学步园

昨天，看到一求助表达式计算的帖子，才知道，原来java里有封装了这样的类。

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

/*
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 * and open the template in the editor.
 */

/**
 *
 * @author Administrator
 */
public class expression {
    public static void main(String []args) throws IOException, ScriptException
    {
        String str=new String();
        BufferedReader in= new BufferedReader(new InputStreamReader(System.in));
        while(true==true)
        {
            System.out.println("请输入要计算的表达式:");
            str=in.readLine();
            if(str.equals("end"))
                break;
            ScriptEngineManager manager = new ScriptEngineManager();
            ScriptEngine engine = manager.getEngineByName("js");
            Object result = engine.eval(str);
        
        System.out.println("结果类型:" + result.getClass().getName() + ",计算结果:" + result);
        }
    }
}