added LimitedSortedSet

scm-core/src/main/java/sonia/scm/collect/LimitedSortedSet.java

@@ -0,0 +1,143 @@
+/**
+ * Copyright (c) 2010, Sebastian Sdorra All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer. 2. Redistributions in
+ * binary form must reproduce the above copyright notice, this list of
+ * conditions and the following disclaimer in the documentation and/or other
+ * materials provided with the distribution. 3. Neither the name of SCM-Manager;
+ * nor the names of its contributors may be used to endorse or promote products
+ * derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR
+ * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * http://bitbucket.org/sdorra/scm-manager
+ *
+ */
+
+
+
+package sonia.scm.collect;
+
+//~--- non-JDK imports --------------------------------------------------------
+
+import com.google.common.collect.ForwardingSortedSet;
+import com.google.common.collect.Sets;
+
+//~--- JDK imports ------------------------------------------------------------
+
+import java.util.Collection;
+import java.util.Comparator;
+import java.util.SortedSet;
+import java.util.TreeSet;
+
+/**
+ * A sorted set which is limited to a specified maximum size. If the maximum
+ * size is reached the last element is removed from the set.
+ *
+ * @author Sebastian Sdorra
+ *
+ * @param <E>
+ * @since 1.32
+ */
+public class LimitedSortedSet<E> extends ForwardingSortedSet<E>
+{
+
+  /**
+   * Constructs a new set with the specified maximum.
+   *
+   *
+   * @param maxSize maximum size of the set
+   */
+  public LimitedSortedSet(int maxSize)
+  {
+    this.treeSet = Sets.newTreeSet();
+    this.maxSize = maxSize;
+  }
+
+  /**
+   * Constructs a new set with the specified comparator and maximum.
+   *
+   *
+   *
+   * @param comparator comparator to order the set
+   * @param maxSize maximum size of the set
+   */
+  public LimitedSortedSet(Comparator<E> comparator, int maxSize)
+  {
+    this.treeSet = Sets.newTreeSet(comparator);
+    this.maxSize = maxSize;
+  }
+
+  //~--- methods --------------------------------------------------------------
+
+  /**
+   * {@inheritDoc}
+   */
+  @Override
+  public boolean add(E o)
+  {
+    boolean added = super.add(o);
+
+    cleanUp();
+
+    return added;
+  }
+
+  /**
+   * {@inheritDoc}
+   */
+  @Override
+  public boolean addAll(Collection<? extends E> c)
+  {
+    boolean added = super.addAll(c);
+
+    cleanUp();
+
+    return added;
+  }
+
+  /**
+   * Returns the underlying delegate set.
+   *
+   *
+   * @return delegate set
+   */
+  @Override
+  protected SortedSet<E> delegate()
+  {
+    return treeSet;
+  }
+
+  /**
+   * Remove the last entries, if the maximum size is reached.
+   *
+   */
+  private void cleanUp()
+  {
+    while (size() > maxSize)
+    {
+      remove(last());
+    }
+  }
+
+  //~--- fields ---------------------------------------------------------------
+
+  /** maximum size of the set */
+  private int maxSize;
+
+  /** delegate set */
+  private TreeSet treeSet;
+}