how do I get all the classes in the javaapplication7 package?

There is a package javaapplication7, it has 3 simple classes A, B,C, I find it difficult to get them.

3 answers

Here is an example of a class that scans a package and returns a list of its classes

вpublic 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?";

/**
 * Возвращает список классов в пакете
 */
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<>();
    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<>();
    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;
}

}

Example of calling

List<Class<?>> classes = ClassFinder.find("examples.concurrency");
 4
Author: Константин Полищук, 2019-05-22 07:57:44

You can use the library: Class graph Maven Central

Example: 

try (ScanResult scanResult = new ClassGraph()
        .whitelistPackages("javax.persistence")      // Сканирует пакет javax.persistence и все его подпакеты
        .scan()) {
    for (ClassInfo classInfo : scanResult.getAllClasses()) {
        System.out.println(classInfo.getName());
    }
}
 1
Author: aleshka-batman, 2019-05-22 07:55:16

I can offer a library Reflections. You can use it to easily get information about classes for a given package:

private static List<Class<?>> getAllClassesFrom(String packageName) {
    return new Reflections(packageName, new SubTypesScanner(false))
            .getAllTypes()
            .stream()
            .map(name -> {
                try {
                    return Class.forName(name);
                } catch (ClassNotFoundException e) {
                    return null;
                }
            })
            .filter(Objects::nonNull)
            .collect(Collectors.toList());
}

Dependency:

<dependency>
        <groupId>org.reflections</groupId>
        <artifactId>reflections</artifactId>
        <version>0.9.10</version>
</dependency>
 1
Author: Artem Konovalov, 2019-05-22 09:03:33