统计一个字符串中每一个字符出现的次数
- 2020 年 1 月 23 日
- 筆記
本文提供三种方案，本质都是先将字符串转为数组：
- String.charAt(index)
- String.split("")
- String.toCharArray()
具体如下：
/** * 通过String.charAt(index)获取字符串中的字符 * @param str */ public static void count(String str){ Map<Character, Integer> map = new HashMap<Character, Integer>(); int total = 0; Character tmp = null; for (int i=0;i<str.length(); i++) { tmp = str.charAt(i); total = 1; if (map.containsKey(tmp)) { total = map.get(tmp)+1; } map.put(tmp, total); } PrintUtill.printlnRule(); PrintUtill.println(map); } /** * String.charAt(index)的变种，将最后存储的Character类型转为String类型 * @param str */ public static void count2(String str){ Map<String, Integer> map = new HashMap<String, Integer>(); int total = 0; String tmp = null; String maxChar = str.charAt(0) + ""; int maxToal = 1; for (int i=0;i<str.length(); i++) { tmp = str.charAt(i) + ""; total = 1; if (map.containsKey(tmp)) { total = map.get(tmp)+1; } map.put(tmp, total); if (maxToal<total) { maxToal = total; maxChar = tmp; } } PrintUtill.printlnRule(); PrintUtill.println(map); PrintUtill.println( "出现次数最多的字母是：" + maxChar + ",出现次数是：" + maxToal); } /** * 通过String.split("")将字符串直接切割成字符串数组 * @param str */ public static void count3(String str){ Map<String, Integer> map = new HashMap<String, Integer>(); int total = 0; String[] myStrs = str.split(""); String tmp = null; for (int i=0;i<myStrs.length; i++) { tmp = myStrs[i]; total = 1; if (map.containsKey(tmp)) { total = map.get(tmp)+1; } map.put(tmp, total); } PrintUtill.printlnRule(); PrintUtill.println(map); } /** * 通过String.toCharArray()将字符串转为char数组 * @param str */ public static void count4(String str){ Map<String, Integer> map = new HashMap<String, Integer>(); int total = 0; char[] myStrs = str.toCharArray(); String tmp = null; for (int i=0;i<myStrs.length; i++) { tmp = myStrs[i] + ""; total = 1; if (map.containsKey(tmp)) { total = map.get(tmp)+1; } map.put(tmp, total); } PrintUtill.printlnRule(); PrintUtill.println(map); }
