Java中垃圾收集器的工作

public class GCTest {
    static class A {
        private String myName;
        public A(String myName) {
            this.myName = myName;
        }
    }

    public static void main(String[] args) {
        A a1 = new A("a1");
        A a2 = new A("a2");
        ArrayList list = new ArrayList();
        list.add(a1);
        A[] mas = new A[2];
        mas[0] = a2;
        a2 = a1;
        clear(mas);
        a1 = null;
        a2 = null;
        System.gc();
        // some code
        ...
    }

    private static void clear(A[] mas) {
        mas = null;
    }
}

如果object == null它变成了垃圾？

我认为a1,a2和mas在调用System.gc()时可用于垃圾收集,因为它处于null状态.或者我错了？