Java String来完成数学总和 [英] Java String to complete mathematical sum

问题描述

在java中，我目前正在尝试通过在JTextField中键入文本，将其放入String并将其转换为int并求解来找到一种方法来进行数学求和。但问题是，我不想简单地将数字放入字符串中，而是将实际的总和包括加法，减法等。

In java, I am currently in the process of trying to find a way to do mathematical sums by typing in text to a JTextField, putting it into a String, and converting it to an int and solving. The problem is however, I don't want to simply put a number into the string but an actual sum including addition, subtraction etc.

目前它只接受类似的操作，1将从字符串转换为int，但当我执行'1 + 1'或甚至只是'1+'时，它会抛出异常，因为' +'不是数字。

我已经明白它不会工作因为int只允许数字。

Currently it will accept just doing something like, 1 which will go from string and convert to an int, but when I do '1+1' or even just '1+' it throws exceptions everywhere because '+' isn't a number.
Which I already understand that it wont work because int's only allow numbers.

我有办法吗？安全地在文本字段中输入一个完整的总和并以某种方式将其转换为int？比如输入7-2 * 5然后答案被保存在一个int？

Is there a way I can safely type a complete sum into the text field and convert it to an int somehow? Like typing 7-2*5 and then the answer being held in an int?

谢谢。

推荐答案

您可以使用 JavaScript 引擎：

ScriptEngineManager mgr = new ScriptEngineManager();
ScriptEngine engine = mgr.getEngineByName("JavaScript");
String expression = textField.getText();
System.out.println(engine.eval(expression));

编辑以允许所有公式：

现在你要做的就是允许 sin，cos，tan 这样的事情：

All you have to do now to allow things like sin, cos, tan is this:

ScriptEngineManager mgr = new ScriptEngineManager();
ScriptEngine engine = mgr.getEngineByName("JavaScript");
String expression = textField.getText();

// Between here...
        expression = expression.
                replace("sin", "Math.sin").
                replace("cos", "Math.cos").
                replace("tan", "Math.tan").
                replace("sqrt", "Math.sqrt").
                replace("log", "Math.log").
                replace("pi", "Math.PI");
// And so on...

System.out.println(engine.eval(foo));

那么你可以这样做：

5 + 5 - 2 / 5 + sin(55) - log(20)

你想要的任何东西。

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