Java解析变量公式的简单示例

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
public class FormulaParser {
    public static Object parseFormula(String formula) {
        ScriptEngineManager manager = new ScriptEngineManager();
        ScriptEngine engine = manager.getEngineByName("js");
        try {
            return engine.eval(formula);
        } catch (ScriptException e) {
            e.printStackTrace();
            return null;
        }
    }
    public static void main(String[] args) {
        String formula = "a + b * (c - d)";
        // 设置变量值
        double a = 10;
        double b = 5;
        double c = 20;
        double d = 3;
        Object result = parseFormula(formula);
        System.out.println("计算结果：" + result);
    }
}

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
public class OrderCalculator {
    public static double calculateTotalPrice(double unitPrice, int quantity, double discountRate) throws ScriptException {
        String formula = unitPrice + " * " + quantity + " * (1 - " + discountRate + ")";
        return (double) parseFormula(formula);
    }
    public static Object parseFormula(String formula) throws ScriptException {
        ScriptEngineManager manager = new ScriptEngineManager();
        ScriptEngine engine = manager.getEngineByName("js");
        return engine.eval(formula);
    }
    public static void main(String[] args) {
        double unitPrice = 100.0;
        int quantity = 5;
        double discountRate = 0.2;
        try {
            double totalPrice = calculateTotalPrice(unitPrice, quantity, discountRate);
            System.out.println("订单实际金额为: " + totalPrice);
        } catch (ScriptException e) {
            e.printStackTrace();
        }
    }
}