[COLLECTIONS-399] Added get(index) method to BoundedFifoBuffer.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/collections/trunk@1351852 13f79535-47bb-0310-9956-ffa450edef68

src/main/java/org/apache/commons/collections/buffer/BoundedFifoBuffer.java

@@ -131,7 +131,7 @@ public class BoundedFifoBuffer<E> extends AbstractCollection<E>
      * Write the buffer out using a custom routine.
      *
      * @param out  the output stream
-     * @throws IOException
+     * @throws IOException if an I/O error occurs while writing to the output stream
      */
     private void writeObject(ObjectOutputStream out) throws IOException {
         out.defaultWriteObject();
@@ -145,8 +145,8 @@ public class BoundedFifoBuffer<E> extends AbstractCollection<E>
      * Read the buffer in using a custom routine.
      *
      * @param in  the input stream
-     * @throws IOException
-     * @throws ClassNotFoundException
+     * @throws IOException if an I/O error occurs while writing to the output stream
+     * @throws ClassNotFoundException if the class of a serialized object can not be found
      */
     @SuppressWarnings("unchecked")
     private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
@@ -269,6 +269,22 @@ public class BoundedFifoBuffer<E> extends AbstractCollection<E>
         return elements[start];
     }
 
+    /**
+     * Returns the element at the specified position in this buffer.
+     *
+     * @param index the position of the element in the buffer
+     * @return the element at position {@code index}
+     * @throws NoSuchElementException if the requested position is outside the range [0, size)
+     */
+    public E get(int index) {
+        if (index < 0 || index >= size()) {
+            throw new NoSuchElementException();
+        }
+        
+        final int idx = (start + index) % maxElements;
+        return elements[idx];
+    }
+ 
     /**
      * Removes the least recently inserted element from this buffer.
      *

src/test/java/org/apache/commons/collections/buffer/TestBoundedFifoBuffer.java

@@ -19,6 +19,7 @@ package org.apache.commons.collections.buffer;
 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
+import java.util.NoSuchElementException;
 
 import junit.framework.Test;
 
@@ -172,6 +173,44 @@ public class TestBoundedFifoBuffer<E> extends AbstractTestCollection<E> {
         fail();
     }
     
+    /**
+     * Tests that the get(index) method correctly throws an exception.
+     */
+    public void testGetException() {
+        resetFull();
+        try {
+            getCollection().get(-1);
+            fail();
+        } catch (NoSuchElementException ex) {
+            // expected
+        }
+        
+        try {
+            getCollection().get(getCollection().size());
+            fail();
+        } catch (NoSuchElementException ex) {
+            // expected
+        }
+    }
+
+    public void testGetIndex() {
+        resetFull();
+        
+        BoundedFifoBuffer<E> buffer = getCollection();
+        List<E> confirmed = getConfirmed();
+        for (int i = 0; i < confirmed.size(); i++) {
+            assertEquals(confirmed.get(i), buffer.get(i));
+        }
+
+        // remove the first two elements and check again
+        buffer.remove();
+        buffer.remove();
+        
+        for (int i = 0; i < buffer.size(); i++) {
+            assertEquals(confirmed.get(i + 2), buffer.get(i));
+        }        
+    }
+
     @Override
     public String getCompatibilityVersion() {
         return "3.1";

src/test/java/org/apache/commons/collections/buffer/TestCircularFifoBuffer.java

@@ -415,6 +415,24 @@ public class TestCircularFifoBuffer<E> extends AbstractTestCollection<E> {
         assertEquals(true, b3.contains("c"));
     }
 
+    public void testGetIndex() {
+        resetFull();
+        
+        CircularFifoBuffer<E> buffer = getCollection();
+        List<E> confirmed = getConfirmed();
+        for (int i = 0; i < confirmed.size(); i++) {
+            assertEquals(confirmed.get(i), buffer.get(i));
+        }
+
+        // remove the first two elements and check again
+        buffer.remove();
+        buffer.remove();
+        
+        for (int i = 0; i < buffer.size(); i++) {
+            assertEquals(confirmed.get(i + 2), buffer.get(i));
+        }        
+    }
+
     @Override
     public String getCompatibilityVersion() {
         return "3.1";