java 将字符串转成算术表达式进行计算

转自 http://blog.csdn.net/linminqin/article/details/41804955

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

public class ExpressTest {  

    public static void test1() throws ScriptException {  
        String str = "(a >= 0 && a <= 5)";  
        ScriptEngineManager manager = new ScriptEngineManager();  
        ScriptEngine engine = manager.getEngineByName("js");  
        engine.put("a", 4);  
        Object result = engine.eval(str);  
        System.out.println("结果类型:" + result.getClass().getName() + ",计算结果:" + result);  
    }  

    public static void test2() throws ScriptException {  
        String str = "43*(2 + 1.4)+2*32/(3-2.1)";  
        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);  
    }  

    public static void main(String[] args) throws ScriptException {  
        test1();  
        test2();  
    }  
}