長い文字列があり、各文字の出現回数を統計し、逆記述に従って出力する必要がある.

/**
 * ClassName: CountStr
 *
 * @author leegoo
 * @Description:
 * @date 2019 07 03 
 */
public class CountStr {

    private static String str = "" +
            "Hello i'am jack," +
            "very glad to be here," +
            "my favourite subject is English . " +
            "and i like sports very much .  ";

    public static void main(String[] args) {
        Map<Character, Integer> map = new HashMap<>();
        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);
            if (c != 32) { //    
                if (map.containsKey(c)) {
                    Integer countNumber = map.get(c);
                    map.put(c, ++countNumber);
                } else {
                    map.put(c, 0);
                }
            }
        }
        //map     https://www.cnblogs.com/yucfeng/p/8794608.html
        map.entrySet().stream().sorted(Map.Entry.<Character, Integer>comparingByValue().reversed()).forEach(
                e -> System.out.println("key:"+e.getKey()+",value="+e.getValue())
        );
    }
}

key:e,value=8
key:i,value=5
key:a,value=4
key:l,value=4
key:r,value=4
key:s,value=4
key:o,value=3
key:t,value=3
key:c,value=2
key:h,value=2
key:m,value=2
key:u,value=2
key:v,value=2
key:y,value=2
key:b,value=1
key:d,value=1
key:g,value=1
key:j,value=1
key:k,value=1
key:,,value=1
key:n,value=1
key:.,value=1
key:E,value=0
key:H,value=0
key:f,value=0
key:',value=0
key:p,value=0