在Java中利用JavaScript引擎解析并计算数学表达式字符串

implementation 'io.apisense:rhino-android:1.1.1'
// 或者对于非Android项目，可以使用 org.mozilla:rhino
// implementation 'org.mozilla:rhino:1.7.7.2'

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import android.util.Log; // 假设在Android环境，非Android项目可替换为System.out.println

public class MathExpressionEvaluator {

    public static double evaluateMathExpression(String expression) {
        Object result = null;
        // 获取脚本引擎管理器
        ScriptEngineManager manager = new ScriptEngineManager();
        // 通过名称获取Rhino JavaScript引擎
        ScriptEngine engine = manager.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
            throw new UnsupportedOperationException("JavaScript scripting engine (Rhino) not found. " +
                                                    "Please ensure the Rhino dependency is correctly added.");
        }

        try {
            // 评估字符串表达式
            // 例如："5+5" 将返回 10
            // "10/2" 将返回 5
            // "3 * (4 + 2) - 1" 将返回 17
            result = engine.eval(expression);
        } catch (ScriptException e) {
            // 捕获脚本执行异常，例如表达式语法错误
            Log.e("MathExpressionEvaluator", "Error evaluating expression: " + expression, e);
            throw new IllegalArgumentException("Invalid mathematical expression: " + expression, e);
        } catch (Exception e) {
            // 捕获其他可能的异常
            Log.e("MathExpressionEvaluator", "An unexpected error occurred during evaluation: " + expression, e);
            throw new RuntimeException("Failed to evaluate expression: " + expression, e);
        }

        if (result == null) {
            throw new IllegalStateException("Evaluation returned null for expression: " + expression);
        }

        // 将评估结果转换为double类型
        // Rhino通常返回Double或Integer，toString()可以统一处理
        try {
            return Double.parseDouble(result.toString());
        } catch (NumberFormatException e) {
            Log.e("MathExpressionEvaluator", "Could not convert result to double: " + result.toString(), e);
            throw new IllegalStateException("Failed to convert evaluation result to number: " + result.toString(), e);
        }
    }

    public static void main(String[] args) {
        // 示例用法
        try {
            double value1 = evaluateMathExpression("5+5");
            System.out.println("Result for '5+5': " + value1); // 输出 10.0

            double value2 = evaluateMathExpression("10/2");
            System.out.println("Result for '10/2': " + value2); // 输出 5.0

            double value3 = evaluateMathExpression("3 * (4 + 2) - 1");
            System.out.println("Result for '3 * (4 + 2) - 1': " + value3); // 输出 17.0

            double value4 = evaluateMathExpression("Math.pow(2, 3) + 1"); // JavaScript的Math对象
            System.out.println("Result for 'Math.pow(2, 3) + 1': " + value4); // 输出 9.0

            // 尝试一个无效表达式
            // double invalidValue = evaluateMathExpression("5 + * 2"); // 将抛出IllegalArgumentException
            // System.out.println("Result for '5 + * 2': " + invalidValue);

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