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From ohe...@apache.org
Subject svn commit: r1026485 - in /commons/proper/lang/trunk/src: main/java/org/apache/commons/lang3/concurrent/ConstantInitializer.java test/java/org/apache/commons/lang3/concurrent/ConstantInitializerTest.java
Date Fri, 22 Oct 2010 20:32:10 GMT
Author: oheger
Date: Fri Oct 22 20:32:09 2010
New Revision: 1026485

URL: http://svn.apache.org/viewvc?rev=1026485&view=rev
Log:
[LANG-653] Added ConstantInitializer class

Added:
    commons/proper/lang/trunk/src/main/java/org/apache/commons/lang3/concurrent/ConstantInitializer.java
  (with props)
    commons/proper/lang/trunk/src/test/java/org/apache/commons/lang3/concurrent/ConstantInitializerTest.java
  (with props)

Added: commons/proper/lang/trunk/src/main/java/org/apache/commons/lang3/concurrent/ConstantInitializer.java
URL: http://svn.apache.org/viewvc/commons/proper/lang/trunk/src/main/java/org/apache/commons/lang3/concurrent/ConstantInitializer.java?rev=1026485&view=auto
==============================================================================
--- commons/proper/lang/trunk/src/main/java/org/apache/commons/lang3/concurrent/ConstantInitializer.java
(added)
+++ commons/proper/lang/trunk/src/main/java/org/apache/commons/lang3/concurrent/ConstantInitializer.java
Fri Oct 22 20:32:09 2010
@@ -0,0 +1,128 @@
+/*
+ * 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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Added: commons/proper/lang/trunk/src/test/java/org/apache/commons/lang3/concurrent/ConstantInitializerTest.java
URL: http://svn.apache.org/viewvc/commons/proper/lang/trunk/src/test/java/org/apache/commons/lang3/concurrent/ConstantInitializerTest.java?rev=1026485&view=auto
==============================================================================
--- commons/proper/lang/trunk/src/test/java/org/apache/commons/lang3/concurrent/ConstantInitializerTest.java
(added)
+++ commons/proper/lang/trunk/src/test/java/org/apache/commons/lang3/concurrent/ConstantInitializerTest.java
Fri Oct 22 20:32:09 2010
@@ -0,0 +1,134 @@
+/*
+ * 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);
+    }
+}

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