java - 正则表达式同时显示不同的返回不同的结果

Question

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

public class Validate {

    public static void main(String[] args) {

        Matcher matcher;
        Pattern regex;
        String str="David";
        regex =Pattern.compile("^[A-Za-z]*$", Pattern.CASE_INSENSITIVE);
        matcher= regex.matcher(str);
        System.out.println("First result="+matcher.find());  //true
        System.out.println("Second result="+matcher.find()); //false

    }
}

Answer 1

摘自Matcher.find()的API文档

Attempts to find the next subsequence of the input sequence that matches the pattern.

This method starts at the beginning of this matcher's region, or, if a previous invocation of the method was successful and the matcher has not since been reset, at the first character not matched by the previous match.

If the match succeeds then more information can be obtained via the start, end, and group methods.

因此，要运行代码，您必须先调用 Matcher.reset()，然后再调用 Matcher.find()。