标准字符集常量定义类：
StandardCharsets.UTF_8
获取文件路径：
System.out.println(System.getProperty("user.dir"));
/*结果：D:\IdeaProjectsMe\project-task*/
image.png
Application.class.getClassLoader().getResourceAsStream("rpc.properties")
或
Thread.currentThread().getContextClassLoader().getResourceAsStream("application.yml");、
/*结果：D:\IdeaProjectsMe\argus-task*/
image.png
//获取绝对路径
System.out.println(Application.class.getProtectionDomain().getCodeSource().getLocation().getFile());
image.png
Read
读取yml文件：
InputStream is = null; try { is = Thread.currentThread().getContextClassLoader().getResourceAsStream("application.yml"); Yaml yaml = new Yaml(); String result = yaml.dumpAsMap(yaml.load(is)); //... }result内容如下：
image.png
Java循环读取txt文本中的一行（findBug可能出现Reliance on default encoding风险）
try {
File file = new File("D:\\PythonWorkspace\\ReportData\\" + ramp_alarm_filename);
BufferedReader bufferedReader = new BufferedReader(new FileReader(file));
String line;
while ((line = bufferedReader.readLine()) != null) {
String[] lines = line.split("\t");
}
} catch (Exception e) {
}
读取JSON文件
package com.idss.liaoning.utils;
import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;
import org.apache.commons.io.FileUtils;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import java.io.File;
/**
* 读取json文件
*/
public class ReadJsonUtil {
private static final Logger LOGGER = LogManager.getLogger(ReadJsonUtil.class.getName());
/**
* 读取 JSONObject
*
* @param fileName 文件名
* @return JSONObject
*/
public static JSONObject readJsonObject(String fileName) {
try {
File file = new File(System.getProperty("user.dir") + "/json/liaoning/manage/" + fileName);
String content = FileUtils.readFileToString(file, "UTF-8");
return JSONObject.parseObject(content);
} catch (Exception e) {
e.printStackTrace();
LOGGER.error(e.getMessage());
return new JSONObject();
}
}
/**
* 读取 JSONArray
*
* @param fileName 文件名
* @return JSONArray
*/
public static JSONArray readJsonArray(String fileName) {
try {
File file = new File(System.getProperty("user.dir") + "/json/liaoning/manage/" + fileName);
String content = FileUtils.readFileToString(file, "UTF-8");
return JSONArray.parseArray(content);
} catch (Exception e) {
e.printStackTrace();
LOGGER.error(e.getMessage());
return new JSONArray();
}
}
}
读取properties文件
properties文件：
loginUrl=http://127.0.0.1
loginName=root
loginPwd=123456
verifyCode=aaaa
读取properties
package com.idss.liaoning.utils;
import java.io.InputStream;
import java.util.Map;
import java.util.Properties;
import java.util.concurrent.ConcurrentHashMap;
/**
* 常量类
*/
public class Constant {
public static final ConcurrentHashMap propertiesMap;
public static final String loginUrl;
public static final String loginName;
public static final String loginPwd;
public static final String verifyCode;
static {
try {
InputStream inStream = Constant.class.getClassLoader().getResourceAsStream("element.properties");
Properties prop = new Properties();
//此处避免使用prop.load(FileInputStream)从而导致的读取中文乱码问题;
//尽量使用prop.load(FileReader)或指定字符集的Stream
InputStreamReader inputStreamReader = new InputStreamReader(inStream, StandardCharsets.UTF_8);
prop.load(inputStreamReader);
propertiesMap = new ConcurrentHashMap((Map)prop);
loginUrl = propertiesMap.get("loginUrl");
loginName = propertiesMap.get("loginName");
loginPwd = propertiesMap.get("loginPwd");
verifyCode = propertiesMap.get("verifyCode");
} catch (Exception e) {
e.printStackTrace();
throw new RuntimeException(e);
}
}
}
Write
写文件换行
new FileOutputStream(file, true) 第二个参数为追加
/**
* 写文件
*/
public static boolean modifyEmailProperties() {
OutputStreamWriter outputStreamWriter = null;
BufferedWriter bufferedWriter = null;
try {
File file = new File("D:\\test//test.txt");
outputStreamWriter = new OutputStreamWriter(new FileOutputStream(file, true), StandardCharsets.UTF_8);
bufferedWriter = new BufferedWriter(outputStreamWriter);
bufferedWriter.newLine();
bufferedWriter.write("==========");
bufferedWriter.flush();
return true;
} catch (IOException e) {
logger.error("文件找不到.......", e);
return false;
} finally {
if (bufferedWriter != null) {
try {
bufferedWriter.close();
} catch (IOException e) {
logger.error("修改配置信息文件 bufferedWriter.close 异常.......", e);
}
}
if (outputStreamWriter != null) {
try {
outputStreamWriter.close();
} catch (IOException e) {
logger.error("修改配置信息文件 outputStreamWriter.close 异常.......", e);
}
}
}
}
java修改文件的多行内容
思路：
1、将文件内容一行一行的读出来
2、在每读一行的时候，判断是否以a或b开始，如果是则进行处理，然后写到缓冲对象。如果不是则直接写入缓冲对象中
3、将缓冲对象中的内容回写到文件中完整代码如下：
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
/**
* 修改文件
*/
public class FileModify {
/**
* 读取文件内容
*
* @param filePath
* @return
*/
public String read(String filePath) {
BufferedReader br = null;
String line = null;
StringBuffer buf = new StringBuffer();
try {
// 根据文件路径创建缓冲输入流
br = new BufferedReader(new FileReader(filePath));
// 循环读取文件的每一行, 对需要修改的行进行修改, 放入缓冲对象中
while ((line = br.readLine()) != null) {
// 此处根据实际需要修改某些行的内容
if (line.startsWith("a")) {
buf.append(line).append(" start with a");
}
else if (line.startsWith("b")) {
buf.append(line).append(" start with b");
}
// 如果不用修改, 则按原来的内容回写
else {
buf.append(line);
}
buf.append(System.getProperty("line.separator"));
}
} catch (Exception e) {
e.printStackTrace();
} finally {
// 关闭流
if (br != null) {
try {
br.close();
} catch (IOException e) {
br = null;
}
}
}
return buf.toString();
}
/**
* 将内容回写到文件中
*
* @param filePath
* @param content
*/
public void write(String filePath, String content) {
BufferedWriter bw = null;
try {
// 根据文件路径创建缓冲输出流
bw = new BufferedWriter(new FileWriter(filePath));
// 将内容写入文件中
bw.write(content);
} catch (Exception e) {
e.printStackTrace();
} finally {
// 关闭流
if (bw != null) {
try {
bw.close();
} catch (IOException e) {
bw = null;
}
}
}
}
/**
* 主方法
*/
public static void main(String[] args) {
String filePath = "C:/file.txt"; // 文件路径
FileModify obj = new FileModify();
obj.write(filePath, obj.read(filePath)); // 读取修改文件
}
}