Class2.java

import org.checkerframework.checker.nullness.qual.NonNull;
import org.checkerframework.checker.nullness.qual.Nullable;

public class Class2 {
    public static @Nullable Object field;
    public @Nullable Object instanceField;

    public static void method(Class1 class1) {
        Class1.method();
        @NonNull Object o = Class1.field;
        Class1.method2();
        @NonNull Object o2 = field;

        class1.instanceMethod();
        @NonNull Object o3 = class1.instanceField;
    }

    void test() {
        Class1.method3(this);
        @NonNull Object o = instanceField;
    }
}