Java oop：查找字符"a"在字符串"What happend today"中出现的次数

//构建一个java程序，查找字符"a"在字符串"What happend today"中出现的次数。

package a;

public class Student{

public static void main(String[] args) {

String str="What happend today";

int times = searchstr("a", str); //返回2

System.out.println("字符a在字符串What happend today中出现的次数:"+times); /*times就是次数的意思*/

}

public  static  int   searchstr(String key/*要搜索的关键词*/, String str/*字符串*/) {

int index = 0;//每次的搜索到的下标

int count = 0;//计数器

while (( index=str.indexOf(key, index)) != -1) {

index = index + key.length()/*关键词的长度*/;

count++;

}

return count; /*没void就要写return，这是规定*/

    }

}