Python工程师Java之路（k）文件读写

1、Java版

1.1、获取本类信息：this.getClass

package a.b.c;

public class Hello {
    public static void main(String[] args) {
        (new Hello()).getThisClass();
    }

    private void getThisClass() {
        Class c = this.getClass();

        System.out.println(c);
        // class a.b.c.Hello

        System.out.println(c.getSimpleName());
        // Hello

        System.out.println(c.getName());
        // a.b.c.Hello

        System.out.println(c.getTypeName());
        // a.b.c.Hello

        System.out.println(c.getPackage());
        // package a.b.c

        System.out.println(c.getResource("/"));
        // file:/C:/Users/yellow/IdeaProjects/JavaProject/out/production/JavaProject/

        System.out.println(c.getResource(""));
        // file:/C:/Users/yellow/IdeaProjects/JavaProject/out/production/JavaProject/a/b/c/

        System.out.println(c.getResource("").getPath());
        // /C:/Users/yellow/IdeaProjects/JavaProject/out/production/JavaProject/a/b/c/
    }
}

1.2、文件：File

File f = new File("JavaProject.iml");
// 文件字节数
f.length();
// 是否存在这个文件
f.exists(); // true
// 是否是文件
f.isFile(); // true
// 是否文件夹
f.isDirectory();
// 绝对路径
f.getAbsolutePath(); // C:\Users\yellow\IdeaProjects\JavaProject\JavaProject.iml
// 文件名
f.getName(); // JavaProject.iml
// 是否绝对路径
f.isAbsolute(); // false

一些其它方法

createNewFile ：当且仅当具有该名称的文件尚不存在时，创建一个新的空文件
delete ：删除由此File表示的文件或目录。只能删除空目录
mkdir ：创建由此File表示的目录
list ：返回一个String数组，表示该File目录中的所有子文件或目录
listFiles ：返回一个File数组，表示该File目录中的所有的子文件或目录。

1.2.1、递归打印目录树

import java.io.File;

public class Hello {
    public static void main(String[] args) {
        Hello hello = new Hello();
        hello.tree("C:\\Users\\yellow\\IdeaProjects\\javaSE");
        hello.tree("C:\\Users\\yellow\\IdeaProjects\\javaSE\\javaSE.iml");
        hello.tree("C:/Users/yellow/IdeaProjects/javaSE");
        hello.tree("/");
    }

    public void tree(File rootDir) {
        System.out.println(rootDir);
        if (rootDir.isDirectory()) {
            File[] files = rootDir.listFiles();
            if (files != null) {
                for (File file : files) {
                    tree(file);
                }
            }
        }
    }

    public void tree(String fileName) {
        tree(new File(fileName));
    }
}

1.2.2、文件名拼接+获取同级目录文件全名（还没验证Maven安装后的）

1.2.2.1、待验

import java.io.File;

public class Dict {
    public static void main(String[] args) {
        Dict d = new Dict();
        File f = d.getLateralFile("dict.txt");
        System.out.println(f);
        System.out.println(f.isFile());
        System.out.println(f.exists());
    }

    // 获取平级文件
    public File getLateralFile(String child) {
        String parent = this.getClass().getResource("").getPath();
        return new File(parent, child);
    }
}

1.2.2.2、Maven安装后，别的工程导入依赖可用（已初验，未报错）

BufferedReader bR = new BufferedReader(new InputStreamReader(
        this.getClass().getResourceAsStream("dict.txt"), StandardCharsets.UTF_8));

1.3、按行读写文件

// 写数据
BufferedWriter bW = new BufferedWriter(new FileWriter("a.txt"));
bW.write("落水无花\n拉");
bW.write("屎无痕\n");
bW.close();
// 读数据（按行）
BufferedReader bR = new BufferedReader(new FileReader("a.txt"));
String line1 = bR.readLine();
String line2 = bR.readLine();
String line3 = bR.readLine();
String line4 = bR.readLine();
System.out.println(line1);
System.out.println(line2);
System.out.println(line3);
System.out.println(line4);
bR.close();

打印结果

2、Scala版

2.1、相对路径读文件

2.2、getClass

println(this.getClass)
// class a.b.c.Hello$

println(this.getClass.getPackage)
// package a.b.c

println(this.getClass.getName)
// a.b.c.Hello$

println(this.getClass.getResource(""))
// file:/C:/Users/yellow/IdeaProjects/mavenP/target/classes/a/b/c/

println(this.getClass.getResource("/"))
// file:/C:/Users/yellow/IdeaProjects/mavenP/target/classes/

println(this.getClass.getResource("").getPath)
// /C:/Users/yellow/IdeaProjects/mavenP/target/classes/a/b/c/

println(this.getClass.getResource("/").getPath)
// /C:/Users/yellow/IdeaProjects/mavenP/target/classes/

2.3、文件名拼接+获取同级目录文件全名（待验）

package a.b.c

import scala.io.{BufferedSource, Source}

object Hello {
  def main(args: Array[String]): Unit = {
    val path:String = this.getClass.getResource("a.txt").getPath
    println(path)
    val bufferedSource: BufferedSource = Source.fromFile(path)
    val wholeText: String = bufferedSource.mkString
    print(wholeText)
  }
}

2.4、按行读取

val path:String = this.getClass.getResource("a.txt").getPath
val bufferedSource: BufferedSource = Source.fromFile(path)
val lines: Iterator[String] = bufferedSource.getLines()
lines.foreach(println)

3、Python版

文件名拼接+获取同级目录文件全名

from os import path

PATH = path.dirname(__file__)  # 当前文件父级目录的绝对路径

def get_absolute_path(file_name, directory_name=PATH):
    return path.join(directory_name, file_name)

def read_lines(file_name):
    with open(file_name, encoding='utf-8') as f:
        return f.read().strip().split('\n')

if __name__ == '__main__':
    print(read_lines(get_absolute_path("a.txt")))