是不一样的,对于A && B 这样的布尔表达式,先计算A,若A为false,则不会计算B,其实可以用下面的语句来表达这种'短路':
A && B <=> if(A)
{
if(B) return true;
else return false;
}
else return false;
据我所知,C++,java里面都是这种语意,
A && B <=> if(A)
{
if(B) return true;
else return false;
}
else return false;
据我所知,C++,java里面都是这种语意,
还是不行啊,问题是在生成第二个表单再提交时,抱错:
java.lang.NullPointerException
at /jsp/Myjsp/Firstjsp.jsp._jspService(/jsp/Myjsp/Firstjsp.jsp.java:35) (JSP page line 14)
at com.orionserver[Orion/1.5.3 (build 10509)].http.OrionHttpJspPage.service(.:56)
at com.evermind[Orion/1.5.3 (build 10509)]._co._skc(.:5510)
at com.evermind[Orion/1.5.3 (build 10509)].server.http.JSPServlet.service(.:31)
at com.evermind[Orion/1.5.3 (build 10509)]._bxb._crd(.:501)
at com.evermind[Orion/1.5.3 (build 10509)]._bxb._ukb(.:170)
at com.evermind[Orion/1.5.3 (build 10509)]._cn._uab(.:576)
at com.evermind[Orion/1.5.3 (build 10509)]._cn._fm(.:189)
at com.evermind[Orion/1.5.3 (build 10509)]._bs.run(.:62)
{
//key is null or key==""
}
else {
out.print("<font color='red'>hello</font>");
}
记得java里面是从前向后,从左到右执行的,对于或操作,前一个条件满足了的话,第二个条件是不执行的。