統計一個字元串中每一個字元出現的次數
- 2020 年 1 月 23 日
- 筆記
本文提供三種方案，本質都是先將字元串轉為數組：
- String.charAt(index)
- String.split("")
- String.toCharArray()
具體如下：
/** * 通過String.charAt(index)獲取字元串中的字元 * @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)的變種，將最後存儲的Character類型轉為String類型 * @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( "出現次數最多的字母是：" + maxChar + ",出現次數是：" + maxToal); } /** * 通過String.split("")將字元串直接切割成字元串數組 * @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); } /** * 通過String.toCharArray()將字元串轉為char數組 * @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); }