Java 中計算字符串表達式的值

Java 中計算字符串表達式的值

在 Java 中計算字符串數值表達式可以用 javax.script.ScriptEngine#eval(java.lang.String)，通過調用 JavaScript 來計算

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

public class ExpressionCalculate {
    public static void main(String[] args) {
        ScriptEngineManager scriptEngineManager = new ScriptEngineManager();
        ScriptEngine scriptEngine = scriptEngineManager.getEngineByName("nashorn");
        String expression = "10 * 2 + 6 / (3 - 1)";

        try {
            String result = String.valueOf(scriptEngine.eval(expression));
            System.out.println(result);
        } catch (ScriptException e) {
            e.printStackTrace();
        }
    }
}

結果： 23