Java自定义公式计算

代码

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class RegexTest {

    public static void main(String[] args) {
        Map<Integer, Double> map = new LinkedHashMap<>();
        map.put(0,1.0);
        map.put(1,1.0);
        String formulas = "([q1] + [q2]) / 2 ";
        double calculate = calculate(formulas, map);
        System.out.println("calculate:  " + calculate);
    }

	/**
	*计算方法
	*/
   public double calculate(String formulas, Map<Integer, Double> questionScore) {
        log.info("自定义分数计算，formulas={}，questionScore={}", formulas, questionScore);
        //即"\\[q\\d+]"。这个模式表示以"["开头，紧接着是字母"q"，然后是一个或多个数字，最后以"]"结尾的字符串。
        String regex = "\\[q\\d+]";
        Pattern compile = Pattern.compile(regex);
        //提取公式中的占位符 例：[q1]
        Matcher m = compile.matcher(formulas);
        //获取题号
        List<Integer> qSeq = new ArrayList<>();
        while (m.find()) {
            //提取标志位中的题号
            qSeq.add(Integer.valueOf(formulas.substring(m.start() + 2, m.end() - 1)));
        }

        String evalStr = null;
        for (int i = 0; i < qSeq.size(); i++) {
            Integer index = qSeq.get(i);
            if (i == 0) {
                //将题号 [q1]替换为对应的实际分数
                evalStr = formulas.replace("[q" + index + "]", String.valueOf(questionScore.get(index)));
            } else {
                evalStr = evalStr.replace("[q" + index + "]", String.valueOf(questionScore.get(index)));
            }
        }
        ScriptEngineManager manager = new ScriptEngineManager();
        ScriptEngine engine = manager.getEngineByName("js");
        Object result = 0;
        try {
            if (Objects.isNull(evalStr)) {
                throw new BizException("自定义公式不正确");
            }
            result = engine.eval(evalStr);
        } catch (ScriptException e) {
            log.info("转换分数异常");
        }
        BigDecimal two = BigDecimal.valueOf((Double) result);
        return two.setScale(2, RoundingMode.HALF_UP).doubleValue();
    }

结果