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());
    }
    
} );