How does JAVA use redisUtils utility classes to prevent concurrency problems in highly concurrent access caches?

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Import lombok.extern.slf4j.Slf4j;import org.springframework.data.redis.core.BoundHashOperations;import org.springframework.data.redis.core.BoundValueOperations;import org.springframework.data.redis.core.RedisTemplate;import org.springframework.data.redis.core.StringRedisTemplate;import java.util.Map;import java.util.concurrent.TimeUnit;import java.util.function.BiFunction;import java.util.function.Function @ Slf4jpublic class RedisUtils {/ * @ param redisTemplate redis operation template tool * @ param key cache primary key * @ param timeout expiration time * @ param timeUnit expiration time unit * @ return * @ description method description * @ author kejie.huang * @ date 9:20 on 2019-10-18 * / public static void expire (RedisTemplate redisTemplate, String key Long timeout, TimeUnit timeUnit) {boolean hasKey = redisTemplate.hasKey (key) / / if key exists if (hasKey) {/ / sets Long timeOut = redisTemplate.getExpire (key) if the expiration time is permanent; if (timeOut.intValue () = =-1) {redisTemplate.expire (key, timeout, timeUnit) } public static Object getValue (RedisTemplate redisTemplate, String key, Function mappingFunction) {BoundValueOperations boundValueOperations = redisTemplate.boundValueOps (key); Object value = boundValueOperations.get (); if (value = = null) {synchronized (key.intern ()) {value = boundValueOperations.get () If (value = = null) {value = mappingFunction.apply (key); if (value! = null) {boundValueOperations.set (value);} return value } public static Object getHashValue (RedisTemplate redisTemplate, String key, String hashKey, BiFunction mappingFunction) {BoundHashOperations boundHashOperations = redisTemplate.boundHashOps (key); Object value = boundHashOperations.get (hashKey); if (value = = null) {synchronized (key.concat (hashKey). Intern ()) {value = boundHashOperations.get (hashKey) If (value = = null) {value = mappingFunction.apply (key, hashKey); if (value! = null) {boundHashOperations.put (hashKey, value);} return value;} public static Map getHashValue (RedisTemplate redisTemplate, String key, Function)