Hi Nan,
Are you using CERR by chance? I had this exact problem when I switched to 2015a and it turned out that MATLAB and CERR both have a function named 'strsplit.m'. MATLAB is unknowingly calling on CERR's version instead.
I fixed this by renaming CERR's strsplit to something else.
If you're not using CERR, check if you have any outside functions using these names:
builtin
strjoin
strsplit
MATLAB has its own internal functions using these. Any outside functions with the same name would cause the error you see.
Hope that helps.
Dan
