[LANG-678] Added support for ConcurrentMap.putIfAbsent() to ConcurrentUtils.
git-svn-id: https://svn.apache.org/repos/asf/commons/proper/lang/trunk@1071401 13f79535-47bb-0310-9956-ffa450edef68
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Oliver Heger
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536ea90fc0
commit
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@ -16,6 +16,7 @@
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*/
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package org.apache.commons.lang3.concurrent;
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import java.util.concurrent.ConcurrentMap;
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import java.util.concurrent.ExecutionException;
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import java.util.concurrent.Future;
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import java.util.concurrent.TimeUnit;
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@ -204,6 +205,105 @@ public class ConcurrentUtils {
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}
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}
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//-----------------------------------------------------------------------
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/**
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* <p>
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* Puts a value in the specified {@code ConcurrentMap} if the key is not yet
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* present. This method works similar to the {@code putIfAbsent()} method of
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* the {@code ConcurrentMap} interface, but the value returned is different.
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* Basically, this method is equivalent to the following code fragment:
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*
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* <pre>
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* if (!map.containsKey(key)) {
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* map.put(key, value);
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* return value;
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* } else {
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* return map.get(key);
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* }
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* </pre>
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*
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* except that the action is performed atomically. So this method always
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* returns the value which is stored in the map.
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* </p>
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* <p>
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* This method is <b>null</b>-safe: It accepts a <b>null</b> map as input
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* without throwing an exception. In this case the return value is
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* <b>null</b>, too.
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* </p>
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*
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* @param <K> the type of the keys of the map
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* @param <V> the type of the values of the map
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* @param map the map to be modified
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* @param key the key of the value to be added
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* @param value the value to be added
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* @return the value stored in the map after this operation
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*/
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public static <K, V> V putIfAbsent(ConcurrentMap<K, V> map, K key, V value) {
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if (map == null) {
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return null;
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}
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V result = map.putIfAbsent(key, value);
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return (result != null) ? result : value;
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}
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/**
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* Checks if a concurrent map contains a key and creates a corresponding
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* value if not. This method first checks the presence of the key in the
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* given map. If it is already contained, its value is returned. Otherwise
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* the {@code get()} method of the passed in {@link ConcurrentInitializer}
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* is called. With the resulting object
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* {@link #putIfAbsent(ConcurrentMap, Object, Object)} is called. This
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* handles the case that in the meantime another thread has added the key to
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* the map. Both the map and the initializer can be <b>null</b>; in this
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* case this method simply returns <b>null</b>.
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*
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* @param <K> the type of the keys of the map
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* @param <V> the type of the values of the map
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* @param map the map to be modified
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* @param key the key of the value to be added
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* @param init the {@link ConcurrentInitializer} for creating the value
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* @return the value stored in the map after this operation; this may or may
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* not be the object created by the {@link ConcurrentInitializer}
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* @throws ConcurrentException if the initializer throws an exception
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*/
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public static <K, V> V createIfAbsent(ConcurrentMap<K, V> map, K key,
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ConcurrentInitializer<V> init) throws ConcurrentException {
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if (map == null || init == null) {
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return null;
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}
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V value = map.get(key);
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if (value == null) {
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return putIfAbsent(map, key, init.get());
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}
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return value;
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}
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/**
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* Checks if a concurrent map contains a key and creates a corresponding
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* value if not, suppressing checked exceptions. This method calls
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* {@code createIfAbsent()}. If a {@link ConcurrentException} is thrown, it
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* is caught and re-thrown as a {@link ConcurrentRuntimeException}.
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*
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* @param <K> the type of the keys of the map
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* @param <V> the type of the values of the map
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* @param map the map to be modified
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* @param key the key of the value to be added
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* @param init the {@link ConcurrentInitializer} for creating the value
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* @return the value stored in the map after this operation; this may or may
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* not be the object created by the {@link ConcurrentInitializer}
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* @throws ConcurrentRuntimeException if the initializer throws an exception
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*/
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public static <K, V> V createIfAbsentUnchecked(ConcurrentMap<K, V> map,
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K key, ConcurrentInitializer<V> init) {
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try {
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return createIfAbsent(map, key, init);
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} catch (ConcurrentException cex) {
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throw new ConcurrentRuntimeException(cex.getCause());
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}
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}
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//-----------------------------------------------------------------------
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/**
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* <p>
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@ -23,6 +23,8 @@ import static org.junit.Assert.assertSame;
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import static org.junit.Assert.assertTrue;
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import static org.junit.Assert.fail;
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import java.util.concurrent.ConcurrentHashMap;
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import java.util.concurrent.ConcurrentMap;
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import java.util.concurrent.ExecutionException;
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import java.util.concurrent.Future;
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import java.util.concurrent.TimeUnit;
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@ -405,4 +407,142 @@ public class ConcurrentUtilsTest {
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assertFalse(test.cancel(false));
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}
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//-----------------------------------------------------------------------
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/**
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* Tests putIfAbsent() if the map contains the key in question.
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*/
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@Test
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public void testPutIfAbsentKeyPresent() {
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final String key = "testKey";
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final Integer value = 42;
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ConcurrentMap<String, Integer> map = new ConcurrentHashMap<String, Integer>();
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map.put(key, value);
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assertEquals("Wrong result", value,
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ConcurrentUtils.putIfAbsent(map, key, 0));
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assertEquals("Wrong value in map", value, map.get(key));
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}
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/**
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* Tests putIfAbsent() if the map does not contain the key in question.
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*/
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@Test
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public void testPutIfAbsentKeyNotPresent() {
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final String key = "testKey";
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final Integer value = 42;
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ConcurrentMap<String, Integer> map = new ConcurrentHashMap<String, Integer>();
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assertEquals("Wrong result", value,
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ConcurrentUtils.putIfAbsent(map, key, value));
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assertEquals("Wrong value in map", value, map.get(key));
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}
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/**
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* Tests putIfAbsent() if a null map is passed in.
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*/
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@Test
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public void testPutIfAbsentNullMap() {
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assertNull("Wrong result",
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ConcurrentUtils.putIfAbsent(null, "test", 100));
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}
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/**
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* Tests createIfAbsent() if the key is found in the map.
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*/
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@Test
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public void testCreateIfAbsentKeyPresent() throws ConcurrentException {
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@SuppressWarnings("unchecked")
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ConcurrentInitializer<Integer> init = EasyMock
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.createMock(ConcurrentInitializer.class);
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EasyMock.replay(init);
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final String key = "testKey";
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final Integer value = 42;
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ConcurrentMap<String, Integer> map = new ConcurrentHashMap<String, Integer>();
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map.put(key, value);
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assertEquals("Wrong result", value,
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ConcurrentUtils.createIfAbsent(map, key, init));
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assertEquals("Wrong value in map", value, map.get(key));
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EasyMock.verify(init);
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}
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/**
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* Tests createIfAbsent() if the map does not contain the key in question.
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*/
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@Test
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public void testCreateIfAbsentKeyNotPresent() throws ConcurrentException {
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@SuppressWarnings("unchecked")
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ConcurrentInitializer<Integer> init = EasyMock
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.createMock(ConcurrentInitializer.class);
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final String key = "testKey";
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final Integer value = 42;
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EasyMock.expect(init.get()).andReturn(value);
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EasyMock.replay(init);
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ConcurrentMap<String, Integer> map = new ConcurrentHashMap<String, Integer>();
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assertEquals("Wrong result", value,
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ConcurrentUtils.createIfAbsent(map, key, init));
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assertEquals("Wrong value in map", value, map.get(key));
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EasyMock.verify(init);
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}
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/**
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* Tests createIfAbsent() if a null map is passed in.
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*/
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@Test
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public void testCreateIfAbsentNullMap() throws ConcurrentException {
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@SuppressWarnings("unchecked")
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ConcurrentInitializer<Integer> init = EasyMock
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.createMock(ConcurrentInitializer.class);
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EasyMock.replay(init);
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assertNull("Wrong result",
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ConcurrentUtils.createIfAbsent(null, "test", init));
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EasyMock.verify(init);
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}
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/**
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* Tests createIfAbsent() if a null initializer is passed in.
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*/
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@Test
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public void testCreateIfAbsentNullInit() throws ConcurrentException {
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ConcurrentMap<String, Integer> map = new ConcurrentHashMap<String, Integer>();
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final String key = "testKey";
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final Integer value = 42;
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map.put(key, value);
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assertNull("Wrong result",
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ConcurrentUtils.createIfAbsent(map, key, null));
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assertEquals("Map was changed", value, map.get(key));
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}
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/**
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* Tests createIfAbsentUnchecked() if no exception is thrown.
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*/
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@Test
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public void testCreateIfAbsentUncheckedSuccess() {
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final String key = "testKey";
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final Integer value = 42;
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ConcurrentMap<String, Integer> map = new ConcurrentHashMap<String, Integer>();
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assertEquals("Wrong result", value,
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ConcurrentUtils.createIfAbsentUnchecked(map, key,
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new ConstantInitializer<Integer>(value)));
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assertEquals("Wrong value in map", value, map.get(key));
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}
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/**
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* Tests createIfAbsentUnchecked() if an exception is thrown.
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*/
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@Test
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public void testCreateIfAbsentUncheckedException()
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throws ConcurrentException {
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@SuppressWarnings("unchecked")
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ConcurrentInitializer<Integer> init = EasyMock
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.createMock(ConcurrentInitializer.class);
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Exception ex = new Exception();
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EasyMock.expect(init.get()).andThrow(new ConcurrentException(ex));
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EasyMock.replay(init);
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try {
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ConcurrentUtils.createIfAbsentUnchecked(
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new ConcurrentHashMap<String, Integer>(), "test", init);
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fail("Exception not thrown!");
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} catch (ConcurrentRuntimeException crex) {
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assertEquals("Wrong cause", ex, crex.getCause());
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}
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EasyMock.verify(init);
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}
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}
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