How to parse a mathematical expression given as a

Question

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• How to evaluate a math expression given in string form? [closed] 24 answers

Is there a way in Java to get the result from this mathematical expression:

String code = "5+4*(7-15)";

In other hand what's the best way to parse an arithmetic expression?

Answer 1

There is no direct support in the Java SDK for doing this.

You will either have to implement it yourself (possibly using a parser generator such as JavaCC), or use an existing library.

One option would be JEP (commercial), another JEval (free software).

Answer 2

Probably not in as straight forward a manner as you are hoping!

But perhaps you could use a javax.script.ScriptEngine and treat the string as a ECMAScript expression, for example?

Take a look at: Scripting for the Java Platform.

Answer 3

There is no builtin way of doing that. But you can use one of the many many open source calculators available.

Answer 4

You can pass it to a BeanShell bsh.Interpreter, something like this:

Interpreter interpreter = new Interpreter();
interpreter.eval("result = 5+4*(7-15)");
System.out.println(interpreter.get("result"));

You'll want to ensure the string you evaluate is from a trusted source and the usual precautions but otherwise it'll work straight off.

If you want to go a more complicated (but safer) approach you could use ANTLR (that I suspect has a math grammar as a starting point) and actually compile/interpret the statement yourself.

Answer 5

You coul use that project

How to use:

double result = 0;
String code = "5+4*(7-15)";
try {
    Expr expr = Parser.parse(code);
    result = expr.value();
} catch (SyntaxException e) {
    e.printStackTrace();
}
System.out.println(String.format("Result: %.04f", result));

Answer 6

There's a commercial tool called formula4j that does that job.

To take your example expression, it would be evaluated like this using formula4j:

Formula formula = new Formula("5+4*(7-15)");

Decimal answer = formula.getAnswer(); //-27