(".class")) {
fileNm = fileName.substring(0, fileName.length() - 6);
className = pkg + '.' + fileNm;
}
if (className != null) {
if (!tabClasses.containsKey(className))
tabClasses.put(fileNm, className);
}
}
}

Here is a custom solution I developed to find all the classes of a package:
public class ClassFinder {
private static final char PKG_SEPARATOR = '.';
private static final char DIR_SEPARATOR = '/';
private static final String CLASS_FILE_SUFFIX = ".class";
private static final String BAD_PACKAGE_ERROR = "Unable to get resources from path '%s'. Are you sure the package '%s' exists?";
public static List<Class<?>> find(String scannedPackage) {
String scannedPath = scannedPackage.replace(PKG_SEPARATOR, DIR_SEPARATOR);
URL scannedUrl = Thread.currentThread().getContextClassLoader().getResource(scannedPath);
if (scannedUrl == null) {
throw new IllegalArgumentException(String.format(BAD_PACKAGE_ERROR, scannedPath, scannedPackage));
}
File scannedDir = new File(scannedUrl.getFile());
List<Class<?>> classes = new ArrayList<Class<?>>();
for (File file : scannedDir.listFiles()) {
classes.addAll(find(file, scannedPackage));
}
return classes;
}
private static List<Class<?>> find(File file, String scannedPackage) {
List<Class<?>> classes = new ArrayList<Class<?>>();
String resource = scannedPackage + PKG_SEPARATOR + file.getName();
if (file.isDirectory()) {
for (File child : file.listFiles()) {
classes.addAll(find(child, resource));
}
} else if (resource.endsWith(CLASS_FILE_SUFFIX)) {
int endIndex = resource.length() - CLASS_FILE_SUFFIX.length();
String className = resource.substring(0, endIndex);
try {
classes.add(Class.forName(className));
} catch (ClassNotFoundException ignore) {
}
}
return classes;
}
}
Then, just use:
List<Class<?>> classes = ClassFinder.find("com.package");