10.1 Introduction

In the subsequent chapters, we look at a broad class of objects known as pools. A pool is similar to the Set class studied in Chapter 9, with two main differences: a pool does not necessarily provide a contains() method to test membership, and it allows the same item to appear more than once. The Pool has get() and set() methods as in Fig. 10.1. Pools show up in many places in concurrent systems. For example, in many applications, one or more producer threads produce items to be consumed by one or more consumer threads. These items may be jobs to perform, keystrokes to interpret, purchase orders to execute, or packets to decode. Sometimes, producers are bursty, suddenly and briefly producing items faster than consumers can consume them. To allow consumers to keep up, we can place a buffer between the producers and the consumers. Items produced faster than they can be consumed accumulate in the buffer, from which they are consumed as quickly as possible. Often, pools act as producer-consumer buffers.

1 <b class="bold">public interface</b> Pool {2 <b class="bold">void</b> put(T item);3 T get();4 }

Pools come in several varieties.

• A pool can be bounded or unbounded. A bounded pool holds a limited number of items. This limit is called its capacity. By contrast, an unbounded pool can hold any number of items. Bounded pools are useful when we want...