java - ArrayList 数据无法正确传输到 Java 中的数组

Question

当我注销sectionList时，有20个项目；由于某种原因，除了最后一项之外的所有项都被输入到数组部分中。有人能看出这里出了什么问题吗？

更新:我发布了整个类(class)的问题；它相对较短。它来自 Android 应用程序。

public class ItemAdapter extends ArrayAdapter<ItemObject> implements
        SectionIndexer {

    private HashMap<String, Integer> alphaIndexer;
    private String[] sections;
    private LayoutInflater inflater;

    public ItemAdapter(Context context, ItemObject[] objects) {
        super(context, R.layout.item_row_layout, objects);

        inflater = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        alphaIndexer = new HashMap<String, Integer>();
        int size = objects.length;

        for (int i = 0; i < size; i++) {

            ItemObject it = objects[i];
            String name = it.name;
            String s = name.substring(0, 1);
            s = s.toUpperCase();

            if (!alphaIndexer.containsKey(s)) {
                alphaIndexer.put(s, i);
            }
        }

        Set<String> sectionLetters = alphaIndexer.keySet();
        ArrayList<String> sectionList = new ArrayList<String>(sectionLetters);
        Collections.sort(sectionList);
        sections = new String[sectionList.size()];

        sections = sectionList.toArray(new String[sectionList.size()]);


    }

Answer 1

    for (int i = 0; i < sectionList.size(); i++) {
        sections[i] = sectionList.get(i);
    }

    for (int i = 0; i < sections.length - 1; i++) {
        sections[i] = sectionList.get(i);
    }

为什么要在这里复制数组两次？另外，为什么不使用迭代器呢？实际上，您真正应该使用的是 ArrayList.toArray转换为 String[]，例如

sections = sectionList.toArray(new String[sectionList.size()]);

此外，您可以使用 TreeMap 而不是 HashMap 对键进行排序，只需执行 TreeMap.keySet ...

The set's iterator returns the keys in ascending order.