java.io.File - strange behaviour

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bbb_bbb
bbb_bbb 2018-12-29
评论： John 2019-5-17
filename='F:\__1\2\test files\file.bin';
success=java.io.File(filename).delete;
invoked from the Matlab Command Window - works,
running as a script - gives error:
"Static method or constructor invocations cannot be indexed.
Do not follow the call to the static method or constructor with any additional indexing or dot references.
MATLAB:staticMethodIndex"
Why is this so?

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Yair Altman
Yair Altman 2018-12-30
With most Java methods, you can follow the method invocation parentheses with a dot, thereby chaining methods. For example: myJPanel.getComponent(0).getComponent(1).setVisible(false). However, such method chaining cannot be done with a constructor - it's valid syntax in Java, but Matlab's interpreter is not smart enough. In this case, simply separate the call into two parts:
filename='F:\__1\2\test files\file.bin';
jFile = java.io.File(filename);
success = jFile.delete;
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Yair Altman
Yair Altman 2019-5-17
as far as I am aware, the behavior is the same in this regards in both the command window and scripts - in both cases you cannot chain methods to a Java constructor call, only to other methods.
John
John 2019-5-17
Nope, they are different. I just tested:
>> ls('D:\tmp')
Figure1.JPG
Figure2.JPG
>> filename = 'D:\temp\Figure1.JPG';
>> success=java.io.File(filename).delete
success =
logical
0
Put those exact lines into a script? and get:
>> Untitled7
Error: Functions cannot be indexed using {} or . indexing.
Error in Untitled7 (line 2)
success=java.io.File(filename).delete;
Conclusion: The parser in the command line, is different from the parser, that parses scripts... That's a bit of a surprise to me, but I'm not into the details of Matlab like you are.

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