/** Returns the network parameters for the given string ID or NULL if not recognized. */
 @Nullable
 public static NetworkParameters fromID(String id) {
   if (id.equals(ID_MAINNET)) {
     return MainNetParams.get();
   } else if (id.equals(ID_TESTNET)) {
     return TestNet3Params.get();
   } else if (id.equals(ID_UNITTESTNET)) {
     return UnitTestParams.get();
   } else if (id.equals(ID_REGTEST)) {
     return RegTestParams.get();
   } else {
     return null;
   }
 }
 /** Returns a testnet params modified to allow any difficulty target. */
 @Deprecated
 public static NetworkParameters unitTests() {
   return UnitTestParams.get();
 }