TestWeak.java

import jdk.crac.*;

import java.util.HashSet;
import java.util.Set;

public class TestWeak {
    public static void main(String[] args) throws Exception {
        Context<Resource> context = new StrongContextWrapper(Core.getGlobalContext());

        context.register(new Resource() {
            @Override
            public void beforeCheckpoint(Context<? extends Resource> context) throws Exception {
                System.out.println("beforeCheckpoint() invoked");
            }

            @Override
            public void afterRestore(Context<? extends Resource> context) throws Exception {
                System.out.println("afterCheckpoint() invoked");

            }
        });

        //try force gc
        for (int i = 0; i < 10; i++) {
            System.gc();
        }

        Core.checkpointRestore();
    }
}

class StrongContextWrapper extends Context<Resource> {
    private Context<Resource> context;
    private Set<Resource> strongLinks;

    public StrongContextWrapper(Context<Resource> context) {
        this.context = context;
        this.strongLinks = new HashSet<>();
    }

    @Override
    public void beforeCheckpoint(Context<? extends Resource> context) throws CheckpointException {
        throw new CheckpointException("should not call this");
    }

    @Override
    public void afterRestore(Context<? extends Resource> context) throws RestoreException {
        throw new RestoreException("should not call this");
    }

    @Override
    public void register(Resource resource) {
        strongLinks.add(resource);
        context.register(resource);
    }

    public void deregister(Resource resource) {
        strongLinks.remove(resource);
    }
}