如何解析以字符串形式给出的数学表达式并返回一个数字? [英] How to parse a mathematical expression given as a string and return a number?

问题描述

Java 中有没有办法从这个数学表达式中得到结果:

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

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

另一方面，解析算术表达式的最佳方法是什么?

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

推荐答案

您可以将其传递给 BeanShellbsh.Interpreter，类似这样:

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"));

您需要确保您评估的字符串来自受信任的来源和通常的预防措施，否则它会立即起作用.

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.

如果您想采用更复杂(但更安全)的方法，您可以使用 ANTLR(我怀疑以数学语法为起点)并实际编译/解释语句.

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.

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