如何计算序列在Java字符串中出现的次数？

Question

我有一个看起来像这样的字符串:

"Hello my is Joeseph. It is very nice to meet you. What a wonderful day it is!". 

我想计算is字符串中的次数.

我怎么能用Java做到这一点？

Answer 1

一种简单的方法是使用Apache StringUtils countMatches

StringUtils.countMatches("Hello my is Joeseph. It is very nice to meet you. What a wonderful day it is!", "is");

Answer 2

int index = input.indexOf("is");
int count = 0;
while (index != -1) {
    count++;
    input = input.substring(index + 1);
    index = input.indexOf("is");
}
System.out.println("No of *is* in the input is : " + count);