squah-confluent commented on code in PR #17750: URL: https://github.com/apache/kafka/pull/17750#discussion_r1837213912
########## group-coordinator/src/main/java/org/apache/kafka/coordinator/group/modern/UnionSet.java: ########## @@ -0,0 +1,206 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.kafka.coordinator.group.modern; + +import java.lang.reflect.Array; +import java.util.Collection; +import java.util.Iterator; +import java.util.NoSuchElementException; +import java.util.Objects; +import java.util.Set; + +public class UnionSet<T> implements Set<T> { + private final Set<T> largeSet; + private final Set<T> smallSet; + private int size = -1; + + public UnionSet(Set<T> s1, Set<T> s2) { + Objects.requireNonNull(s1); + Objects.requireNonNull(s2); + + if (s1.size() > s2.size()) { + largeSet = s1; + smallSet = s2; + } else { + largeSet = s2; + smallSet = s1; + } + } + + @Override + public int size() { + if (size == -1) { + size = largeSet.size(); + for (T item : smallSet) { + if (!largeSet.contains(item)) { + size++; + } + } + } + return size; + } + + @Override + public boolean isEmpty() { + return largeSet.isEmpty() && smallSet.isEmpty(); + } + + @Override + public boolean contains(Object o) { + return largeSet.contains(o) || smallSet.contains(o); + } + + @Override + public Iterator<T> iterator() { + return new Iterator<T>() { + private final Iterator<T> largeSetIterator = largeSet.iterator(); + private final Iterator<T> smallSetIterator = smallSet.iterator(); + private T next = null; + + @Override + public boolean hasNext() { + if (next != null) return true; + if (largeSetIterator.hasNext()) { + next = largeSetIterator.next(); + return true; + } + while (smallSetIterator.hasNext()) { + next = smallSetIterator.next(); + if (!largeSet.contains(next)) { + return true; + } + } + next = null; + return false; + } + + @Override + public T next() { + if (!hasNext()) throw new NoSuchElementException(); + T result = next; + next = null; + return result; + } + }; + } + + @Override + public Object[] toArray() { + Object[] array = new Object[size()]; + int index = 0; + for (T item : largeSet) { + array[index] = item; + index++; + } + for (T item : smallSet) { + if (!largeSet.contains(item)) { + array[index] = item; + index++; + } + } + return array; + } + + @Override + @SuppressWarnings("unchecked") + public <U> U[] toArray(U[] array) { + int size = size(); + if (array.length < size) { + // Create a new array of the same type as a with the correct size + array = (U[]) Array.newInstance(array.getClass().getComponentType(), size); + } + int index = 0; + for (T item : largeSet) { + array[index] = (U) item; + index++; + } + for (T item: smallSet) { + if (!largeSet.contains(item)) { + array[index] = (U) item; + index++; + } + } + if (array.length > size) { + array[size] = null; + } + return array; + } + + @Override + public boolean add(T t) { + throw new UnsupportedOperationException(); + } + + @Override + public boolean remove(Object o) { + throw new UnsupportedOperationException(); + } + + @Override + public boolean containsAll(Collection<?> c) { + for (Object o : c) { + if (!contains(o)) return false; + } + return true; + } + + @Override + public boolean addAll(Collection<? extends T> c) { + throw new UnsupportedOperationException(); + } + + @Override + public boolean retainAll(Collection<?> c) { + throw new UnsupportedOperationException(); + } + + @Override + public boolean removeAll(Collection<?> c) { + throw new UnsupportedOperationException(); + } + + @Override + public void clear() { + throw new UnsupportedOperationException(); + } + + @Override + public boolean equals(Object o) { + if (this == o) return true; + if (o == null || getClass() != o.getClass()) return false; + + UnionSet<?> unionSet = (UnionSet<?>) o; + + if (!Objects.equals(largeSet, unionSet.largeSet)) return false; + return Objects.equals(smallSet, unionSet.smallSet); + } + + @Override + public int hashCode() { + int result = largeSet != null ? largeSet.hashCode() : 0; + result = 31 * result + (smallSet != null ? smallSet.hashCode() : 0); + return result; + } Review Comment: This might bite us in the future since it breaks the contract for the Set interface. `equals` is supposed to work with any other `Set<>` and `hashCode` is supposed to be "the sum of the hash codes of the elements in the set". https://docs.oracle.com/javase/8/docs/api/java/util/Set.html#equals-java.lang.Object- https://docs.oracle.com/javase/8/docs/api/java/util/Set.html#hashCode-- -- This is an automated message from the Apache Git Service. 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