计算字符串中字符出现次数的简单方法
问题描述：
是否有一种简单的方法（而不是手动遍历所有字符串，或循环遍历indexOf）以便查找字符出现在字符串中的次数？
Is there a simple way (instead of traversing manually all the string, or loop for indexOf) in order to find how many times, a character appears in a string?
假设我们有abdsd3 $ asda $ asasdd $ sadas，我们希望$出现3次。
Say we have "abdsd3$asda$asasdd$sadas" and we want that $ appears 3 times.
答
String s = "...";
int counter = 0;
for( int i=0; i<s.length(); i++ ) {
if( s.charAt(i) == '$' ) {
counter++;
}
}
这绝对是最快的方法。这里的正则表达式要慢得多，而且可能更难理解。
This is definitely the fastest way. Regexes are much much slower here, and possible harder to understand.