### Question:
CacheManager implements CacheManagerBean { public ObjectCache acquire(final @NonNull String uniqueCacheIdentifier) { CacheIdentifier prefix = CACHE_IDS.get(uniqueCacheIdentifier); if (prefix == null) { prefix = new CacheIdentifier(CACHE_ID_SEQ.incrementAndGet()); CacheIdentifier existing = CACHE_IDS.putIfAbsent(uniqueCacheIdentifier, prefix); if (existing != null) { prefix = existing; } } return CACHES.acquire(prefix); } @VisibleForTesting  CacheManager(); void setEncoder(@NonNull RevObjectSerializer encoder); ObjectCache acquire(final @NonNull String uniqueCacheIdentifier); void release(ObjectCache cache); @Override long getSize(); @Override long getSizeBytes(); @Override double getSizeMB(); @Override void clear(); @Override long getHitCount(); @Override double getHitRate(); @Override long getMissCount(); @Override double getMissRate(); @Override long getEvictionCount(); @Override void setMaximumSizePercent(double percent); @Override void setMaximumSizeMB(double maxSizeMB); long getMaximumSize(); @Override double getMaximumSizeMB(); @Override void setMaximumSize(long maxSizeBytes); @Override double getMaximumSizePercent(); @Override double getDefaultSizeMB(); @Override double getAbsoluteMaximumSizeMB(); @Nullable @Override String getMaximumSizeSystemProperty(); @Nullable @Override String getMaximumSizeEnvVariable(); @Nullable @Override String getCacheImplementationName(); static final CacheManager INSTANCE; static final String ENV_VAR; }### Answer:
public @Test void acquire() { ObjectCache cache1 = cacheManager.acquire("id1"); assertNotNull(cache1); ObjectCache cache2 = cacheManager.acquire("id1"); assertSame(cache1, cache2); ObjectCache cache3 = cacheManager.acquire("id2"); assertNotNull(cache3); assertNotSame(cache1, cache3); }