java - 如何将字符串 "7/7"转换为 Int 1？

Question

这个问题已经有答案了:

How to evaluate a math expression given in string form? (27 个回答)

已关闭 3 年前。

我正在尝试用 Java 制作一个计算器 GUI，但是我不知道如何将“7/7”转换为 double 。

我尝试过将其直接转换为 double ，但无法使其工作。

private class handler implements ActionListener{

    String answerString = "";
    int answerDouble;

    public void actionPerformed(ActionEvent e) {

        if(e.getSource() == clear) {
            answerString = "";
            result.setText(answerString);
        }
        if(e.getSource() == openBracket) {
            answerString = answerString + "(";
            result.setText(answerString);
        }
        if(e.getSource() == closeBracket) {
            answerString = answerString + ")";
            result.setText(answerString);
        }
        if(e.getSource() == divide) {
            answerString = answerString + "/";
            result.setText(answerString);
        }
        if(e.getSource() == seven) {
            answerString = answerString + "7";
            result.setText(answerString);
        }
        if(e.getSource() == equal) {
            answerDouble = Integer.parseInt(answerString);
            answerString = Double.toString(answerDouble);
            result.setText(answerString);
        }
    }

}

它应该显示 1 表示 7/7，但在命令行上输出错误。

Answer 1

您可以使用 JavaScript ScriptEngine 来计算此类表达式:

String expression = "7/7";
ScriptEngine scriptEngine = new ScriptEngineManager().getEngineByName("JavaScript");
System.out.println(scriptEngine.eval(expression)); // you will have to handle ScriptException

输出:

1