StaticInternMethod.java

import java.util.HashMap;
import java.util.Map;
import org.checkerframework.checker.interning.qual.*;

public class StaticInternMethod {

    private static Map<Integer, @Interned Foo> pool = new HashMap<Integer, @Interned Foo>();

    @SuppressWarnings("interning")
    public static @Interned Foo intern(Integer i) {
        if (pool.containsKey(i)) {
            return pool.get(i);
        }

        @Interned Foo f = new @Interned Foo(i);
        pool.put(i, f);
        return f;
    }

    static class Foo {
        public Foo(Integer i) {}
    }

    void test() {
        Integer i = 0;
        Foo f = new Foo(i);
        @Interned Foo g = intern(i);
    }
}