# Начало работы

Начнем с классического примера для большинства языков программирования - вывод строки "Hello world!". В нашем случае, её логирование.

```
package ru.log4j.Log4jHelloWorld;

import org.apache.log4j.Logger;

/**
 * Hello world!
 */
public class App {
    public static final Logger LOG=Logger.getLogger(App.class);
   public static void main(String[] args) {
       LOG.info("Hello World!");
   }
}
```

Настроим вывод log4j на экран:

```
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">

<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">

  <appender name="console" class="org.apache.log4j.ConsoleAppender">
    <param name="Target" value="System.out"/>
    <layout class="org.apache.log4j.PatternLayout">
      <param name="ConversionPattern" value="%p %c: %m%n"/>
   </layout>
 </appender>
 <!--Корневой logger-->
 <root>
   <priority value ="debug" />
   <appender-ref ref="console" />
 </root>
```

\</log4j:configuration>

Вопрос 1

```
Зачем используются системы логирования в программах?
```


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