rename epublib to book,库里面包含umd

book/src/main/java/me/ag2s/epublib/util/CollectionUtil.java

@@ -0,0 +1,71 @@
+package me.ag2s.epublib.util;
+
+import java.util.Collection;
+import java.util.Enumeration;
+import java.util.Iterator;
+import java.util.List;
+
+public class CollectionUtil {
+
+  /**
+   * Wraps an Enumeration around an Iterator
+   * @author paul.siegmann
+   *
+   * @param <T>
+   */
+  private static class IteratorEnumerationAdapter<T> implements Enumeration<T> {
+
+    private final Iterator<T> iterator;
+
+    public IteratorEnumerationAdapter(Iterator<T> iter) {
+      this.iterator = iter;
+    }
+
+    @Override
+    public boolean hasMoreElements() {
+      return iterator.hasNext();
+    }
+
+    @Override
+    public T nextElement() {
+      return iterator.next();
+    }
+  }
+
+  /**
+   * Creates an Enumeration out of the given Iterator.
+   * @param <T>  g
+   * @param it g
+   * @return an Enumeration created out of the given Iterator.
+   */
+  @SuppressWarnings("unused")
+  public static <T> Enumeration<T> createEnumerationFromIterator(
+      Iterator<T> it) {
+    return new IteratorEnumerationAdapter<>(it);
+  }
+
+
+  /**
+   * Returns the first element of the list, null if the list is null or empty.
+   *
+   * @param <T> f
+   * @param list f
+   * @return the first element of the list, null if the list is null or empty.
+   */
+  public static <T> T first(List<T> list) {
+    if (list == null || list.isEmpty()) {
+      return null;
+    }
+    return list.get(0);
+  }
+
+  /**
+   * Whether the given collection is null or has no elements.
+   *
+   * @param collection g
+   * @return Whether the given collection is null or has no elements.
+   */
+  public static boolean isEmpty(Collection<?> collection) {
+    return collection == null || collection.isEmpty();
+  }
+}