Java Cookbook takes a “recipes” approach: each section gives a problem, a solution, and a discussion, aimed at developers who already know the basics of Java but want practical, usable code examples to solve real-world problems.
javacook.darwinsys.com
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Topics covered include: compiling and running Java, interacting with the environment and OS, string/text manipulations, regular expressions, numbers/dates/times, data structures and collections, object-oriented techniques, I/O, threading, networking, packages and packaging, distributed Java (RMI), and much more.
O'Reilly Media
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The emphasis is not on teaching Java from the very beginning (syntax, etc) but on delivering useful code snippets and solutions (“recipes”) that can be incorporated into other programs. The author writes: “The idea is to focus on things that are useful, tricky, or both.”
Google Books
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This makes it particularly valuable as a reference for intermediate Java developers who have moved past “Hello World” and are facing unfamiliar or tricky API problems. It serves as a “jumping-off place” rather than a full tutorial.