Better Checks 
The Better Checks library provides a lightweight and concise, but powerful way for precodition checking in Java, in particular for method arguments. Checks are written in a fluent way.
Examples:
Check.that(name).matches("hello .*!").hasLengthBetween(0, 20);
Check.that(list).isNullOr().hasSize(0);
Check.that(args).named("arguments").isNotEmpty();
The actual checking methods, such as matches(...) or hasSize(...), all throw an exception if the check fails. The exact type of exception depends on the kind of check that is called but in most cases it is IllegalArgumentException.
Project Website
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