Java程序将数学字符串转换为int
若要将数学字符串计算为int，请使用Java中的NashornJavaScript（即脚本）。Nashorn调用Java7中引入的动态功能以提高性能。
要编写脚本，请对引擎使用ScriptEngineManager类：
ScriptEngineManager scriptEngineManager = new ScriptEngineManager();
ScriptEngine scriptEngine = scriptEngineManager.getEngineByName("nashorn");现在，用于put()在ScriptEngine的状态下设置键/值对：
scriptEngine.put("one", 10);
scriptEngine.put("two", 50);
scriptEngine.put("three", 40);现在，这是数学字符串。使用eval评估：
String strExp = "(one + two - three) == 20"; Object evalExp = scriptEngine.eval(strExp);
示例
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
public class Demo {
public static void main(String[] args) {
ScriptEngineManager scriptEngineManager = new ScriptEngineManager();
ScriptEngine scriptEngine = scriptEngineManager.getEngineByName("nashorn");
scriptEngine.put("one", 10);
scriptEngine.put("two", 50);
scriptEngine.put("three", 40);
try {
String strExp = "(one + two - three) == 20";
Object evalExp = scriptEngine.eval(strExp);
System.out.println("Is "+strExp + " ? " + evalExp);
} catch (ScriptException se) {
se.printStackTrace();
}
}
}输出结果
Is (one + two - three) == 20 ? true