How to evaluate string that have exponential

问题:

Javax ScriptEngine and JEval works similarly, you input an string and send it to be evaluated, and it will return you the result of it:

In ScriptEngine (almost the same in JEval):

System.out.println(engine.eval("2*3+4"));

will result in:

10.0

But when I try to make it an exponential:

System.out.println(engine.eval("2^3+4"));

will result in:

5.0

But it really should result in 12 (2^3 = 8, 8+4=12), so my question is how can I set it up in a way that the string which the will be all the whole equation, will evaluate supporting the exponential, and result correctly?

Should I use another library?

回答1:

^ is the XOR operand, your string means 2 XOR 3 + 4, which in facts evaluates to 1 + 4.

You have to use

Math.pow(2,3) + 4

This is my code:

System.out.println(engine.eval("Math.pow(2,3) + 4"));

Output:

12.0