判断一个表达式是否正确

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


public class Test {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		        ScriptEngineManager manager = new ScriptEngineManager();
		 
		        ScriptEngine engine = manager.getEngineByName("javascript");
		        try {
		        	String s1="10*5+9-25/2";
		            Double d = (Double) engine.eval(s1);
		            //if()
		            System.out.println(d);
		        } catch (ScriptException ex) {
		        	System.out.println("表达式错误!");
		        }
		 
		    }
	}