Java通过外部类对象引用内部类属性

Question

I'm having the problem my title describes. I have an outer class called GAINEntities with an inner class in it called Entities. My goal is to reference the attributes of the inner class through objects of the outer class. I have a function readGainEntities(String inputUrl) which returns a Vector. Thus, in my method i call readGainEntities method and set its content to a new Vector

Example Code:

protected static Vector<LinkedHashTreeMap> getGainEntities(String inputUrl) {

    URL url = null;
    try {
        url = new URL(inputUrl);

    } catch (MalformedURLException e2) {
        // TODO Auto-generated catch block
        e2.printStackTrace();
    }
    URLConnection yc = null;
    try {
        yc = url.openConnection();
    } catch (IOException e2) {
        // TODO Auto-generated catch block
        e2.printStackTrace();
    }
    String userpass = "" + ":" + "";
    String basicAuth = "Basic "
            + new String(new Base64().encode(userpass.getBytes()));
    yc.setRequestProperty("Authorization", basicAuth);
    BufferedReader in = null;
    try {
        in = new BufferedReader(new InputStreamReader(yc.getInputStream()));
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    Gson gson = new Gson();
    List<LinkedHashTreeMap> items = null;
    try {
        items = gson.fromJson(in.readLine(),
                new TypeToken<List<LinkedHashTreeMap>>() {
                }.getType());
    } catch (IOException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }

    Vector<LinkedHashTreeMap> sessions = new Vector<LinkedHashTreeMap>();
    for (int i = 0; i < items.size(); i++) {
        sessions.add(items.get(i));
    }

    return sessions;
}



public static Vector<GAINEntities> readGainentities(String inputUrl) {
    Vector<GAINEntities> exp = new Vector<GAINEntities>();
    Vector<LinkedHashTreeMap> sessions = getGainEntities(inputUrl);
    Iterator it = sessions.iterator();
    while (it.hasNext()) {
        LinkedHashTreeMap next = (LinkedHashTreeMap) it.next();
        GAINEntities input = new GAINEntities();
        input.setObjectID((String) next.get("objectId"));
        input.setSubobjectID((String) next.get("subobjectId"));

        LinkedHashTreeMap<String, String> lhmt = (LinkedHashTreeMap<String, String>) next
                .get("attributes");

        data.GAINEntities.Attributes atts = input.new Attributes();
        atts.setAttributeStart(Double.parseDouble(String.valueOf(lhmt
                .get("start"))));
        atts.setAttributeEnd(Double.parseDouble(String.valueOf(lhmt
                .get("end"))));

        input.setAttributes(atts);
        input.setAccountID((String) next.get("accountId"));
        input.setID((String) next.get("_id"));
        input.setV(Double.parseDouble(String.valueOf(next.get("__v"))));
        ArrayList<LinkedHashTreeMap<String, String>> al = (ArrayList<LinkedHashTreeMap<String, String>>) next
                .get("entities");
        ArrayList<Entities> ents = new ArrayList<Entities>();

        for (int i = 0; i < al.size(); i++) {
            ents.add(input.new Entities(al.get(i).get("ntype"), al.get(i)
                    .get("source"), al.get(i).get("lod"), al.get(i).get(
                    "type"), al.get(i).get("label"), Double
                    .parseDouble(String
                            .valueOf(al.get(i).get("confidence"))),
                    Double.parseDouble(String.valueOf(al.get(i).get(
                            "relevance")))));
        }
        input.setEntities(ents);

        exp.add(input);
        // System.out.println(input);
        // System.out.println(input);
    }

    return exp;
}

Then in my Translate method:

public static String translateGAINEntities(String url) {
    LogicFactory.initialize();
    Vector<GAINEntities> exp = readGainEntities.readGainentities(url);
for (int i = 0; i < exp.size(); i++) {
        LogicFactory.initialize();
        GAINEntities gexp = exp.get(i);
System.out.println("HEREEE  \t" + gexp.getEntities()); <-- returns empty.

So,is there something wrong with my code as im still unsure how to reference the Entities attributes through the GAINEntities objects which readGainEntities returns

Answer 1

Generally you can reference the attributes of the Inner class outside the Outer class only when you have an Object of the Outer class:

new Outer().new Inner().doStuff();

provided that the doStuff() method is public.

If the Inner class is static then you can reference it as:

new Outer.Inner().doStuff();

In your example you do not show the classes involved.