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- java.util
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This package defines many important and commonly used utility classes, the most important of which are the various Collection , Set , List , and Map implementations . In Java 5.0 the collection classes and interfaces have been converted into generic types.
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- java.util.concurrent
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This package includes utilities for concurrent programming, including threadsafe collection classes, threadpool implementations, and synchronizer utilities.
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- java.util.concurrent.atomic
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This package includes classes that define atomic operations on primitive values or object references.
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- java.util.concurrent.locks
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This package contains low-level lock and condition utilities.
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- java.util.jar
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This package defines classes for reading and writing JAR (Java ARchive) files. They are based on the classes of the java.util.zip package.
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- java.util.logging
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This package defines a powerful and flexible logging API for Java applications.
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- java.util.prefs
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This package allows applications to set and query persistent values for user -specific preferences or system-wide configuration parameters.
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- java.util.regex
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This package defines an API for textual pattern matching using regular expressions.
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- java.util.zip
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This package defines classes for reading and writing ZIP files and for compressing and uncompressing data using the "gzip" format.