如何在Java中从ArrayList中删除dulpicates？

Question

Set<Object> valueSet = new HashSet<Object>();
        for(HashMap<String, Object> map: mDataList){
                valueSet.addAll(map.values());
        }

但是我们不能在集合中存储HashMap。我想要HashMap与键，值对作为返回值，这将被添加到列表中。也就是说，最终的值应该采用ArrayList>格式。

你能在这方面帮助我吗？谢了。

Answer 1

Set应该能够包含一个HashMap。

我假设这里的重复表示键，值对在2个HashMap之间是相同的。在这种情况下，您可以尝试

Set<HashMap<String, Object>> abc = new HashSet<HashMap<String, Object>>();
HashMap<String, Object> a1 = new HashMap<String, Object>();
a1.put("a", "a");

HashMap<String, Object> a2 = new HashMap<String, Object>();
a2.put("a", "a");

HashMap<String, Object> a3 = new HashMap<String, Object>();
a3.put("c", "c");

abc.add(a1);
abc.add(a2);
abc.add(a3);

for (HashMap<String, Object> each : abc){
    System.out.println(each.toString()); //{a=a}, {c=c}
}

根据您的评论编辑

String yourkey = "key";
List<HashMap<String, Object>> oldList = new ArrayList<HashMap<String, Object>>();

HashMap<String, Object> a1 = new HashMap<String, Object>();
a1.put(yourkey, "1");

HashMap<String, Object> a2 = new HashMap<String, Object>();
a2.put(yourkey, "1");

HashMap<String, Object> a3 = new HashMap<String, Object>();
a3.put(yourkey, "2");

oldList.add(a1);
oldList.add(a2);
oldList.add(a3);

HashMap<Object, Object> newMap = new HashMap<Object, Object>();
for (HashMap<String, Object> each : oldList){
    // Put the value as key. Duplicate will be overridden
    newMap.put( each.get(yourkey), each);
}

List<HashMap<String, Object>> noDuplicateList = new ArrayList<HashMap<String, Object>>();
for (Object each : newMap.keySet()) {
    noDuplicateList.add( (HashMap)newMap.get(each) );
}

System.out.println(noDuplicateList); // [{key=2}, {key=1}]