java - 对两个用户定义类型Library类的Arraylist进行排序和合并

Question

目标:我必须有两个 OSD 类型的排序数组列表(导入库的类部分)。我需要将它们合并以以最优化的方式创建最终的排序列表(按时间降序排列)。

Problem : I can't modify the user defined OSD class as its part of an library and hence I cant edit and make it implements Comparable class. I have already created the function which performs the task, but it I want to optimize the code and make it less expensive.

我遇到过许多涉及实现 Comparable 的解决方案，但我做不到。

我想要优化以获得更好性能的当前工作代码

private ArrayList<OSD> latestFistSortMergeOsds(
            ArrayList<OSD> awbThingTypeOSDs,
            ArrayList<OSD> LDDthingTypeOSDs) {
        ArrayList<OSD> sortedOsds = new ArrayList<OSD>();
        ArrayList<Long> timestampList = null;

        HashMap<Long, OSD> awbThingTypeOSDsHmap = null;
        if (awbThingTypeOSDs != null) {
            awbThingTypeOSDsHmap = new HashMap<Long, OSD>();
            for (OSD mOSD : awbThingTypeOSDs) {

                awbThingTypeOSDsHmap.put(mOSD.getUpdatedOn()
                        .getTime(), mOSD);
            }
            Log.i("sorted", "hmap" + awbThingTypeOSDsHmap);
        }
        HashMap<Long, OSD> LDDthingTypeOSDsHmap = null;
        if (LDDthingTypeOSDs != null) {
            LDDthingTypeOSDsHmap = new HashMap<Long,OSD>();
            for (OSD nOSD : LDDthingTypeOSDs) {

                LDDthingTypeOSDsHmap.put(nOSD.getUpdatedOn()
                        .getTime(), nOSD);
            }
        }
        // merge n sort timestamp
        if (awbThingTypeOSDsHmap != null) {
            timestampList = new ArrayList<Long>(awbThingTypeOSDsHmap.keySet());

            if (LDDthingTypeOSDsHmap != null) {
                ArrayList<Long> timestampListLDD = new ArrayList<Long>(
                        LDDthingTypeOSDsHmap.keySet());
                timestampList.addAll(timestampListLDD);
            }
            Collections.sort(timestampList, Collections.reverseOrder());// descending
            Log.i("sorted", "sorted keyList" + timestampList);
        }

        // merge sorted osds- latest first
        // timestamplist is sorted in desc order
        if (timestampList != null) {
            for (Long timestampKey : timestampList) {
                RareMediaCompanyOSD osd = null;

                osd = awbThingTypeOSDsHmap.get(timestampKey);
                if (osd == null) {
                    osd = LDDthingTypeOSDsHmap.get(timestampKey);
                }

                sortedOsds.add(osd);

            }
        }

        return sortedOsds;
    }

我引用了以下链接 Comparing Long values using Collections.sort(object)

Comparing Long values using Collections.sort(object)

How to sort ArrayList<Long> in Java in decreasing order?

请建议更好地使用 Hashmap，或者我应该使用其他 DS 而不是 hashmap 来优化代码。

P.S:它不是这些问题的重复，因为我无法编辑类并实现类似的，因为它是库的一部分。

谢谢!

Answer 1

我建议创建一个holder类，它保存一个OSD对象，该对象又实现Comparable

public class OSDHolder implements Comparable<OSDHolder> {

    private final OSD obj;

    public OSDHolder(OSD obj) {
        this.obj = obj;
    }

    public long getTiming() {
        this.obj.getUpdatedOn().getTime();
    }

    @Override
    public int compareTo(OSDHolder o) {
        if (this.getTiming() > o.getTiming())
            return 1;
        else if (this.getTiming < o.getTiming())
            return -1;
        return 0;
    }
} 

然后，您可以简单地将两个列表的内容添加到一个列表中，作为 OSDHolder 类型

ArrayList<OSDHolder> holders = new ArrayList<>();

for (OSD osd:awbThingTypeOSDs) {
    holders.add(new OSDHolder(osd));
}

for (OSD osd:LDDthingTypeOSDs) {
    holders.add(new OSDHolder(osd));
}

然后使用 Collections.sort() 或 Arrays.sort() 对 holders 进行排序