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[LANG-653] Added ConstantInitializer class 

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/lang/trunk@1026485 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Oliver Heger 2010-10-22 20:32:09 +00:00
parent 6d992c02da
commit d0b2b05af5
2 changed files with 262 additions and 0 deletions
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128
src/main/java/org/apache/commons/lang3/concurrent/ConstantInitializer.java Normal file
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/*
* 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.commons.lang3.concurrent;
import org.apache.commons.lang3.ObjectUtils;
/**
* <p>
* A very simple implementation of the {@link ConcurrentInitializer} interface
* which always returns the same object.
* </p>
* <p>
* An instance of this class is passed a reference to an object when it is
* constructed. The {@link #get()} method just returns this object. No
* synchronization is required.
* </p>
* <p>
* This class is useful for instance for unit testing or in cases where a
* specific object has to be passed to an object which expects a
* {@link ConcurrentInitializer}.
* </p>
*
* @author Apache Software Foundation
* @version $Id$
* @param <T> the type of the object managed by this initializer
*/
public class ConstantInitializer<T> implements ConcurrentInitializer<T> {
/** Constant for the format of the string representation. */
private static final String FMT_TO_STRING = "ConstantInitializer@%d [ object = %s ]";
/** Stores the managed object. */
private final T object;
/**
* Creates a new instance of {@code ConstantInitializer} and initializes it
* with the object to be managed. The {@code get()} method will always
* return the object passed here. This class does not place any restrictions
* on the object. It may be <b>null</b>, then {@code get()} will return
* <b>null</b>, too.
*
* @param obj the object to be managed by this initializer
*/
public ConstantInitializer(T obj) {
object = obj;
}
/**
* Directly returns the object that was passed to the constructor. This is
* the same object as returned by {@code get()}. However, this method does
* not declare that it throws an exception.
*
* @return the object managed by this initializer
*/
public final T getObject() {
return object;
}
/**
* Returns the object managed by this initializer. This implementation just
* returns the object passed to the constructor.
*
* @return the object managed by this initializer
* @throws ConcurrentException if an error occurs
*/
public T get() throws ConcurrentException {
return getObject();
}
/**
* Returns a hash code for this object. This implementation returns the hash
* code of the managed object.
*
* @return a hash code for this object
*/
@Override
public int hashCode() {
return (getObject() != null) ? getObject().hashCode() : 0;
}
/**
* Compares this object with another one. This implementation returns
* <b>true</b> if and only if the passed in object is an instance of
* {@code ConstantInitializer} which refers to an object equals to the
* object managed by this instance.
*
* @param obj the object to compare to
* @return a flag whether the objects are equal
*/
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (!(obj instanceof ConstantInitializer<?>)) {
return false;
}
ConstantInitializer<?> c = (ConstantInitializer<?>) obj;
return ObjectUtils.equals(getObject(), c.getObject());
}
/**
* Returns a string representation for this object. This string also
* contains a string representation of the object managed by this
* initializer.
*
* @return a string for this object
*/
@Override
public String toString() {
return String.format(FMT_TO_STRING, System.identityHashCode(this),
String.valueOf(getObject()));
}
}

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src/test/java/org/apache/commons/lang3/concurrent/ConstantInitializerTest.java Normal file
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/*
* 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.commons.lang3.concurrent;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;
import java.util.regex.Pattern;
import org.junit.Before;
import org.junit.Test;
/**
* Test class for {@code ConstantInitializer}.
*
* @author Apache Software Foundation
* @version $Id$
*/
public class ConstantInitializerTest {
/** Constant for the object managed by the initializer. */
private static final Integer VALUE = 42;
/** The initializer to be tested. */
private ConstantInitializer<Integer> init;
@Before
public void setUp() throws Exception {
init = new ConstantInitializer<Integer>(VALUE);
}
/**
* Helper method for testing equals() and hashCode().
*
* @param obj the object to compare with the test instance
* @param expected the expected result
*/
private void checkEquals(Object obj, boolean expected) {
assertEquals("Wrong result of equals", expected, init.equals(obj));
if (obj != null) {
assertEquals("Not symmetric", expected, obj.equals(init));
}
if (expected) {
assertEquals("Different hash codes", init.hashCode(),
obj.hashCode());
}
}
/**
* Tests whether the correct object is returned.
*/
@Test
public void testGetObject() {
assertEquals("Wrong object", VALUE, init.getObject());
}
/**
* Tests whether get() returns the correct object.
*/
@Test
public void testGet() throws ConcurrentException {
assertEquals("Wrong object", VALUE, init.get());
}
/**
* Tests equals() if the expected result is true.
*/
@Test
public void testEqualsTrue() {
checkEquals(init, true);
ConstantInitializer<Integer> init2 = new ConstantInitializer<Integer>(
new Integer(VALUE.intValue()));
checkEquals(init2, true);
init = new ConstantInitializer<Integer>(null);
init2 = new ConstantInitializer<Integer>(null);
checkEquals(init2, true);
}
/**
* Tests equals() if the expected result is false.
*/
@Test
public void testEqualsFalse() {
ConstantInitializer<Integer> init2 = new ConstantInitializer<Integer>(
null);
checkEquals(init2, false);
init2 = new ConstantInitializer<Integer>(VALUE + 1);
checkEquals(init2, false);
}
/**
* Tests equals() with objects of other classes.
*/
@Test
public void testEqualsWithOtherObjects() {
checkEquals(null, false);
checkEquals(this, false);
checkEquals(new ConstantInitializer<String>("Test"), false);
}
/**
* Tests the string representation.
*/
@Test
public void testToString() {
String s = init.toString();
Pattern pattern = Pattern
.compile("ConstantInitializer@\\d+ \\[ object = " + VALUE
+ " \\]");
assertTrue("Wrong string: " + s, pattern.matcher(s).matches());
}
/**
* Tests the string representation if the managed object is null.
*/
@Test
public void testToStringNull() {
String s = new ConstantInitializer<Object>(null).toString();
assertTrue("Object not found: " + s, s.indexOf("object = null") > 0);
}
}