J2EE Design Patterns

Colophon

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The animal on the cover of J2EE Design Patterns is a mollusk. Oysters, squid, and snails all belong to this group of invertebrates (phylum Mollusca ), which can be found in streams and oceans as well as on land. There are herbivorous, carnivorous, scavenging, and parasitic mollusks. Most possess a mantle , a layer of tissue that protects the animal’s gills or lungs, and often produces a calcareous shell. They have a powerful, muscular foot section that they use for moving around.

Aquatic mollusks breathe through gills, and filter water for their food, which includes plankton and other single-cell plants and animals. Scientists have found that filter-feeding mollusks can serve as a benchmark of the degree of pollution in a body of water. The contaminants are a health hazard to the mollusks, and also to the people who may eat them.

There are three main classes of mollusks: the bivalves, the gastropods, and the cephalopods. The bivalve class is made up of mollusks with two hinged shells, such as oysters, clams, and scallops. Snails and slugs are members of the largest class of mollusks, the gastropods, which includes over 40,000 species. Gastropods often have a single, spiral-shaped shell, although some species have none. Cephalopods ...