JDK之Enumeration

2024-03-28 04:18

文章标签 jdk enumeration

本文主要是介绍JDK之Enumeration，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

源码

package java.util;/*** @author  Lee Boynton* @since   JDK1.0*/
public interface Enumeration<E> {boolean hasMoreElements();E nextElement();
}

Enumeration的遍历

Spring之ContextCleanupListener源码

package org.springframework.web.context;import java.util.Enumeration;
import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;import org.springframework.beans.factory.DisposableBean;public class ContextCleanupListener implements ServletContextListener {private static final Log logger = LogFactory.getLog(ContextCleanupListener.class);@Overridepublic void contextInitialized(ServletContextEvent event) {}@Overridepublic void contextDestroyed(ServletContextEvent event) {cleanupAttributes(event.getServletContext());}static void cleanupAttributes(ServletContext sc) {Enumeration<String> attrNames = sc.getAttributeNames();// 测试此枚举是否包含更多的元素while (attrNames.hasMoreElements()) {// 如果此枚举对象至少还有一个可提供的元素，则返回此枚举的下一个元素。String attrName = attrNames.nextElement();if (attrName.startsWith("org.springframework.")) {Object attrValue = sc.getAttribute(attrName);if (attrValue instanceof DisposableBean) {try {((DisposableBean) attrValue).destroy();}catch (Throwable ex) {logger.error("Couldn't invoke destroy method of attribute with name '" + attrName + "'", ex);}}}}}}

相关源码

org.apache.catalina.core.ApplicationContext.getAttributeNames()方法

@Override
public Enumeration<String> getAttributeNames() {Set<String> names = new HashSet<>();names.addAll(attributes.keySet());return Collections.enumeration(names);
}

java.util.Collections.enumeration(Collection)方法

public static <T> Enumeration<T> enumeration(final Collection<T> c) {return new Enumeration<T>() {private final Iterator<T> i = c.iterator();public boolean hasMoreElements() {return i.hasNext();}public T nextElement() {return i.next();}};
}