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This noncompliant example is comprised of an ArrayList collection which is non-thread-safe by default. There is, however, a way around this drawback. Most thread-unsafe classes have a synchronized thread-safe version, for example, Collections.synchronizedList being is a good substitute for ArrayList and Collections.synchronizedMap is a good alternative to HashMap. One pitfall described in the coming lines, remains to be addressed even when the particular Collection offers thread-safety benefits.
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