How to use java.nio in MATLAB?

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bbb_bbb 2018-12-26

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https://ww2.mathworks.cn/matlabcentral/answers/437249-how-to-use-java-nio-in-matlab

评论： bbb_bbb 2018-12-30

采纳的回答： Kojiro Saito

在 MATLAB Online 中打开

How to delete a file using this method in MATLAB?

https://docs.oracle.com/javase/7/docs/api/java/nio/file/Files.html#delete(java.nio.file.Path)

like this, but using NIO instead of IO:

java.io.File(filename).delete()

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Answer 1

Kojiro Saito 2018-12-27

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https://ww2.mathworks.cn/matlabcentral/answers/437249-how-to-use-java-nio-in-matlab#answer_354063

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Here is two example of deleting a file using java.nio.file.

%% Method1
str = fullfile(pwd, 'test1.txt' );
%jpath1 = java.nio.file.Paths.get(str) % not works
jpath1 = java.nio.file.Paths.get(str, javaArray('java.lang.String', 0)); % works
java.nio.file.Files.delete(jpath1)
%% Method2
jpath2 = java.nio.file.Paths.get(pwd, 'test2.txt');
java.nio.file.Files.delete(jpath2)

I've tested in MATLAB R2018b on Windows 10.

As you may know, from R2017b, MATLAB's JVM was changed to Java 8. So, java.nio.file.Files.delete used in MATLAB R2017b ~ R2018b is that of Java 8.

https://docs.oracle.com/javase/8/docs/api/java/nio/file/Files.html#delete-java.nio.file.Path-

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bbb_bbb 2018-12-27

编辑：bbb_bbb 2018-12-27

在 MATLAB Online 中打开

Thank you.

java.nio.file.Files is also part of Java 7, which is available in MATLAB R2013b (8.2) or newer. I use R2015.

Method2 works, but Method1 does not:

str = fullfile(pwd, 'test1.txt' );
jpath1 = java.nio.file.Paths.get(str, javaArray('java.lang.String', 0))

Error using javaArray

All dimension arguments must be greater than zero

The problem is that before I used

java.io.File(['\\?\' filename]).delete

where filename is full file name (e.g. 'C:\myfiles\test1.txt'),

and it worked fine.

That UNC-path prefix ('\\?\') was used to work with unusual files which are not processed by conventional methods (with specific characters in their names).

If I use the Method2 with that pathname:

jpath2 = java.nio.file.Paths.get(['\\?\' pwd], 'test2.txt')

Java exception occurred:

java.nio.file.InvalidPathException: Illegal character [?] in path at index 2: \\?\C:\myfiles\test2.txt

at sun.nio.fs.WindowsPathParser.nextSlash(Unknown Source)

at sun.nio.fs.WindowsPathParser.parse(Unknown Source)

at sun.nio.fs.WindowsPath.parse(Unknown Source)

at sun.nio.fs.WindowsFileSystem.getPath(Unknown Source)

at java.nio.file.Paths.get(Unknown Source)

So, is there any way to use UNC-path with java.nio?

What is the problem with Method1 that you proposed?

Kojiro Saito 2018-12-29

在 MATLAB Online 中打开

>> Btw, how to determine the success of the operation:

I would simply use "try catch".

try
    java.nio.file.Files.delete(jpath2)
catch ME
    % When delete was failed, do some error handle
    error(ME.message)
end
% When delete was successful
msgbox('Successfully deleted')