StandardWatchEventKinds.java

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package java.nio.file;

/**
 * Defines the <em>standard</em> event kinds.
 *
 * @since 1.7
 */
// 被监视事件类型的标准实现
public final class StandardWatchEventKinds {
    
    /**
     * A special event to indicate that events may have been lost or discarded.
     *
     * The {@link WatchEvent#context context} for this event is implementation specific and may be {@code null}.
     * The event {@link WatchEvent#count count} may be greater than {@code 1}.
     *
     * @see WatchService
     */
    /*
     * 一个特殊事件，指示事件可能已丢失或丢弃；
     *
     * 当工作线程(服务线程)准备向主线程反馈该类型的事件时，往往会忽略该事件之后反馈的一系列事件，直到该事件本身被处理。
     */
    public static final WatchEvent.Kind<Object> OVERFLOW = new StdWatchEventKind<>("OVERFLOW", Object.class);
    
    /**
     * Directory entry created.
     *
     * When a directory is registered for this event then the {@link WatchKey} is queued
     * when it is observed that an entry is created in the directory or renamed into the directory.
     * The event {@link WatchEvent#count count} for this event is always {@code 1}.
     */
    // 被监听目录中发生了新建/重命名事件，事件计数为1
    public static final WatchEvent.Kind<Path> ENTRY_CREATE = new StdWatchEventKind<>("ENTRY_CREATE", Path.class);
    
    /**
     * Directory entry deleted.
     *
     * When a directory is registered for this event then the {@link WatchKey} is queued
     * when it is observed that an entry is deleted or renamed out of the directory.
     * The event {@link WatchEvent#count count} for this event is always {@code 1}.
     */
    // 被监听目录中发生了移除/重命名事件，事件计数为1
    public static final WatchEvent.Kind<Path> ENTRY_DELETE = new StdWatchEventKind<>("ENTRY_DELETE", Path.class);
    
    /**
     * Directory entry modified.
     *
     * When a directory is registered for this event then the {@link WatchKey} is queued
     * when it is observed that an entry in the directory has been modified.
     * The event {@link WatchEvent#count count} for this event is {@code 1} or greater.
     */
    // 被监听目录中发生了更改事件，事件计数可能大于1
    public static final WatchEvent.Kind<Path> ENTRY_MODIFY = new StdWatchEventKind<>("ENTRY_MODIFY", Path.class);
    
    
    private StandardWatchEventKinds() {
    }
    
    
    // 被监视事件类型的标准实现，通常包括创建/移除/更改事件
    private static class StdWatchEventKind<T> implements WatchEvent.Kind<T> {
        private final String name;      // 被监视事件名称
        private final Class<T> type;    // 被监视事件的上下文类型
        
        StdWatchEventKind(String name, Class<T> type) {
            this.name = name;
            this.type = type;
        }
        
        @Override
        public String name() {
            return name;
        }
        
        @Override
        public Class<T> type() {
            return type;
        }
        
        @Override
        public String toString() {
            return name;
        }
    }
    
}