3.5 Added takeLastBuffer

Author: Froussios

Part 3 - Taming the sequence/5. Time-shifted sequences.md

@@ -181,6 +181,61 @@ Output
 
 We've created an `Observable.interval` that signals the opening of a new buffer every 250ms. Because observables created with `interval` do not immediately emit a value, the first values were lost. For the closing of a buffer, we provided a lambda function that took every value emitted by our buffer-opening observable. The values generated by `interval` are the natural progression 1,2,3... but that doesn't matter, because we discarded that value. Such an example would be too complicated. Instead, we just created an observable that waits 200ms and then emits a single value. That means that each buffer last exactly 200ms, similarily to when buffering by time.
 
+### takeLastBuffer
+
+We have already seen the [takeLast](/Part%202%20-%20Sequence%20Basics/2.%20Reducing%20a%20sequence.md#skiplast-and-takelast) operator, which returns the last N number of items. Internally, `takeLast` needs to buffer items and re-emits them when the source sequence ends. The `takeLastBuffer` operator returns the last elements as one buffer.
+
+#### By count
+
+![](https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/takeLastBuffer.png)
+
+`takeLastBuffer` by count will emit the last `N` elements in a list.
+
+```java
+Observable.range(0, 5)
+	.takeLastBuffer(2)
+	.subscribe(System.out::println);
+```
+Output
+```
+[3, 4]
+```
+
+#### By time
+
+![](https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/takeLastBuffer.tn.png)
+
+`takeLastBuffer` by time will emit, as a buffer, the items that were received during the specified timespan. The timespan has the specified length and ends at the end of the source sequence.
+
+```java
+Observable.interval(100, TimeUnit.MILLISECONDS)
+	.take(5)
+	.takeLastBuffer(200, TimeUnit.MILLISECONDS)
+	.subscribe(System.out::println);
+```
+Output
+```
+[2, 3, 4]
+```
+
+#### By count and time
+
+The buffer emitted by this overload of `takeLastBuffer` will contain items that were emitted over the specified timespan before the end. If this window contains more than the specified number of items, the buffer will contain the last `N` items.
+
+```java
+Observable.interval(100, TimeUnit.MILLISECONDS)
+	.take(5)
+	.takeLastBuffer(2, 200, TimeUnit.MILLISECONDS)
+	.subscribe(System.out::println);
+```
+Output
+```
+[3, 4]
+```
+
+As we saw in the previous example, the last 200ms include three values. With `.takeLastBuffer(2, 200, TimeUnit.MILLISECONDS)` we specified that we want values from the last 200ms, but no more than 2 values. For that reason, we only get the last two values.
+
+
 ## Delay
 
 `delay`, as the name suggests, will postpone the emission of values for a specified amount of time. The are two ways to do that. One is by storing values until you are ready to emit them. The other is to delay the subscription to observable.