JavaSe 统计字符串中字符出现的次数
public static void main(String[] args) { // 1、字符串 String str = "*Constructs a new <tt>HashMap</tt> with the same mappings as the * specified <tt>Map</tt>. The<tt>HashMap</tt> is created with default load factor (0.75) and aninitial capacity sufficient to*hold the mappings in the specified<tt>Map</tt>."; // 2.把字符串转换为数组 char[] charArr = str.toCharArray(); // 3.创建一个Map Map<Character, Integer> counterMap = new HashMap<Character, Integer>(); // 4.遍历一个Map for (int i = 0; i < charArr.length; i++) { // 5.拿到的字符作为键到集合中去找值 Integer value = counterMap.get(charArr[i]); if (value == null) { // 把字符作为键,1为值存入集合 counterMap.put(charArr[i], 1); } else { // 把值加1重新写入集合 value += 1; counterMap.put(charArr[i], value); } } Set<Map.Entry<Character, Integer>> entrySet = counterMap.entrySet(); for (Map.Entry<Character, Integer> entry : entrySet) { System.out.println(entry.getKey() + " 字符出现次数=" + entry.getValue()); } }