java中使用javascript实现计算器功能

不废话,直接上代码:

package org.galo.thread;

import java.util.Scanner;

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

public class Calculator {
	
	private static final String WELCOME_MESSAGE = "请输入计算表达式：(或'exit'退出)";
	private static final String EXIT_MESSAGE = "系统正在退出,请稍后";
	private static final String QUIT_MESSAGE = "感谢您的使用,再见!";
	private static final String ERROR_MESSAGE = "[表达式语法错误]请输入：(或'exit'退出)";
	
	public static void main(String[] args) {
		
		
		sayWelcome();
		main();
	}

	public static void main() {
		Scanner scanner = new Scanner(System.in);
		println(WELCOME_MESSAGE);
		while(scanner.hasNext()){
			
			String exp = scanner.next();
			long startTime = System.currentTimeMillis();
			if("exit".equals(exp)){
				
				doExit();
				return;
			}
			String result = evalJS(exp);
			if(result == null){
				
				continue;
			}
			long endTime = System.currentTimeMillis();
			println("计算结果：" + result + " ;用时：" + (endTime - startTime) + "ms");
			println("");
			println(WELCOME_MESSAGE);
		}
	}

	private static void doExit() {
		
		print(EXIT_MESSAGE);
		for (int i = 0; i < 6; i++) {
			
			try {
				Thread.sleep(500);
				print(".");
			} catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		println("");
		println(QUIT_MESSAGE);
	}

	public static void sayWelcome() {
		
		println("****************************");
		println("*******JAVA计算器V0.1********");
		println("**********欢迎使用************");
		println("****************************");
	}

	private static String evalJS(String exp) {
		
		Double result;
		ScriptEngineManager sem = new ScriptEngineManager();
		ScriptEngine se = sem.getEngineByName("javascript");
		String script = "function compute(){return " +
				exp +
				"};";
		try {
			se.eval(script);
			Invocable invocable = (Invocable) se;
			result = (Double) invocable.invokeFunction("compute", new Object[]{});
			return result.toString();
		} catch (ScriptException e) {
			
			println("");
			println(ERROR_MESSAGE);
			return null;
		} catch (NoSuchMethodException e) {

			println("");
			println(ERROR_MESSAGE);
			return null;
		}
	}
	
	public static void println(String word){
		
		System.out.println(word);
	}
	public static void print(String word){
		
		System.out.print(word);
	}
}

还有java中的javascript中调用java对象.感兴趣玩玩的,呵呵