如果我在java中使用模式和匹配器，如何找到匹配数？

i have the following code

我有以下代码

    Pattern keyPattern = Pattern.compile(key);
    Matcher matcher = keyPattern.matcher(str);
    return matcher.replaceAll(value);

this will replaces the key in the str with value; but i want to know how many instances of key's has been replaced with value. so how to know that?

这将用str替换str中的键;但我想知道有多少个密钥实例被替换为值。那怎么知道呢?

2 个解决方案

#1

You can use the find method in a loop to count. There is an example in the Java tutorial:

您可以在循环中使用find方法进行计数。 Java教程中有一个例子:

import java.util.regex.Pattern;
import java.util.regex.Matcher;

public class MatcherDemo {

    private static final String REGEX = "\\bdog\\b";
    private static final String INPUT = "dog dog dog doggie dogg";

    public static void main(String[] args) {
       Pattern p = Pattern.compile(REGEX);
       Matcher m = p.matcher(INPUT); // get a matcher object
       int count = 0;
       while(m.find()) {
           count++;
           System.out.println("Match number "+count);
           System.out.println("start(): "+m.start());
           System.out.println("end(): "+m.end());
       }
    }
}

While you are calling find, you can at the same time collect the parts of the string and manually build the result in a StringBuffer. Or if performance is not an issue, you can first count and then afterwards scan the string again with replaceAll.

当您调用find时,您可以同时收集字符串的部分并在StringBuffer中手动构建结果。或者,如果性能不是问题,您可以先计算,然后再使用replaceAll扫描字符串。

#2

instead you could do:

相反,你可以这样做:

int num = 0;
Pattern keyPattern = Pattern.compile(key);
Matcher matcher = keyPattern.matcher(str);
while(matcher.find()){
    str = matcher.replaceFirst();
    matcher = keyPattern.matcher(str); //don't know if this line is necessary
    num++;
}

#1