统计一个字符串中每一个字符出现的次数
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);
}
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