[待更新]java基础常用文件操作

打印当前项目路径

System.getProperty("user.dir")
// 这是项目根目录路径&＃xff0c;下级路径要自己写

获取文件的上级目录

import java.io.File;public class DirSize {public static void main(String[] args) {File dir &＃61; new File("/home/huanyu/Desktop");String parentPath &＃61;dir.getParent();System.out.println("该目录的上级目录为&＃xff1a;"&＃43;parentPath);}
}


获取路径分隔符

windows和linux是不同的。

String a &＃61; System.getProperty("file.separator");

读取文件

FileInputStream方式&＃xff1a;常用

FileInputStream fis &＃61; new FileInputStream(filePath); // filePath是自定义路径str
// 指定编码格式
BufferedReader br &＃61; new BufferedReader(new InputStreamReader(fis, "utf-8"));
String line &＃61; null;
while ((line &＃61; br.readLine()) !&＃61; null) {System.out.println(line);//break;
}
fis.close();

Stream方式&＃xff1a;可以带函数处理

//1. filter line 3
//2. convert all content to upper case
//3. convert it into a List
list &＃61; stream.filter(line -> !line.startsWith("line3")).map(String::toUpperCase).collect(Collectors.toList());//不处理&＃xff0c;指定编码的话
Charset c &＃61; Charset.forName("UTF-8");
//System.out.println(Charset.isSupported("UTF-8"));
try(Stream<String> stream &＃61; Files.lines(Paths.get(filePath), c)) {List<String> raws &＃61; new ArrayList<>();raws &＃61; stream.collect(Collectors.toList());for (String s:raws) {System.out.println(s);}
} catch(IOException e) {e.printStackTrace();
}