Java security manager removal — check your code free

Finds Java code that JDK 21/25 removed or refuses to run — Security Manager, sun.misc.Unsafe, javax.* imports, Applet, Thread.stop — before you leave Java 17. Runs entirely in your browser — nothing is uploaded.

package com.acme.billing;

import java.applet.Applet;
import java.net.URL;
import java.util.Locale;
import java.security.AccessController;
import java.security.PrivilegedAction;
import javax.security.auth.Subject;
import javax.persistence.Entity;
import javax.servlet.http.HttpServletRequest;
import javax.xml.bind.JAXBContext;
import sun.misc.Unsafe;
import com.sun.crypto.provider.SunJCE;

@Entity
public class InvoiceExporter {

private final Locale locale = new Locale("de", "DE");
    private final Integer retries = new Integer(3);
    private Thread workerThread;

public void bootstrap(String policyPath) throws Exception {
        System.setProperty("java.security.policy", policyPath);
        System.setSecurityManager(new SecurityManager());
        java.security.Policy.getPolicy().refresh();
        System.loadLibrary("acme_pdf");
    }

public String render(HttpServletRequest request) throws Exception {
        String endpoint = request.getParameter("endpoint");
        URL target = new URL(endpoint);
        JAXBContext ctx = JAXBContext.newInstance(Invoice.class);
        Object handler = Class.forName("com.acme.billing.PdfHandler").newInstance();
        handler.getClass().getDeclaredField("timeout").setAccessible(true);
        return AccessController.doPrivileged((PrivilegedAction<String>) () -> target.toString());
    }

public String runAs(Subject subject) throws Exception {
        return Subject.doAs(subject, (PrivilegedAction<String>) () -> "ok");
    }

public void shutdown() {
        workerThread.stop();
        System.runFinalization();
    }

private long address() {
        Unsafe unsafe = Unsafe.getUnsafe();
        return unsafe.allocateMemory(64L);
    }

private static native void writeHeader(long address);

@Override
    protected void finalize() throws Throwable {
        closeTempFiles();
        super.finalize();
    }

private void closeTempFiles() { }

static class LegacyPreview extends Applet { }
}

as of

Free here: Scans every .java file you open or the whole workspace and names each JDK 21/25 blocker on its line with the JEP that removed it and the replacement call.. In the editor: Exports the whole repository as one dated migration report — every file, blocker, JEP and replacement in Markdown and CSV — to hand to the team or attach to the upgrade ticket, and covers commercial and team-seat use. — that part asks for a licence key.

Same engine as the VS Code extension, byte for byte.