LMS-1665 introduce Counters with tests.

SVN: 17487

common/source/java/ch/systemsx/cisd/common/utilities/Counters.java

+/*
+ * Copyright 2010 ETH Zuerich, CISD
+ *
+ * Licensed 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 ch.systemsx.cisd.common.utilities;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * A set of counters identified by objects of type <code>T</code>.
+ *
+ * @author Franz-Josef Elmer
+ */
+public class Counters<T>
+{
+    private static final class Counter
+    {
+        private int count;
+
+        public int increment()
+        {
+            return ++count;
+        }
+    }
+    
+    private final Map<T, Counter> counters = new HashMap<T, Counter>();
+  
+    /**
+     * Returns how often method {@link #count(Object)} has been invoked for the specified object.
+     */
+    public int getCountOf(T object)
+    {
+        Counter counter = counters.get(object);
+        return counter == null ? 0 : counter.count;
+    }
+    
+    /**
+     * Counts the specified object and return how often it has already been counted.
+     */
+    public int count(T object)
+    {
+        Counter counter = counters.get(object);
+        if (counter == null)
+        {
+            counter = new Counter();
+            counters.put(object, counter);
+        }
+        return counter.increment();
+    }
+}

common/sourceTest/java/ch/systemsx/cisd/common/utilities/CountersTest.java

+/*
+ * Copyright 2010 ETH Zuerich, CISD
+ *
+ * Licensed 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 ch.systemsx.cisd.common.utilities;
+
+import org.testng.AssertJUnit;
+import org.testng.annotations.Test;
+
+/**
+ * 
+ *
+ * @author Franz-Josef Elmer
+ */
+public class CountersTest extends AssertJUnit
+{
+    @Test
+    public void test()
+    {
+        Counters<String> counters = new Counters<String>();
+        
+        assertEquals(0, counters.getCountOf("a"));
+        assertEquals(1, counters.count("a"));
+        assertEquals(1, counters.getCountOf("a"));
+        assertEquals(1, counters.count("b"));
+        assertEquals(1, counters.getCountOf("a"));
+        assertEquals(1, counters.getCountOf("b"));
+        assertEquals(2, counters.count("a"));
+        assertEquals(3, counters.count("a"));
+        assertEquals(3, counters.getCountOf("a"));
+        assertEquals(1, counters.getCountOf("b"));
+    }
+}