clustering/ee/spi/src/main/java/org/wildfly/clustering/ee/CompositeIterable.java

@@ -0,0 +1,107 @@
+/*
+ * JBoss, Home of Professional Open Source.
+ * Copyright 2019, Red Hat, Inc., and individual contributors
+ * as indicated by the @author tags. See the copyright.txt file in the
+ * distribution for a full listing of individual contributors.
+ *
+ * This is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * This software is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this software; if not, write to the Free
+ * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
+ */
+
+package org.wildfly.clustering.ee;
+
+import java.util.List;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Iterator;
+
+/**
+ * Used for iterating over an series of iterables, thus avoiding the need to allocate/populate a new list containing all elements.
+ * More efficient than the alternative when the number of iterables is arbitrary and small relative to the size of each iterable.
+ * @author Paul Ferraro
+ */
+public class CompositeIterable<T> implements Iterable<T> {
+
+    private final List<? extends Iterable<? extends T>> iterables;
+
+    /**
+     * Constructs a new composite iterable.
+     * @param iterables a series of iterables
+     */
+    @SafeVarargs
+    public CompositeIterable(Iterable<? extends T>... iterables) {
+        this(Arrays.asList(iterables));
+    }
+
+    /**
+     * Constructs a new composite iterable.
+     * @param iterables a series of iterables
+     */
+    public CompositeIterable(List<? extends Iterable<? extends T>> iterables) {
+        this.iterables = iterables;
+    }
+
+    @Override
+    public Iterator<T> iterator() {
+        List<Iterator<? extends T>> iterators = new ArrayList<>(this.iterables.size());
+        for (Iterable<? extends T> elements : this.iterables) {
+            iterators.add(elements.iterator());
+        }
+        return new CompositeIterator<>(iterators);
+    }
+
+    @Override
+    public int hashCode() {
+        int result = 1;
+        for (Iterable<? extends T> elements : this.iterables) {
+            for (T element : elements) {
+                result = 31 * result + ((element != null) ? element.hashCode() : 0);
+            }
+        }
+        return result;
+    }
+
+    @Override
+    public boolean equals(Object object) {
+        if (!(object instanceof Iterable)) return false;
+        @SuppressWarnings("unchecked")
+        Iterator<Object> otherElements = ((Iterable<Object>) object).iterator();
+        for (Iterable<? extends T> iterable : this.iterables) {
+            Iterator<? extends T> elements = iterable.iterator();
+            while (elements.hasNext() && otherElements.hasNext()) {
+                elements.next().equals(otherElements.next());
+            }
+            if (elements.hasNext()) return false;
+        }
+        return !otherElements.hasNext();
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder builder = new StringBuilder();
+        builder.append('[');
+        Iterator<? extends Iterable<? extends T>> iterables = this.iterables.iterator();
+        while (iterables.hasNext()) {
+            Iterator<? extends T> elements = iterables.next().iterator();
+            while (elements.hasNext()) {
+                if (builder.length() > 1) {
+                    builder.append(',').append(' ');
+                }
+                builder.append(elements.next());
+            }
+        }
+        return builder.append(']').toString();
+    }
+}

clustering/ee/spi/src/main/java/org/wildfly/clustering/ee/CompositeIterator.java

@@ -0,0 +1,69 @@
+/*
+ * JBoss, Home of Professional Open Source.
+ * Copyright 2019, Red Hat, Inc., and individual contributors
+ * as indicated by the @author tags. See the copyright.txt file in the
+ * distribution for a full listing of individual contributors.
+ *
+ * This is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * This software is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this software; if not, write to the Free
+ * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
+ */
+
+package org.wildfly.clustering.ee;
+
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+/**
+ * Iterator that iterates over a series of iterators.
+ * @author Paul Ferraro
+ */
+public class CompositeIterator<E> implements Iterator<E> {
+
+    private final Iterable<? extends Iterator<? extends E>> iterators;
+
+    /**
+     * Constructs a new composite iterator.
+     * @param iterables a series of iterators
+     */
+    @SafeVarargs
+    public CompositeIterator(Iterator<? extends E>... iterators) {
+        this(Arrays.asList(iterators));
+    }
+
+    /**
+     * Constructs a new composite iterator.
+     * @param iterables a series of iterators
+     */
+    public CompositeIterator(Iterable<? extends Iterator<? extends E>> iterators) {
+        this.iterators = iterators;
+    }
+
+    @Override
+    public boolean hasNext() {
+        for (Iterator<? extends E> iterator : this.iterators) {
+            if (iterator.hasNext()) return true;
+        }
+        return false;
+    }
+
+    @Override
+    public E next() {
+        for (Iterator<? extends E> iterator : this.iterators) {
+            if (iterator.hasNext()) return iterator.next();
+        }
+        throw new NoSuchElementException();
+    }
+}