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Language/Type: Java file processing Scanner
Author: Marty Stepp

Write a method named evaluate that accepts as a parameter a Scanner containing a series of tokens representing a numeric expression involving addition and subtraction and that returns the value of the expression. For example, if a Scanner called data contains the following tokens:

4.2 + 3.4 - 4.1

The call of evaluate(data); should evaluate the result as (4.2+3.4-4.1) = (7.6-4.1) = 3.5 and should return this value as its result. Every expression will begin with a real number and then will have a series of operator/number pairs that follow. The operators will be either + (addition) or - (subtraction). As in the example above, there will be spaces separating numbers and operators. You may assume the expression is legal.

Your method should evaluate operators sequentially from left to right. For example, for this expression:

7.5 - 4.25 - 2.0

Your method should evaluate the operators as 7.5 - 4.25 - 2.0 = (7.5 - 4.25) - 2.0 = 3.25 - 2.0 = 1.25 .

The Scanner might contain just a number, in which case your method should return that number as its result.

Type your solution here:

This is a method problem. Write a Java method as described. Do not write a complete program or class; just the method(s) above.

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