Using java.util.hashtable

This is what I have for code:

sheetName='Sheet2';
[numbers, strings] = xlsread('TestSheet.xlsx', sheetName);
strings(1,:) = [];
strings(:,2) = [];
strings = char(strings);
strings;

phone_book = java.util.Hashtable;  

for i=1:size(strings,1)
    c2 = sprintf('%s',strings(i,:)); 
    n2=numbers(i,1);
    phone_book.put(c2,n2);
end

c3 = 'EXAS';
phone_number    = phone_book.get(char(c3))

And the contents of TestSheet.xlsx are:

symbol openingsize SIMO 2950 PVTB 1639 CBRX 2419 AFFY 2401 VRUS 3868 ARAY 2824 BMTI 2155 ROIAK 2691 CNQR 1357 EXAS 2956

When I try to read number corresponding to EXAS I get []. Where is the problem?