字符串中子字符串的出现次数 [英] Occurrences of substring in a string

问题描述

为什么下面的算法对我没有停止?(str 是我要搜索的字符串，findStr 是我要查找的字符串)

Why is the following algorithm not halting for me? (str is the string I am searching in, findStr is the string I am trying to find)

String str = "helloslkhellodjladfjhello";
String findStr = "hello";
int lastIndex = 0;
int count = 0;

while (lastIndex != -1) {
    lastIndex = str.indexOf(findStr,lastIndex);

    if( lastIndex != -1)
        count++;

    lastIndex += findStr.length();
}

System.out.println(count);

推荐答案

最后一行产生了一个问题.lastIndex 永远不会是 -1，所以会有一个无限循环.这可以通过将最后一行代码移到 if 块中来解决.

The last line was creating a problem. lastIndex would never be at -1, so there would be an infinite loop. This can be fixed by moving the last line of code into the if block.

String str = "helloslkhellodjladfjhello";
String findStr = "hello";
int lastIndex = 0;
int count = 0;

while(lastIndex != -1){

    lastIndex = str.indexOf(findStr,lastIndex);

    if(lastIndex != -1){
        count ++;
        lastIndex += findStr.length();
    }
}
System.out.println(count);

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