Why do I receive an error when I call the "read" method of the FileInputStream in MATLAB?

When I call the "read" method of the FileInputStream in MATLAB while running the following commands:

myFile = java.io.FileInputStream('dummyfile.txt');

b = javaArray ('java.lang.Byte',5)

myFile.read(b)

I receive the error:

 ??? No method read with matching signature found for class java.io.FileInputStream

Based on the java doc for the java.io.FileInputStream, the read method can take a byte[] input:

int read(byte[] b)

Answer 1

[MathWorks Support Team]

This error is due to the lack of support for primitive Java data types in MATLAB. The "read" method of the FileInputStream class in the java.io package actually expects an array of primitive bytes (byte[]) and not an array of the Byte wrapper object (java.lang.Byte[]).

As a work around, you can use the overloaded read method that does not take any input arguments within a loop:

 myFile = java.io.FileInputStream('dummyfile.txt');

 b = zeros(1,myFile.available);

 for n = 1:length(b)

    b(n) = myFile.read;

 end

In order to use a function such as this in this manner, you would need to declare the function as follows:

int read(java.lang.Byte[] b)