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OAK-11571: commons: add Closer class (similar to Guava Closer) (#2181)
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‎oak-commons/pom.xml‎

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@@ -56,7 +56,8 @@
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org.apache.jackrabbit.oak.commons.log,
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org.apache.jackrabbit.oak.commons.sort,
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org.apache.jackrabbit.oak.commons.properties,
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org.apache.jackrabbit.oak.commons.jdkcompat
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org.apache.jackrabbit.oak.commons.jdkcompat,
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org.apache.jackrabbit.oak.commons.pio
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</Export-Package>
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</instructions>
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</configuration>

‎oak-commons/src/main/java/org/apache/jackrabbit/oak/commons/pio/Closer.java‎

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/*
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing,
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* software distributed under the License is distributed on an
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* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations
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* under the License.
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*/
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package org.apache.jackrabbit.oak.commons.pio;
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import org.jetbrains.annotations.NotNull;
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import org.jetbrains.annotations.Nullable;
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import java.io.Closeable;
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import java.io.IOException;
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import java.util.ArrayDeque;
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import java.util.Deque;
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import java.util.Objects;
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/**
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* Convenience utility to close a list of {@link Closeable}s in reverse order,
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* suppressing all but the first exception to occur.
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* <p>
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* Inspired by and replacing Guava's Closer.
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*/
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public class Closer implements Closeable {
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private Closer() {
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// no instances for you
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}
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// stack of closeables to close, in general will be few
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private final Deque<Closeable> closeables = new ArrayDeque<>(3);
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// flag set by rethrow method
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private boolean suppressExceptionsOnClose = false;
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/**
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* Create instance of Closer.
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*/
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public static Closer create() {
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return new Closer();
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}
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/**
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* Add a {@link Closeable} to the list.
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* @param closeable {@link Closeable} object to be added
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* @return the closeable param
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*/
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public @Nullable <C extends Closeable> C register(@Nullable C closeable) {
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if (closeable != null) {
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closeables.add(closeable);
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}
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return closeable;
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}
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/**
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* Closes the set of {@link Closeable}s in reverse order.
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* <p>
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* Swallows all exceptions except the first that
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* was thrown.
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* <p>
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* If {@link #rethrow} was called before, even the first
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* exception will be suppressed.
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*/
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public void close() throws IOException {
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// keep track of the IOException to throw
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Throwable toThrow = null;
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// close all in reverse order
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while (!closeables.isEmpty()) {
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Closeable closeable = closeables.removeLast();
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try {
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closeable.close();
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} catch (Throwable exception) {
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// remember the first one that occurred
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if (toThrow == null) {
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toThrow = exception;
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}
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}
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}
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// exceptions are suppressed when retrow was called
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if (!suppressExceptionsOnClose && toThrow != null) {
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// due to the contract of Closeable, the exception is either
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// a checked IOException or an unchecked exception
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if (toThrow instanceof IOException) {
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throw (IOException) toThrow;
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} else {
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throw (RuntimeException) toThrow;
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}
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}
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}
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/**
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* Sets a flag indicating that this method was called, then rethrows the
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* given exception (potentially wrapped into {@link Error} or {@link RuntimeException}).
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* <p>
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* {@link #close()} will not throw when this method was called before.
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* @return never returns
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* @throws IOException wrapping the input, when needed
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*/
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public RuntimeException rethrow(@NotNull Throwable throwable) throws IOException {
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Objects.requireNonNull(throwable);
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suppressExceptionsOnClose = true;
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if (throwable instanceof IOException) {
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throw (IOException) throwable;
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} else if (throwable instanceof RuntimeException) {
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throw (RuntimeException) throwable;
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} else if (throwable instanceof Error) {
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throw (Error) throwable;
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} else {
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throw new RuntimeException(throwable);
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}
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}
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}

‎oak-commons/src/main/java/org/apache/jackrabbit/oak/commons/pio/package-info.java‎

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/*
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing,
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* software distributed under the License is distributed on an
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* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations
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* under the License.
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*/
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/**
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* Internal ("private") utilities related to IO..
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*/
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@Internal(since = "1.0.0")
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@Version("1.0.0")
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package org.apache.jackrabbit.oak.commons.pio;
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import org.apache.jackrabbit.oak.commons.annotations.Internal;
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import org.osgi.annotation.versioning.Version;
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‎oak-commons/src/test/java/org/apache/jackrabbit/oak/commons/pio/CloserTest.java‎

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/*
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing,
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* software distributed under the License is distributed on an
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* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations
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* under the License.
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*/
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package org.apache.jackrabbit.oak.commons.pio;
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import org.junit.Test;
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import java.io.Closeable;
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import java.io.IOException;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.concurrent.atomic.AtomicBoolean;
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import static org.junit.Assert.assertEquals;
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import static org.junit.Assert.assertNull;
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import static org.junit.Assert.assertThrows;
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import static org.junit.Assert.assertTrue;
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import static org.junit.Assert.fail;
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public class CloserTest {
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@Test
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public void testCloserOrder() throws IOException {
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// shows closes in reverse order
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int cnt = 2;
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List<Integer> order = new ArrayList<>();
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Closer closer = Closer.create();
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for (int i = 0; i < cnt; i++) {
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Integer val = i;
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Closeable c = new Closeable() {
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final Integer c = val;
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@Override
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public void close() {
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order.add(c);
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}
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};
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closer.register(c);
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}
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closer.close();
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assertEquals(1, (int)order.get(0));
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assertEquals(0, (int)order.get(1));
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}
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@Test
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public void testCloserWithTryWithResources() throws IOException {
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// check cloesable behavior of Closer
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AtomicBoolean wasClosed = new AtomicBoolean(false);
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try (Closer closer = Closer.create()) {
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closer.register(() -> wasClosed.set(true));
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}
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assertTrue("closeable should be closed by try-w-resources", wasClosed.get());
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}
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@Test
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public void testCloseableThrowsRuntimeException() {
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Closer closer = Closer.create();
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closer.register(() -> {
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throw new RuntimeException();
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});
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assertThrows(RuntimeException.class, closer::close);
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}
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@Test
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public void testWhichThrows() throws IOException {
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// shows which exception is not suppressed
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int cnt = 2;
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Closer closer = Closer.create();
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for (int i = 0; i < cnt; i++) {
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Integer val = i;
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Closeable c = new Closeable() {
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final Integer c = val;
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@Override
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public void close() throws IOException {
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throw new IOException("" + c);
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}
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};
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closer.register(c);
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}
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try {
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closer.close();
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fail("should throw");
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} catch (IOException ex) {
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assertEquals("1", ex.getMessage());
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}
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}
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@Test
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public void testRethrowRuntime() {
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try {
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Closer closer = Closer.create();
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try {
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closer.register(() -> {
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throw new IOException("checked");
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});
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throw new RuntimeException("unchecked");
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} catch (Throwable t) {
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throw closer.rethrow(t);
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} finally {
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closer.close();
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}
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} catch (Exception ex) {
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assertTrue(
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"should throw the (wrapped) unchecked exception, but got " +
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ex.getMessage(),
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ex.getMessage().contains("unchecked"));
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}
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}
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@Test
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public void testRethrowChecked() throws IOException {
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try {
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Closer closer = Closer.create();
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try {
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closer.register(() -> {
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throw new IOException("checked");
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});
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throw new InterruptedException("interrupted");
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} catch (Throwable t) {
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throw closer.rethrow(t);
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} finally {
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closer.close();
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}
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} catch (RuntimeException ex) {
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assertTrue("should throw the (wrapped) exception",
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ex.getCause() instanceof InterruptedException);
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}
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}
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@Test
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public void compareClosers() {
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// when rethrow was called, IOExceptions that happened upon close will be swallowed
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com.google.common.io.Closer guavaCloser = com.google.common.io.Closer.create();
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Closer oakCloser = Closer.create();
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try {
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throw oakCloser.rethrow(new InterruptedException());
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} catch (Exception e) {}
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try {
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throw guavaCloser.rethrow(new InterruptedException());
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} catch (Exception e) {}
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try {
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oakCloser.close();
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} catch (Exception e) {
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fail("should not throw but got: " + e);
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}
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try {
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guavaCloser.close();
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} catch (Exception e) {
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fail("should not throw but got: " + e);
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}
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}
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@Test
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public void compareClosers2() {
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// when rethrow was called, Exceptions that happened upon close will be swallowed
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com.google.common.io.Closer guavaCloser = com.google.common.io.Closer.create();
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Closer oakCloser = Closer.create();
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try {
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throw oakCloser.rethrow(new InterruptedException());
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} catch (Exception e) {}
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try {
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throw guavaCloser.rethrow(new InterruptedException());
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} catch (Exception e) {}
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try {
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oakCloser.register(() -> { throw new RuntimeException(); });
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oakCloser.close();
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} catch (Exception e) {
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fail("should not throw but got: " + e);
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}
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try {
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guavaCloser.register(() -> { throw new RuntimeException(); });
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guavaCloser.close();
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} catch (Exception e) {
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fail("should not throw but got: " + e);
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}
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}
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}

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