小编Seb*_*ebi的帖子

我目前正在使用ctime库中的时间.还有更快的选择吗？

time_t start_time, elapsed_time;

for(int i = 0; i < n; i++) {
    start_time = time(NULL);
    /// optimized code
    if(condition_met())
    {
       elapsed_time = time(NULL) - start_time;
    } else continue;
}

时间(NULL)只是不够快.

我正在使用向量,在某些时候会有NULL条目; 我想擦除给定向量中的所有NULL出现.到目前为止我的方法不起作用:

for(int i = sent_flit_list->size() - 1; i >= 0; i--)
if(sent_flit_list[i] == NULL)
    sent_flit_list->erase(sent_flit_list[i]);

for(int i = sent_pkt_list->size() - 1; i >= 0; i--)
if(sent_pkt_list[i] == NULL)
    sent_pkt_list->erase(sent_pkt_list[i]);

哪里

vector<Flit*> *sent_flit_list;
vector<Packet*> *sent_pkt_list;

是向量.我已经尝试转换为类型(Flit*)NULL /(Flit*)0但没有成功.

任何帮助将不胜感激.

我想了解/设想一个3D游戏引擎.您会推荐哪些书籍/参考/教程？我希望他们是关于C++/DirectX而不是Java.

我正在尝试使用java检索使用SSL证书的论坛的索引页面:

WebClient webClient = new WebClient(...);
HtmlPage sectionPage = webClient.getPage("https://rstforums.com/");

我已禁用SNI推荐这里编程调用任何SSL相关的方法之前.在第二次回答这个问题,并从第三这一个我加入了论坛的证书,证书列表:

C:\Program Files\Java\jdk1.8.0_65\jre\lib\security>keytool -import -alias RST_CERT -file forums_certificate -keystore cacerts

其中forums_certificate包括:

-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

证书已成功添加,并在列出其条目时显示在密钥库中:

rst_cert, Feb 3, 2016, trustedCertEntry, 
Certificate fingerprint (SHA1): 25:39:98:FC:FF:DE:2D:24:BC:F0:78:93:D6:2E:5A:55:64:D5:09:8A

当我尝试重新运行应用程序发出新请求时,会给出相同的错误:

sun.security.validator.ValidatorException: PKIX path building failed: sun.securi
ty.provider.certpath.SunCertPathBuilderException: unable to find valid certifica
tion path to requested …

我正在尝试将一组全局变量和函数从一个Javascript文件导出到nodejs中的另一个.

来自 node-js.include.js

var GLOBAL_VARIABLE = 10;

exports.GLOBAL_VARIABLE = GLOBAL_VARIABLE;

module.exports = {

    add: function(a, b) {
        return a + b;
    }

};

进入test-node-js-include.js:

var includes = require('./node-js-include');

process.stdout.write("We have imported a global variable with value " + includes.GLOBAL_VARIABLE);

process.stdout.write("\n and added a constant value to it " + includes.add(includes.GLOBAL_VARIABLE, 10));

但变量; 我得到以下输出:

We have imported a global variable with value undefined
 and added a constant value to it NaN

为什么不出口GLOBAL_VARIABLE？

我在使用远程 EJB 对象时遇到问题。JNDI 查找成功，但转换为对象并随后使用失败。EJB接口和实现如下：

UserViewBeanRemote.java

package books.pointejb;

import java.util.List;

import javax.ejb.Remote;

import books.pointejb.User;
import books.pointejb.Book;

@Remote
public interface UserViewBeanRemote {
    public boolean register(User user);
    // A user can delete his/her account, note that two users with the same username cannot exist
    public void delete(User user);
    public boolean login(User user);
    public boolean logout(User user);
    // Search only by book titles
    public List<Book> search(String title);
}

用户视图Bean.java

package books.pointejb;


import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import javax.ejb.Stateful;
import javax.management.Query;
import javax.persistence.EntityManager;  
import …

我编写了一个包装器类，以对类型向量执行插入/删除操作。代码：

class GenericSymbolTable {
   public:
       virtual void pushBackAtom(Atom *atom) = 0;
       virtual Atom* peekAtom(void) = 0;
       virtual Atom* getAtom(void) = 0;

   protected:
      ~GenericSymbolTable(void){}
};

class SymbolTable : public GenericSymbolTable {
   private:
       vector<Atom*> atoms;

   protected:
       ~SymbolTable(void);

   public:
       void pushBackAtom(Atom *atom);
       Atom* peekAtom(void);
       Atom* getAtom(void);
};

在为这些方法编写实现时，编译器会引发冲突的类型错误：

   Atom* SymbolTable::peekAtom(void) {
      if(atoms.empty()) {
          cout << "\t[W] Simbol table does not contain any atoms" << endl;
          return NULL;
      }

      Atom* first = atoms.begin(); // <== type error
      return first;
   }

   Atom* SymbolTable::getAtom(void) {
      if(atoms.empty()) …

我正在为注册表单编写验证servlet.表单位于.jsp文件中,并具有以下布局:

        <div class="content">
            <h2 class="form">Register</h2>
            <form action="Register">
                <p>
                    User name: <br />
                    <input type="text" name="username" /><br /> First Name: <br />
                    <input type="text" name="fist_name" /><br /> Last Name: <br />
                    <input type="text" name="last_name" /><br /> Email Address: <br />
                    <input type="text" name="email" /><br /> Password: <br />
                    <input type="password" name="password" /><br /> Retype password:
                    <br />
                    <input type="password" name="password2" /><br /> <input
                        type="submit" value="Register" />
                </p>
            </form>

            <!-- end .content -->
        </div>

验证代码应检查每个字段是否满足一组约束,如果不满足,则写回jsp错误消息.

ValidationServlet.java

protected void doPost(HttpServletRequest request,
            HttpServletResponse response) …

读完这个问题后,我设法运行了一个.jar文件,该文件在jar文件中有外部依赖项:

/usr/lib/jvm/java-8-jdk/bin/java -classpath /usr/local/bin/kiaragen.jar:/home/kiara/AppLab/KIARA/kiaragen/src/main/resources/org/fiware/kiara/generator/idl/templates/*:/usr/lib/jvm/java-8-jdk/jre/lib/*:/home/kiara/AppLab/KIARA/kiaragen/lib/*  org.fiware.kiara.generator.kiaragen

其中/usr/local/bin/kiaragen.jar是要执行的文件.现在,我正在尝试运行依赖于.class文件的不同版本:

/home/kiara/AppLab/KIARA/IDL-Parser/target/classes/com/eprosima/idl/parser/exception/ParseException.class

将文件添加到类路径:

/usr/lib/jvm/java-8-jdk/bin/java -classpath /usr/local/bin/kiaragen-0.2.0.jar:/home/kiara/AppLab/KIARA/IDL-Parser/target/classes/com/eprosima/idl/parser/exception/ParseException.class:/home/kiara/AppLab/KIARA/kiaragen/src/main/resources/org/fiware/kiara/generator/idl/templates/*:/usr/lib/jvm/java-8-jdk/jre/lib/*:/home/kiara/AppLab/KIARA/kiaragen/lib/*  org.fiware.kiara.generator.kiaragen

给出以下例外:

Error: A JNI error has occurred, please check your installation and try again
Exception in thread "main" java.lang.NoClassDefFoundError: com/eprosima/idl/parser/exception/ParseException
    at java.lang.Class.getDeclaredMethods0(Native Method)
    at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
    at java.lang.Class.privateGetMethodRecursive(Class.java:3048)
    at java.lang.Class.getMethod0(Class.java:3018)
    at java.lang.Class.getMethod(Class.java:1784)
    at sun.launcher.LauncherHelper.validateMainClass(LauncherHelper.java:544)
    at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:526)
Caused by: java.lang.ClassNotFoundException: com.eprosima.idl.parser.exception.ParseException
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 7 more

为什么？

.jar的清单文件与以前相同:

$ cat META-INF/MANIFEST.MF 
Manifest-Version: 1.0
Main-Class: org.fiware.kiara.generator.kiaragen

如何将.class文件添加到类路径？

如何将函数的输入参数的子集保留为python中的默认值？

例如,

>>> def sum(a=2, b=3):
...   print a + b

>>> sum(1,2)
3

>>> sum(1)
4

我怎么能离开一个为2,仅改变b的值？就像是:

sum(_,4) # a is 2 and b 4, and sum should print 6

我有一个结构:

struct ListNode {
     int val;
     ListNode *next;
     ListNode(int x) : val(x), next(NULL) {}
};

我正在尝试初始化它:

ListNode* res = new ListNode();
ListNode* start = res;

但我得到:

error C2512: 'ListNode' : no appropriate default constructor available

为什么？