Java-如何使用文本文件中声明的变量

我想使用文件中声明的变量，因为它是函数变量（接口）。 对于函数的每个声明（每行一个），我想将其添加到函数表中。可能吗？是否有一个函数来检索代码中声明的变量

谢谢

TestFunction.java

    ArrayList<Function> functions = new ArrayList<Function>();=

    Path file = Paths.get("./FunctionsDeclarations");
    try (InputStream in = Files.newInputStream(file);
        BufferedReader reader =
          new BufferedReader(new InputStreamReader(in))) {
        String line = null;
        while ((line = reader.readLine()) != null) {
            System.out.println(line);
    //Ex: line = "Function f = times(X, compose(SIN, times(constant(2.), X)));"
    //I want to use the Function variable f after the reading file : functions.add(f);
            new ScriptEngineManager().getEngineByName("js").eval(line);
        }
    } catch (IOException x) {
        System.err.println(x);
    }

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您可以使用

ScriptEngine

实例求值函数并在以后调用：

    ScriptEngineManager engineManager = new ScriptEngineManager();
    ScriptEngine engine = engineManager.getEngineByName("js");

    engine.eval("f = function() { return 1; }");

    Invocable invocable = (Invocable) engine;
    System.out.println(invocable.invokeFunction("f"));

本例中打印了1.0

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如果您需要评估Java表达式，请查看JEXL:

请提出明确的问题，并为给定的输入提供预期的输出。@user3185672我仍然不清楚。查看您的问题标题和问题，令人困惑

    ScriptEngineManager engineManager = new ScriptEngineManager();
    ScriptEngine engine = engineManager.getEngineByName("js");

    engine.eval("f = function() { return 1; }");

    Invocable invocable = (Invocable) engine;
    System.out.println(invocable.invokeFunction("f"));