java如何在hashmap中首先迭代最大键字符串值

Question

我想先迭代最大键值。我的密码在这里。我有一些有价值的hashmap。我想先迭代最大键值，以便按照我的代码，它将首先替换最大键值

 HashMap<String, String> mapp=new HashMap<String, String>();
          mapp.put("ab","blue");
          mapp.put("abc","black");
          mapp.put("abcdef","green");
          mapp.put("abcd","pink");

for (Iterator it = alltyp.iterator(); it.hasNext();) {
  String finalstring = (String) it.next();
   Iterator it1=mapp.entrySet().iterator();
   while(it1.hasNext())
        {
         Map.Entry pairs = (Map.Entry) it1.next();
         String key_ = (String) pairs.getKey();
         String value_ = (String) pairs.getValue();
         finalstring = finalstring.replaceAll(key_, value_);
         }
     }

首先，它将迭代键值“abcdef”，然后是“abcd”，然后是“abc”，最后是“ab”。现在在while循环中，它将首先取代“abcdef”。 请给我你的建议

Answer 1

使用TreeMap对象而不是HashMap

在TreeMap上迭代将按升序给出键。只需在迭代时将这些值放入堆栈中，然后逐个弹出它们，然后瞧，现在您的键按降序排列

TreeMap<String, String> mapp = new TreeMap<String, String>();
mapp.put("ab","blue");
mapp.put("abc","black");
mapp.put("abcdef","green");
mapp.put("abcd","pink");

Stack<Entry<String, String>> stk = new Stack<Entry<String, String>>();
for (Entry<String, String> entry : mapp.entrySet()) {
    stk.push(entry);
}

while (!stk.isEmpty()) {
    Entry<String, String> entry = stk.pop();
    // Do something with entry
}

Answer 2

可以直接通过TreeMap完成；您只需要传递自己的比较器，它按长度降序排列键

    Map<String,String> mapp = new TreeMap<String,String>(new Comparator<String>(){
        @Override
        public int compare(String paramT1, String paramT2) {
            Integer t1 = paramT1.length();
            Integer t2 = paramT2.length();
            return t2.compareTo(t1);
        }

    });
     mapp.put("ab","blue");
     mapp.put("abc","black");
     mapp.put("abcdef","green");
     mapp.put("abcd","pink");

     for(String t : mapp.keySet()){
         System.out.println(" key :"+ t);
     }

我在博客上详细讨论了比较器here