忽略字母大小写情况下统计字符出现的次数

package lsh.element.algrithom;import java.util.Scanner;public class CountLetterIgnoreCase {public static void main(String[] args) {Scanner input = new Scanner(System.in);System.out.println("请输入带有字母的字符串： ");String str = input.nextLine();int[] countLetters = countLetters(str.toLowerCase());for (int i = 0; i < countLetters.length; i++) {System.out.println((char)('a'+i)+" 出现了 "+countLetters[i]+" 次;");}input.close();}/*** 巧妙地利用了被处理对象内部的结构关系* @param str* @return*/public static int[] countLetters(String str) {int[] counts = new int[26];for (char e : str.toCharArray()) {if(Character.isLetter(e)) {counts[e - 'a']++;}}return counts;}}