java执行字符串公式的三种方法总结

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

public class EvaluateExpression {
    public static void main(String[] args) {
        // 示例公式字符串(从数据库中获取)
        String expression = "3 + 5 * (2 - 8)";

        // 创建一个脚本引擎管理器
        ScriptEngineManager manager = new ScriptEngineManager();
        // 获取一个JavaScript引擎
        ScriptEngine engine = manager.getEngineByName("JavaScript");

        try {
            // 执行公式并获取结果
            Object result = engine.eval(expression);
            // 将结果转换为字符串并打印
            System.out.println("公式" + expression + "的执行结果是："+ result);
        } catch (ScriptException e) {
            // 捕获并处理脚本异常
            System.err.println(e.getMessage());
        }
    }
}

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

public class EvaluateExpression {
    public static void main(String[] args) {
        // 示例公式字符串(从数据库中获取)
        String expression = "3 + a * (2 - b) + a";

        // 创建一个脚本引擎管理器
        ScriptEngineManager manager = new ScriptEngineManager();
        // 获取一个JavaScript引擎
        ScriptEngine engine = manager.getEngineByName("JavaScript");
        String a = "5", b = "8";
        try {
            // 执行公式并获取结果
            Object result = engine.eval(expression.replaceAll("a", a).replace("b", b));
            // 将结果转换为字符串并打印
            System.out.println("公式" + expression + "的执行结果是："+ result);
        } catch (ScriptException e) {
            // 捕获并处理脚本异常
            System.err.println(e.getMessage());
        }
    }
}

<dependency>
    <groupId>net.objecthunter</groupId>
    <artifactId>exp4j</artifactId>
    <version>0.4.8</version>
</dependency>

import net.objecthunter.exp4j.Expression;
   import net.objecthunter.exp4j.ExpressionBuilder;
   
   public class FormulaCalculator {
       public static void main(String[] args) {
           String formula = "10 * (3 + 2) / 5";
           Expression expression = new ExpressionBuilder(formula).build();
           double result = expression.evaluate();
           System.out.println(result);  // 输出: 10.0
       }
   }

import org.springframework.expression.Expression;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.spel.standard.SpelExpressionParser;

public class FormulaCalculator {
    public static void main(String[] args) {
        String formula = "10 * (3 + 2) / 5";
        ExpressionParser parser = new SpelExpressionParser();
        Expression exp = parser.parseExpression(formula);
        Integer result = exp.getValue(Integer.class);
        System.out.println(result);  // 输出: 10
    }
}