Java ArrayList获取值

帮助从ArrayList获取值

data = new ArrayList<Map<String, String>>();
for (int i = 0; i < marks.length; i++) {
    HashMap<String, String> m = new HashMap<String, String>();
    m.put("title", marks[i].getUserName());
    m.put("mark", marks[i].getMark().toString());
    m.put("type", marks[i].getType().toString());
    m.put("description", marks[i].getDescription());
    data.add(m);
}

试图从适配器中取出ArrayList并写入值​​对数组执行以下操作：

data = simpleAdapter.getData();
MarksRead[] marksReads = new MarksRead[data.size()];
for (int i = 0; i < data.size(); i++) {
    marksReads[i].setDescription(data(i).get("description"));
    marksReads[i].setMark(Integer.valueOf(data.get(i).get("mark")));
    marksReads[i].setType(Integer.valueOf(data.get(i).get("type")));
}

在线标记READS[i].setDescriptiondatai.getdescription；输出为异常NullPointerException

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帮助，如何正确操作。

您必须先创建对象，然后才能使用它

for (int i = 0; i < data.size(); i++) {
    marksReads[i] = new MarksReads();
    marksReads[i].setDescription(data(i).get("description"));
    marksReads[i].setMark(Integer.valueOf(data.get(i).get("mark")));
    marksReads[i].setType(Integer.valueOf(data.get(i).get("type")));
 }