集合之TreeMap

TreeMap

底层数据结构是二叉树
如何保证键的唯一: 利用存的特点
如何保证键的可排序: 利用取的特点 左跟右
在map中数据结构只对键有效
TreeMap 有Map的键值对的特性：还可以进行排序，默认自然排序

利用正则和TreeMap 实现一段英文的单词记录

　　

 String str = "Failure is probably the, fortification in your pole. " +
                 "It is like a peek your wallet as. the thief, when you are" +
                 " thinking how to spend several? hard-won lepta, when you " +
                 "are wondering whether ?new money, it has laid background." +
                 " Because of you, then at the heart of the most lax, alert," +
                 " and most " +
                 "low awareness, and left it godsend failed.";

 String s = "\\d+.\\d+|\\w+";//正则表达式
 Pattern  pattern=Pattern.compile(s);
 Matcher  ma=pattern.matcher(str);  

 TreeMap<String, Integer> tree = new TreeMap<String,Integer>();

 while(ma.find()){

     String c = ma.group();//获取用正则取出来的单词

     if(!tree.containsKey(c)){//去重和计数
         tree.put(c, 1);
     }else{
         int num = tree.get(c)+1;
         tree.put(c, num);
     }
 }

 //遍历：
 Set<String> set = tree.keySet();
 for (String key : set) {
     System.out.println(key+"("+tree.get(key)+")");
 }

 //TreeMap排序：
 TreeMap<Person,String> map =new TreeMap<Person,String>(new java.util.Comparator<Person>(){//实现Comparator接口

     @Override
     public int compare(Person o1, Person o2) {//按实际要求重写该方法，必要时使用三门运算符
         return -(o1.getHandsome()-o2.getHandsome());
     }

 } );