java中TreeMap统计字符个数

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package study;import java.util.Arrays;import java.util.HashSet;import java.util.Map;import java.util.Scanner;import java.util.TreeMap;import java.util.TreeSet;/*输入字符串统计里面单词的个数，以及里面字母出现的次数*/public class StringDemo {public static void main(String[] args) {System.out.println("请输入一个字符串：");Scanner reader = new Scanner(System.in);String in = reader.nextLine();//StringBuilder sb = wordCount(in);System.out.println(wordCount(in));System.out.println(chartCount(in));}public static TreeSet wordCount(String str) {//单词个数统计//StringBuilder sb = new StringBuilder();//sb.append("[");//String[] word = str.split(" ");//for(int i = 0;i < word.length - 1;i++) {//sb.append(word[i] + ",");//}//sb.append(word[word.length - 1]);//sb.append("] 共" + word.length + "个单词");//System.out.println(count);//return sb;/*上面的收集方式不能排除相同单词的出现，考虑使用set集合来过滤*/String[] token = str.split(" ");return new TreeSet(Arrays.asList(token));}/* * 考虑用键值对来存储每个字符的个数 * */public static TreeMap chartCount(String str) {//字符个数统计char[] charArray = str.toCharArray();TreeMap<Character,Integer> tp = new TreeMap<Character,Integer>();for(int i = 0;i < charArray.length;i++) {if(!tp.containsKey(charArray[i])) {tp.put(charArray[i], 1);}else {int count = tp.get(charArray[i]) + 1;tp.put(charArray[i], count);//根据TreeMap源码意思，当出现相同键，但其值不同，会用新添加的值进行替代}}return tp;}}
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