Java String to complete mathematical sum

Question

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 a

Answer 1

You can use the JavaScript engine:

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

Edit to allow all equations:

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));

So then you can do something like:

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

Anything you want.