如何解析作为字符串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

  String code =5 + 4 * （7-15）; 
  

另一方面，解析算术表达式的最佳方式是什么？

解决方案

您可以将其传递给 BeanShell bsh.Interpreter ，如下所示：

 口译翻译=新翻译（）; 
 interpreter.eval（result = 5 + 4 *（7-15））; 
 System.out.println（interpreter.get（result））; 
  

您需要确保评估的字符串来自受信任的来源和通常的注意事项，否则它将直接工作。

如果你想要一个更复杂（但更安全）的方法，你可以使用 ANTLR （我怀疑以数学语法为起点），实际上是自己编译/解释这个陈述。

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?

解决方案

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.

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