//方式1
  public static void letterCount1(String s) {
   s=s.replaceAll(" +", "");
    //1,转换成字符数组
   char c[]=s.toCharArray();
   
   Map<Character, Integer> tree=new TreeMap<Character, Integer>();
   for (int i = 0; i < c.length; i++) {
  //第一次：a,1
  //第二次：a,2 
    //2,获取键所对应的值
  Integer value=tree.get(c[i]);
//     反编译：Integer value = (Integer)tree.get(Character.valueOf(c[i]));
    //3,存储判断
  tree.put(c[i], value==null? 1:value+1);
   }
   
   //如果要求结果格式：a(5)b(4)c(3)d(2)e(1)
   StringBuilder sbu=new StringBuilder();
   for(Character key:tree.keySet()){
  Integer count=tree.get(key);
  sbu.append(key).append("(").append(count).append(")");
   }
   //将sbu转换为字符串
   System.out.println(sbu.toString());
 }
   
  //方式2 使用流
  //这个在测试特殊字符,比如\  \n时,他的顺序会不对,这个是Map造成的
  //解决办法使用TreeMap
  public static void letterCount2(String s) {
   s=s.replaceAll(" +", "");
   TreeMap<String, Long> result = Arrays.stream(s.split(""))
                   .sorted()
//                     .collect(Collectors.groupingBy(Function.identity(),Collectors.counting()));
                     .collect(Collectors.groupingBy(Function.identity(),TreeMap::new,Collectors.counting()));
    System.out.println(result);
   
  }
  
  //方式3 使用Collections.frequency
  //其实就是字符串变成集合存每个字串,把每个字串循环跟集合比较
  public static void letterCount3(String s) {
   s=s.replaceAll(" +", "");
   List<String> list=Arrays.asList(s.split(""));
   Map<String,Integer> map=new TreeMap<String, Integer>();
   for (String str : list) {
    map.put(str, Collections.frequency(list, str));
  }
   System.out.println(map);
  }
  
  //方式4
  public static void letterCount4(String s) {
   s=s.replaceAll(" +", "");
   String[] strs = s.split("");
   Map<String,Integer> map=new TreeMap<String, Integer>();
   for (String str : strs) {
    map.put(str, stringCount(s, str));
  }
   System.out.println(map);
  }
  
  
  //方式5
  public static void letterCount5(String s) {
   s=s.replaceAll(" +", "");
   String[] strs = s.split("");
   Map<String,Integer> map=new TreeMap<String, Integer>();
   for (String str : strs) {
    map.put(str, stringCount2(s, str));
  }
   System.out.println(map);
  }
  
  
  
  //巧用split
  public static int stringCount(String maxstr, String substr) {
  // 注意
  // 1.比如qqqq,没有找到,则直接返回这个字符串
  // 2.比如qqqjava,末尾没有其他字符,这时也不会分割,所以可以添加一个空格
  // 3.java11开头没有字符，没有关系，自动空填充
  // 4.对于特殊字符,要注意使用转义符
  int count = (maxstr + " ").split(substr).length - 1;
  // System.out.println("\"" + minstr + "\"" + "字符串出现次数：" + count);
  return count;
 }

  //如果要不区分大小写，则compile(minstr,CASE_INSENSITIVE)
 public static int stringCount2(String maxstr, String substr) {
  int count = 0;
  Matcher m = Pattern.compile(substr).matcher(maxstr);
  while (m.find()) {
   count++;
  }
    return count;
 }
  

 public static void wordStringCount(String s) {
   //这里开始是字符串,分割后变成字符串流
    Map<String, Long> result = Arrays.stream(s.split("\\s+"))
                   .map(word -> word.replaceAll("[^a-zA-Z]", ""))
                        .collect(Collectors.groupingBy(Function.identity(),Collectors.counting()));
    System.out.println(result);
   
  }

 //统计一个文本中单词的个数
  public static void wordFileCount(String path) throws IOException{
   //这里一开始字符串流
   //先分割
   //在变成字符流
   //在筛选
    Map<String, Long> result = Files.lines(Paths.get(path),Charset.defaultCharset())
              .parallel()
      //字符串流--分割--字符串流
      .flatMap(str->Arrays.stream(str.split(" +"))) 
      .map(word -> word.replaceAll("[^a-zA-Z]", ""))
     //去掉空
      .filter(word->word.length()>0) 
     .collect(Collectors.groupingBy(Function.identity(),Collectors.counting()));
   System.out.println(result);
  }

public void testName() {
      System.out.println("a");
   }

    public void testName(String ... s) {
        //不传参数,s会默认初始化一个对象
     System.out.println("b");
  }