如何使用相对路径而不是绝对路径？

Question

So I am having a strange issue with Java.

I'm reading a writing files, so the path is important to me. I would like all files to be written and read from the relative path (ie in the folder with the rest of my class and java files).

I write files like so:

FileWriter fw = new FileWriter(outfile,true);
fw.write(data);
fw.close();

where outfile is something like 'out.txt' (ie the name of the file we want the output to go in).

The problem is, the file is created in /home/me/ instead of the path of my other files.

Am i doing something wrong? Or how can i get the files stored in the relative directory?

Answer 1

FileWriter fw = new FileWriter("./" + outfile,true);

or

FileWriter fw = new FileWriter("~/" + outfile,true);

I would try that.

Answer 2

The working directory is where you run the program from ie where you call java YourClass, so when you want to write files relative to the class that's executing you'll have to know the current directory and append the relative path from there eg

So if you have a class test.YourClass and you run the application from the source root ie

java test.YourClass

you can find the absolute path to the directory your class file is in from the the user.dir system property and the classes package name as follows:

public class YourClass {

public void printPath() {
    String path = String.format("%s/%s", System.getProperty("user.dir"), this.getClass().getPackage().getName().replace(".", "/"));
    System.out.println(path);
}

}

Answer 3

Java will save files relative to the current working directory. Are you inside you home directory when you run the program?

If you always want files to be saved relative to the location of the Java files and not the current working directory, you need to find that directory and prepend it to get an absolute path.

Answer 4

在命令行上设置user.dir属性，或者只是从你想要的所有目录运行（通过cd-ing）