假设给你一个日志文件，需要找到拥有 Error 关键信息的行，然后输出该行内容和行号。错误日志内容：
29-May-2023 11:06:53.541 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log Server version: Apache Tomcat/8.5.32 29-May-2023 11:06:53.545 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log Server built: Jun 20 2018 19:50:35 UTC 29-May-2023 11:06:53.546 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log Server number: 8.5.32.0 29-May-2023 11:06:53.547 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log OS Name: Windows 8.1 29-May-2023 11:06:53.547 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log OS Version: 6.3 29-May-2023 11:06:53.547 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log Architecture: amd64 29-May-2023 11:06:53.547 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log Java Home: D:\ProgramFilesFree\Java\jdk1.8.0_45\jre 29-May-2023 11:06:53.548 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log JVM Version: 1.8.0_45-b15 29-May-2023 11:06:53.548 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log JVM Vendor: Oracle Corporation 29-May-2023 11:06:53.548 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log CATALINA_BASE: D:\server\tomcat-8.5.32 29-May-2023 11:06:53.548 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log CATALINA_HOME: D:\server\tomcat-8.5.32 ... 29-May-2023 11:07:30.463 信息 [Finalizing set up] jenkins.install.SetupWizard.init 29-May-2023 11:07:31.011 信息 [Download metadata thread] hudson.util.Retrier.start Calling the listener of the allowed exception 'sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target' at the attempt #1 to do the action check updates server 29-May-2023 11:07:31.026 信息 [Download metadata thread] hudson.util.Retrier.start Attempted the action check updates server for 1 time(s) with no success 29-May-2023 11:07:31.049 严重 [Download metadata thread] hudson.PluginManager.doCheckUpdatesServer Error checking update sites for 1 attempt(s). Last exception was: SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target 29-May-2023 11:07:31.095 信息 [Download metadata thread] hudson.model.AsyncPeriodicWork.lambda$doRun$0 Finished Download metadata. 1,384 ms 29-May-2023 11:07:31.096 信息 [Jenkins initialization thread] hudson.WebAppMain$3.run Jenkins is fully up and running
方式一：使用 BufferedReader 类，每次读取一行，通过一个 lineNumber 记录行号，每读取一行，lineNumber 加一，如下：
package com.hxstrive.java_io.example;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
public class LogErrorSearch {
public static void main(String[] args) {
String logFilePath = "error.log"; // 替换为实际的日志文件路径
try (BufferedReader reader = new BufferedReader(new FileReader(logFilePath))) {
String line;
int lineNumber = 0;
while ((line = reader.readLine()) != null) {
lineNumber++;
if (line.contains("Error")) {
System.out.println("错误信息在第 " + lineNumber + " 行：");
System.out.println(line);
}
}
} catch (IOException e) {
System.err.println("读取日志文件时发生错误：" + e.getMessage());
}
}
}运行输出：
错误信息在第 64 行： 29-May-2023 11:07:31.049 严重 [Download metadata thread] hudson.PluginManager.doCheckUpdatesServer Error checking update sites for 1 attempt(s). Last exception was: SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
方式二：使用 LineNumberReader 类来实现，如下：
package com.hxstrive.java_io.example;
import java.io.FileReader;
import java.io.IOException;
import java.io.LineNumberReader;
public class LogErrorSearchWithLineNumberReader {
public static void main(String[] args) {
String logFilePath = "error.log"; // 需替换为实际的日志文件路径
try (LineNumberReader reader = new LineNumberReader(new FileReader(logFilePath))) {
String line;
while ((line = reader.readLine()) != null) {
if (line.contains("Error")) {
int lineNumber = reader.getLineNumber();
System.out.println("错误信息在第 " + lineNumber + " 行：");
System.out.println(line);
}
}
} catch (IOException e) {
System.err.println("读取日志文件时出现错误：" + e.getMessage());
}
}
}运行效果和方式一一致。
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