Reading Variables And Their Values From Files?

So here is my code:

while (key != 3) {
if (key == 2) {
System.out.println("Input from a file");
// System.out.print("Enter file name: ");
// String str = expression.nextLine();
int i = 0;
File file = new File(

[code]....

What I need to happen is the file gets read in, the file is in the form:

a * ( b + c ) / 2 + ( 8 * b )
a = 5
b = 10
c = 20
( x + y ) * z
x = 13
y = 21
z = 3

And so on. My code is supposed to start at the beginning and have output like:

Infix: a * b ( b + c ) / 2 + ( 8 * b )
variable values:
a = 5
b = 10
c = 20

**It then needs to store the variable names along with their values in a hash table**

postfix: a b c + * 2 / 8 b * +
value: 155

And it continues reading the file in the same fashion.

My issue is I am not properly extracting the variables and their values from the file. I have the variables in an array list actually, so I have those, but don't know how to efficiently navigate to the values, then store the character and value in a hash table, while protecting against possible blank lines within the file. Thus just calling nextLine()s and next()s wouldn't work to get to values because they would lead to an error.