Checking empty string in Java

You could try :

if (str[i] == null || str[i].trim().equals("")){
// your code
}

You can use the Apache Commons Lang to check a String:

if (StringUtils.isBlank(str[i]) {
    ...
}

StringUtils.isBlank is checking if the String is null or empty (i.e. if it is equals to "" when all blank characters are removed).