solve sonar problem

Author: zeusoo001

chainbase/src/main/java/org/tron/core/store/AccountStore.java

@@ -24,6 +24,8 @@
 @Component
 public class AccountStore extends TronStoreWithRevoking<AccountCapsule> {
 
+  private static String ACCOUNT_BLACKHOLE = "Blackhole";
+
   private static Map<String, byte[]> assertsAddress = new HashMap<>(); // key = name , value = address
 
   @Autowired
@@ -51,7 +53,7 @@ public static void setAccount(com.typesafe.config.Config config) {
       byte[] address = Commons.decodeFromBase58Check(obj.get("address").unwrapped().toString());
       assertsAddress.put(accountName, address);
     }
-    if (assertsAddress.get("Blackhole") == null) {
+    if (assertsAddress.get(ACCOUNT_BLACKHOLE) == null) {
       throw new TronError("Account[Blackhole] is not configured.", TronError.ErrCode.GENESIS_BLOCK_INIT);
     }
   }
@@ -113,12 +115,12 @@ public AccountCapsule getSun() {
    * Min TRX account.
    */
   public AccountCapsule getBlackhole() {
-    return getUnchecked(assertsAddress.get("Blackhole"));
+    return getUnchecked(assertsAddress.get(ACCOUNT_BLACKHOLE));
   }
 
 
   public byte[] getBlackholeAddress() {
-    return assertsAddress.get("Blackhole");
+    return assertsAddress.get(ACCOUNT_BLACKHOLE);
   }
 
   /**