TreeMap排序位置访问

Question

如果我想检查TreeMap中第一个索引位置的值是否为xyz，那么请执行xyz 否则，如果第一个索引位置的值是abc，则执行abc。我怎么能写这个？因为我想在TreeMap中访问排列的索引。我想按顺序逐个访问TreeMap的排序键。需要帮助

Answer 1

最快和最丑的黑客可能只是

List<KeyType> keyList = new ArrayList<>(myTreeMap.keySet());
KeyType nthKey = keyList.get(nthIndex);

但是当我想按索引查找条目时，我会问自己为什么我首先使用TreeMap？使用List并调用sort？

会更有效率吗？

Answer 2

//this code iterates through all the keys in sorted order
treeMap.keySet().forEach(key -> {
    //use key to do whatever you need
});

修改

//this code iterates through all entries (from first, second, third, ... to last)
tree.entrySet().forEach(entry -> {
    key = entry.getKey();
    value = entry.getValue();
    //use key and value to do whatever you need
});

EDIT2

//this codes finds the first key whose value equals the desired value
Object key = tree.entrySet().stream()
                            .filter(e -> e.getValue().equals(desiredValue))
                            .map(Entry::getKey)
                            .findFirst()
                            .get();