1 public class ADemo { 2 public static void main(String[] args) { 3 Scanner sc = new Scanner(System.in); 4 System.out.println("请输入字符串"); 5 String str = sc.next(); 6 toMap(str); 7 8 9 } 10 public static void toMap(String str){ 11 Map<Character,Integer> m = new HashMap<>(); 12 char ch; 13 for (int i = 0; i < str.length(); i++) { 14 ch = str.charAt(i); 15 if(m.keySet().contains(ch)){ 16 m.put(ch,m.get(ch)+1); //可以覆盖原来的值。 17 }else{ 18 m.put(ch,1); 19 } 20 } 21 for (Character key : m.keySet()) { 22 System.out.println(key+"出现的次数:"+m.get(key)); 23 } 24 }