Evaluating a math expression in Java.

Question

I wanted to see how a programmer can evaluate a math expression in Java, such as this:
input:
10^6
8+5+6
152.53-6*(5)

output:
1000000
19
122.53

However, I wanted to avoid too many if or switch statements, and avoid putting spaces between the values and the operands.

How can I do such?

Answer 1

@Timon Paßlick

Because I made a code in which was basic calculator, yet I got complaints and downvotes based on if and switch statements, plus putting spaces between the operands and the numbers. Especially considering the fact that you could only evaluate 2 numbers at a time, I felt pretty badly about the code.

https://code.sololearn.com/c6onX1jZFliG/#java

If and/or switch statements are a given, but I don't want the whole program to just be switch after switch after switch after switch, proving to be a useless calculator.

Although I don't think there's much wrong with it, I would like to learn how to do more advanced coding, and learning how to evaluate a math expression is part of it.

Answer 2

https://stackoverflow.com/questions/3422673/evaluating-a-math-expression-given-in-string-form?utm_medium=organic&utm_source=google_rich_qa&utm_campaign=google_rich_qa

Answer 3

Why do you have fear of if and switch?

Answer 4

Sheldon Duncan Advanced coding is also with if and switch, no idea why they downvoted.

Answer 5

Operator precedence is important.

4 + 5 * 10 = 54, and not 90

Answer 6

I think the original poster is talking about parsing a mathematical expression, and then evaluating it. You normally use a tree for for this.