Java 读取文件最后N行数快速实现

引入 common-io

    commons-io
    commons-io
    2.2

import org.apache.commons.io.input.ReversedLinesFileReader;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class ReverseFileReadTest {

    private static List readLastLines(File file, int lineNum) {
        List result = new ArrayList<>();
        try (ReversedLinesFileReader reader = new ReversedLinesFileReader(file)) {
            String line = "";
            while ((line = reader.readLine()) != null && result.size() < lineNum) {
                result.add(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        Collections.reverse(result);
        return result;
    }

    public static void main(String[] args) {
        // 读取log.json 最后100行
        readLastLines(new File("/data/log.json"), 100);
    }
}