在java-BufferedReader行为中计算字符串中的行数

Question

package test;

import java.io.BufferedReader;
import java.io.StringReader;

public class LineCountTest {

    private static final String test = "This is a\ntest string\n\n\n";
    private static final String test2 = "This is a\ntest string\n\n\n ";

    public static void main(String[] args) {
        System.out.println("Line count: " + countLines(test));
        System.out.println("Line count: " + countLines(test2));
    }

    private static int countLines(String s) {
        try (
                StringReader sr = new StringReader(s);
                BufferedReader br = new BufferedReader(sr)
        ) {
            int count = 0;
            for (String line = br.readLine(); line != null; line = br.readLine()) {
                count++;
            }
            return count;
        } catch (Exception e) {
            return -1;
        }
    }

}

String[] lines = s.split("\n", -1);
int count = lines.length;

会给我正确的/预期的行数。我只问性能方面的原因，以及是否有人能判断BufferedReader的行为是否正确。

Answer 1

因此，您发现，当最后一行以\n结尾或非空时，可以识别它。

出于您的目的，可以使用：

String[] lines = "This is a\ntest string\n\n\n".split("\r?\n", 5);

这保证数组将有5个元素。不过，Regex split有点慢。