如何正确打印枚举器元素？

Question

我想理解别人写的java程序，我不知道java。我写了一个简短的方法来转储请求对象的属性。

public void dumpRequest(HttpServletRequest request) {

    String[] attrNames = new String[100]; // hard coded

    int ani = 0;

    Enumeration rns = request.getAttributeNames();

    while (rns.hasMoreElements()) {

        out.println("attribute name: " + rns.nextElement());

        attrNames[ani] = rns.nextElement().toString();

        ani = ani + 1;

    }

    out.println("" + ani + " atributes");

    String cn;

    for (int n = 0; n < ani; n++) {

        cn = attrNames[n];

        out.println("** " + cn + " - " + request.getAttribute(cn));

    }

    out.println("++++++++++++++++++++++");

}

令我震惊的是，我意识到与我的代码输出相比，NetBeans 变量选项卡在请求对象上显示的属性多两倍。枚举似乎记录在这里：https : //tomcat.apache.org/tomcat-4.1-doc/catalina/docs/api/org/apache/catalina/util/Enumerator.html

我究竟做错了什么？

Answer 1

在此块中调用 nextElement 方法两次：while (rns.hasMoreElements()) {&nbsp; &nbsp; &nbsp; &nbsp; out.println("attribute name: " + rns.nextElement());&nbsp; &nbsp; &nbsp; &nbsp; attrNames[ani] = rns.nextElement().toString();&nbsp; &nbsp; &nbsp; &nbsp; ani = ani + 1;&nbsp; &nbsp; }你应该调用 nextElement 一次。把它放在变量中，然后使用该变量。