This method accesses the value of a Map entry, using a key that was retrieved from a keySet iterator. It is more efficient to use an iterator on the entrySet of the map, to avoid the Map.get(key) look

sonar扫描的严重问题对应。

代码写这样就会报上面的严重问题

Map<String, Integer> params = new HashMap<String, Integer>();
        params.put("resultID", 1);
        params.put("execID", 2);
        params.put("num", 3);

        Map<String, Object> mapOut = new HashMap<String, Object>();
        // Map<String, Integer> 转 HashMap<String, Object>
        Set<String> set = params.keySet();
        for (String key : set) {
            Integer value = params.get(key);
            mapOut.put(key,value);
        }

意思是说要避免用.get(key)，可能有点脱裤子放屁的感觉。

修改后

        for (Map.Entry<String, Integer> entry : params.entrySet()) {
            mapOut.put(entry.getKey(),entry.getValue());
        }

参考这篇

https://www.cnblogs.com/dreammyone/articles/9960400.html

还有这篇

https://blog.csdn.net/jdsjlzx/article/details/34487299

This method accesses the value of a Map entry, using a key that was retrieved from a keySet iterator. It is more efficient to use an iterator on the entrySet of the map, to avoid the Map.get(key) lookup.
解释：
很多人都这样遍历Map，没错，但是效率很低，先一个一个的把key遍历，然后在根据key去查找value，这不是多此一举么，为什么不遍历entry（桶）然后直接从entry得到value呢？它们的执行效率大概为1.5:1（有人实际测试过）。
我们看看HashMap.get方法的源代码： 1. public V get(Object key) { 2. if (key == null) 3. return getForNullKey(); 4. int hash = hash(key.hashCode()); 5. for (Entry<K,V> e = table[indexFor(hash, table.length)]; 6. e != null; 7. e = e.next) { 8. Object k; 9. if (e.hash == hash && ((k = e.key) == key || key.equals(k))) 10. return e.value; 11. } 12. return null; 13. }
从这里可以看出查找value的原理，先计算出hashcode，然后散列表里取出entry，不管是计算hashcode，还是执行循环for以及执行equals方法，都是CPU密集运算，非常耗费CPU资源，如果对一个比较大的map进行遍历，会出现CPU迅速飚高的现象，直接影响机器的响应速度，在并发的情况下，简直就是一场灾难。
解决方法： 1. for (Map.Entry<String, JMenu> entry : menuList.entrySet()) { 2. mb.add(entry.getValue());
}
for(Map.Entry<String, List<BlackListDO>> tempEntiy: companyBlackItemsMap.entrySet()) {
String key = tempEntiy.getKey();
List<BlackListDO> eachCompanyBlackItems = tempEntiy.getValue();

This method accesses the value of a Map entry, using a key that was retrieved from a keySet iterator. It is more efficient to use an iterator on the entrySet of the map, to avoid the Map.get(key) look

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