Java中利用Rhino引擎评估字符串数学表达式并转换为数值类型

dependencies {
    // ... 其他依赖
    implementation 'io.apisense:rhino-android:1.1.1' 
}

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import android.util.Log; // 如果是Android项目，使用Log; 否则可替换为System.out.println

public class ExpressionEvaluator {

    private static final String TAG = "ExpressionEvaluator";

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

        // 检查引擎是否成功加载
        if (engine == null) {
            // 如果Rhino引擎未找到，尝试获取通用的JavaScript引擎
            engine = manager.getEngineByName("JavaScript");
            if (engine == null) {
                throw new UnsupportedOperationException("JavaScript scripting engine not found");
            }
            Log.w(TAG, "Rhino engine not found, falling back to generic JavaScript engine.");
        }

        try {
            // 使用eval()方法评估字符串表达式
            result = engine.eval(expression); 

            // 将结果转换为字符串，然后解析为double类型
            if (result != null) {
                String resultString = result.toString();
                double val = Double.parseDouble(resultString);
                Log.i(TAG, "Expression: " + expression + " -> Result: " + val);
                return val;
            } else {
                Log.e(TAG, "Evaluation returned null for expression: " + expression);
                return Double.NaN; // 或者抛出异常
            }
        } catch (ScriptException e) {
            // 捕获脚本执行异常，例如表达式语法错误
            Log.e(TAG, "Script evaluation error for expression: " + expression, e);
            throw new IllegalArgumentException("Invalid mathematical expression: " + expression, e);
        } catch (NumberFormatException e) {
            // 捕获数值转换异常
            Log.e(TAG, "Failed to parse evaluated result to double: " + result, e);
            throw new RuntimeException("Could not convert evaluated result to number: " + result, e);
        } catch (Exception e) {
            // 捕获其他未知异常
            Log.e(TAG, "An unexpected error occurred during evaluation for expression: " + expression, e);
            throw new RuntimeException("Unexpected error evaluating expression: " + expression, e);
        }
    }

    public static void main(String[] args) {
        // 示例用法
        try {
            double value1 = evaluateMathExpression("5+5"); // 结果应为 10.0
            System.out.println("5+5 = " + value1);

            double value2 = evaluateMathExpression("10 * (2 + 3) / 2.5"); // 结果应为 20.0
            System.out.println("10 * (2 + 3) / 2.5 = " + value2);

            double value3 = evaluateMathExpression("Math.pow(2, 3) + 1"); // 结果应为 9.0 (JavaScript的Math对象)
            System.out.println("Math.pow(2, 3) + 1 = " + value3);

            // 示例：错误表达式
            // double value4 = evaluateMathExpression("5+"); // 将抛出异常
            // System.out.println("5+ = " + value4);

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