我在启动JBOSS 7 AS服务器时遇到错误,如下所示......
JBoss引导环境
JBOSS_HOME:C:\ EAP-6.0.0.GA\jboss-eap-6.0
JAVA:C:\ Program Files\Java\jdk1.7.0\bin\java
JAVA_OPTS:-client -Dprogram.name = standalone.bat -Xms1303M -Xmx1303M -XX:MaxPermSize = 256M
VM初始化期间发生错误
Could not reserve enough space for object heap
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.
Press any key to continue . . .
我经常使用两种形式:java中的short和long(也是减法,乘法等)运算符.而且我认为这不会影响性能或速度,但我对这些问题感到困惑:"为什么java创建者提供了这种运算符的两种形式？它们之间有什么区别？" 那么,两种形式之间的真正区别是什么:
int a = 10, b = 3;
b = b + a;
和
int a = 10, b = 3;
b += a;
有人可以解释一下吗？可能两种形式之间的差异隐藏在较低的水平？每本书都只说:"Java也有复合算子......"但没有关于差异的说法.
我是Spring Security的新手.我试图用标准搜索,is:question [spring-security] error message when user does not exist但没有帖子帮助.
目前,我用于Spring Security 3.1在我的Web应用程序中验证用户身份.我的实现如下:
DaoAuthenticationProvider如AuthenticationProviderUserDetailsService使用的实现DaoAuthenticationProvider这是userDetailsServiceImpl豆子:
@Service("userDetailsServiceImpl")
@Transactional(readOnly = true, propagation = Propagation.REQUIRED)
public class UserDetailsServiceImpl implements UserDetailsService {
@Autowired
private UserDao userDao;
@Override
public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
User existingUser = this.userDao.getUserByUsername(username);
// TODO create a schema for storing ROLEs in database
List<GrantedAuthority> roles = new ArrayList<GrantedAuthority>();
roles.add(Role.USER);
org.springframework.security.core.userdetails.User user = new org.springframework.security.core.userdetails.User(
existingUser.getUsername(), existingUser.getPassword(), …我需要在应用程序中实现集群机制。这样做时启动jbossAS7时出现错误，错误是：
=========================================================================
JBoss Bootstrap Environment
JBOSS_HOME: /home/chandrashekar/CHE/SoftWares/jboss-as-7.1.1.Final
JAVA: java
JAVA_OPTS: -Xms64m -Xmx512m -XX:MaxPermSize=256m -Djava.net.preferIPv4Stack=true -Dorg.jboss.resolver.warning=true -Dsun.rmi.dgc.client.gcInterval=3600000 -Dsun.rmi.dgc.server.gcInterval=3600000 -Djboss.modules.system.pkgs=org.jboss.byteman -Djava.awt.headless=true -Djboss.domain.default.config=domain.xml -Djboss.host.default.config=host.xml
=========================================================================
19:18:52,599 INFO [org.jboss.modules] (main) JBoss Modules version 1.1.1.GA
19:18:52,688 INFO [org.jboss.as.process.Host Controller.status] (main) JBAS012017: Starting process 'Host Controller'
[Host Controller] 19:18:53,082 INFO [org.jboss.modules] (main) JBoss Modules version 1.1.1.GA
[Host Controller] 19:18:53,196 INFO [org.jboss.msc] (main) JBoss MSC version 1.0.2.GA
[Host Controller] 19:18:53,251 INFO [org.jboss.as] (MSC service thread 1-3) JBAS015899: JBoss AS 7.1.1.Final "Brontes" starting
[Host Controller] 19:18:54,070 ERROR [org.jboss.as.controller.management-operation] …我正在制作一个ATM程序,用cmd来学习java来编译和运行它.该程序编译时没有错误,但在运行时只打印at ATM.(init)(ATM.java:6).
任何帮助将不胜感激!
public class ATM
{
Toolbox myToolbox = new Toolbox();
Integer balance;
ATM myATM = new ATM();
public static void main(String[] arg)
{
ATM myATM = new ATM();
myATM.go();
myATM.printBal();
myATM.mainMenu();
}
public void go()
{
System.out.println("Welcome to online ATM banking");
System.out.println("How much do you want in your account?");
//System.out.println("Enter your number");
balance = myToolbox.readIntegerFromCmd();
}
public void printBal()
{
System.out.println("****************************************");
System.out.println(balance);
System.out.println("****************************************");
}
public void mainMenu()
{
Integer selected;
System.out.println("What do you want to do?"); …public class num {
public static void main(String args[]) {
int i = 5, j = 9, k = 3;
int w, x;
w = i | j | k;
x = i &j & k;
System.out.println(w);
System.out.println(x);
}
}
为什么价值观w = 15和x = 1？
我知道当一个类有一个内部类时,这个类将被编译为两个类文件.今天我的代码如下
public class GenericDeserializer {
public static void main(String[] args) {
String cityPageLoadJson = "{\"count\":2,\"pageLoad\":[{\"id\":4,\"name\":\"HAN\"},{\"id\":8,\"name\":\"SGN\"}]}";
Type type = new TypeToken<GenericResult<City>>() {
}.getType();
Gson gson = new GsonBuilder().setPrettyPrinting().create();
GenericResult<City> cityPageLoad = gson.fromJson(cityPageLoadJson, type);
for (City city : cityPageLoad.getPageLoad()) {
System.out.println(gson.toJson(city));
}
}
}
虽然上面没有内部类,但java编译器仍会创建两个类文件:
GenericDeserializer.class
GenericDeserializer$1.class
使用Java Decompiler工具,我看到第二个内容
package net.tuandn.training.lesson.gson;
import com.google.gson.reflect.TypeToken;
import net.tuandn.training.model.City;
import net.tuandn.training.model.GenericResult;
final class GenericDeserializer$1 extends TypeToken<GenericResult<City>>
{
}
请问有谁可以解释为什么要创建这个类？
什么时候编译多个类文件？
非常感谢!
我定义了一个对象并声明了一个静态变量i.在该get()方法中,当我尝试打印实例和类变量时,两者都打印相同的值.
不是this.i实例变量吗？它应该打印0而不是50吗？
public class test {
static int i = 50;
void get(){
System.out.println("Value of i = " + this.i);
System.out.println("Value of static i = " + test.i);
}
public static void main(String[] args){
new test().get();
}
}