question: @ 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 if ( id . equals ( ID_ALPHANET ) ) { return AlphaNetParams . get ( ) ; } else { return null ; } }
target:  Returns the network parameters for the given string ID or NULL if not recognized. 