Java中利用Rhino引擎评估含数学符号的字符串表达式

dependencies {
    implementation 'io.apisense:rhino-android:1.1.1'
}

dependencies {
    implementation 'org.mozilla:rhino:1.7.7.2' // 或更高版本
}

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import android.util.Log; // 适用于Android项目

public class ExpressionEvaluator {

    private static final String TAG = "ExpressionEvaluator";

    public static double evaluateMathExpression(String expression) {
        Object result = null;
        // 获取Rhino JavaScript引擎实例
        ScriptEngine engine = new ScriptEngineManager().getEngineByName("rhino");

        if (engine == null) {
            // 如果Rhino引擎未找到，抛出异常或进行其他错误处理
            Log.e(TAG, "JavaScript scripting engine (Rhino) not found.");
            throw new UnsupportedOperationException("JavaScript scripting engine (Rhino) not found.");
        }

        try {
            // 使用eval方法评估字符串表达式
            result = engine.eval(expression);
            Log.i(TAG, "Expression: " + expression + ", Result (Object): " + result);

            // 将评估结果转换为double类型
            if (result instanceof Number) {
                return ((Number) result).doubleValue();
            } else if (result != null) {
                // 如果结果不是Number类型，尝试将其字符串化后解析
                return Double.parseDouble(result.toString());
            } else {
                Log.e(TAG, "Evaluation returned null for expression: " + expression);
                throw new IllegalArgumentException("Expression evaluation returned null.");
            }

        } catch (ScriptException e) {
            // 捕获脚本执行异常，例如表达式语法错误
            Log.e(TAG, "Error evaluating script: " + expression, e);
            throw new IllegalArgumentException("Invalid mathematical expression: " + expression, e);
        } catch (NumberFormatException e) {
            // 捕获将结果转换为double时的异常
            Log.e(TAG, "Error converting result to double for expression: " + expression, e);
            throw new IllegalArgumentException("Could not convert evaluation result to double.", e);
        } catch (Exception e) {
            // 捕获其他未知异常
            Log.e(TAG, "An unexpected error occurred during evaluation: " + expression, e);
            throw new RuntimeException("An unexpected error occurred.", e);
        }
    }

    public static void main(String[] args) {
        // 示例用法 (在Android项目中，这些Log会输出到Logcat)
        try {
            double val1 = evaluateMathExpression("5+5");
            System.out.println("Result of '5+5': " + val1); // 预期输出 10.0

            double val2 = evaluateMathExpression("10 / 3.0");
            System.out.println("Result of '10 / 3.0': " + val2); // 预期输出 3.333...

            double val3 = evaluateMathExpression("(2 + 3) * 4 - 1");
            System.out.println("Result of '(2 + 3) * 4 - 1': " + val3); // 预期输出 19.0

            // 尝试一个无效的表达式
            // double val4 = evaluateMathExpression("5 + * 3"); // 会抛出异常
            // System.out.println("Result of '5 + * 3': " + val4);

        } catch (Exception e) {
            System.err.println("Evaluation failed: " + e.getMessage());
        }
    }
}