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That is the String from a String array.

Have you tried printing the contents of these arrays: splitNumbers and splitSymbols

System.out.println(Arrays.toString(calcOperators));

Read the API doc for the Array class's toString() method to see what I am talking about.

What is the arg to the toString() method? It needs to be an array, not an ArrayList.
The only arrays I see are: splitNumbers and splitSymbols

You can Print out the contents of an array by using this method:
System.out.println("an ID "+ java.util.Arrays.toString(theArrayName));

Go through the array from the split() and use the techniques listed in post#2 to decide where to copy the value.
Compare the Strings to test for the operators.
parse the Strings to test for...

For the operators you could compare the Strings against the possibilities.
For the operands, you could use a parse method inside a try/catch block to see if the String was a valid number.