Use Block.getGenesis(Network) to reduce use of NetworkParameters

In some classes (CheckpointManager, SPVBlockStore, and MemoryFullPrunedBlockStore) the use of Block.getGenesis() removes the last internal dependency on NetworkParameters and allows the constructor taking NetworkParameters to be replaced with one that takes Network. In FetchBlocks, PrivateKeys, and BlockFileLoaderBitcoindTest NetworkParameters is completely removed. In other classes use of Block.getGenesis() takes us closer to removing NetworkParameters, but there are other uses that must be updated first.
msgilligan · Aug 27, 2026 · Aug 28, 2026 · Jul 30, 2026 · Aug 28, 2026 · c2ad7aefcce9972f050040015f479821e2ab4c2a
commit c2ad7aefcce9972f050040015f479821e2ab4c2a
diff --git a/core/src/main/java/org/bitcoinj/core/CheckpointManager.java b/core/src/main/java/org/bitcoinj/core/CheckpointManager.java
@@ -17,6 +17,7 @@
 package org.bitcoinj.core;
 
 import com.google.common.io.BaseEncoding;
+import org.bitcoinj.base.Network;
 import org.bitcoinj.base.Sha256Hash;
 import org.bitcoinj.base.internal.TimeUtils;
 import org.bitcoinj.store.BlockStore;
@@ -83,7 +84,7 @@ public class CheckpointManager {
     // Map of block header time (in seconds) to data.
     protected final TreeMap<Instant, StoredBlock> checkpoints = new TreeMap<>();
 
-    protected final NetworkParameters params;
+    protected final Network network;
     protected final Sha256Hash dataHash;
 
     /**
@@ -99,7 +100,7 @@ public CheckpointManager(NetworkParameters params) throws IOException {
 
     /** Loads the checkpoints from the given stream */
     public CheckpointManager(NetworkParameters params, @Nullable InputStream inputStream) throws IOException {
-        this.params = Objects.requireNonNull(params);
+        network = Objects.requireNonNull(params).network();
         if (inputStream == null)
             inputStream = openStream(params);
         Objects.requireNonNull(inputStream);
@@ -161,11 +162,11 @@ else if (bytes.length == StoredBlock.COMPACT_SERIALIZED_SIZE_V2)
      */
     public StoredBlock getCheckpointBefore(Instant time) {
         try {
-            checkArgument(time.isAfter(params.getGenesisBlock().time()));
+            checkArgument(time.isAfter(Block.getGenesis(network).time()));
             // This is thread safe because the map never changes after creation.
             Map.Entry<Instant, StoredBlock> entry = checkpoints.floorEntry(time);
             if (entry != null) return entry.getValue();
-            Block genesis = params.getGenesisBlock().asHeader();
+            Block genesis = Block.getGenesis(network).asHeader();
             return new StoredBlock(genesis, genesis.getWork(), 0);
         } catch (VerificationException e) {
             throw new RuntimeException(e);  // Cannot happen.

diff --git a/core/src/main/java/org/bitcoinj/store/SPVBlockStore.java b/core/src/main/java/org/bitcoinj/store/SPVBlockStore.java
@@ -16,6 +16,7 @@
 
 package org.bitcoinj.store;
 
+import org.bitcoinj.base.Network;
 import org.bitcoinj.base.internal.ByteUtils;
 import org.bitcoinj.core.Block;
 import org.bitcoinj.core.NetworkParameters;
@@ -65,7 +66,7 @@ public class SPVBlockStore implements BlockStore {
     static final byte[] HEADER_MAGIC_V2 = "SPV2".getBytes(StandardCharsets.US_ASCII);
 
     private volatile @Nullable MappedByteBuffer buffer;
-    protected final NetworkParameters params;
+    protected final Network network;
 
     // The entire ring-buffer is mmapped and accessing it should be as fast as accessing regular memory once it's
     // faulted in. Unfortunately, in theory practice and theory are the same. In practice they aren't.
@@ -119,7 +120,7 @@ public SPVBlockStore(NetworkParameters params, File file) throws BlockStoreExcep
      */
     public SPVBlockStore(NetworkParameters params, File file, int capacity, boolean grow) throws BlockStoreException {
         Objects.requireNonNull(file);
-        this.params = Objects.requireNonNull(params);
+        network = Objects.requireNonNull(params).network();
         checkArgument(capacity > 0, () -> "capacity must be positive");
         checkArgument(capacity < 144 * 365 * 10, () -> "capacity must be sane"); // 10 years
 
@@ -157,7 +158,7 @@ public SPVBlockStore(NetworkParameters params, File file, int capacity, boolean
                 randomAccessFile.setLength(fileLength);
                 // Map it into memory read/write. See above comment.
                 buffer = channel.map(FileChannel.MapMode.READ_WRITE, 0, fileLength);
-                initNewStore(params.getGenesisBlock());
+                initNewStore(Block.getGenesis(network));
             }
 
             // Maybe migrate V1 to V2 format.
@@ -436,7 +437,7 @@ public void clear() throws Exception {
                 buffer.put((byte)0);
             }
             // Initialize store again
-            initNewStore(params.getGenesisBlock());
+            initNewStore(Block.getGenesis(network));
         } finally { lock.unlock(); }
     }
 }
diff --git a/examples/src/main/java/org/bitcoinj/examples/FetchBlock.java b/examples/src/main/java/org/bitcoinj/examples/FetchBlock.java
@@ -22,7 +22,6 @@
 import org.bitcoinj.base.Sha256Hash;
 import org.bitcoinj.core.Block;
 import org.bitcoinj.core.BlockChain;
-import org.bitcoinj.core.NetworkParameters;
 import org.bitcoinj.core.Peer;
 import org.bitcoinj.core.PeerAddress;
 import org.bitcoinj.core.PeerGroup;
@@ -64,8 +63,7 @@ public Integer call() throws Exception {
         Objects.requireNonNull(blockHashParam);
         System.out.println("Connecting to node");
         final Network network = BitcoinNetwork.TESTNET;
-        final NetworkParameters params = NetworkParameters.of(network);
-        BlockStore blockStore = new MemoryBlockStore(params.getGenesisBlock());
+        BlockStore blockStore = new MemoryBlockStore(Block.getGenesis(network));
         BlockChain chain = new BlockChain(network, blockStore);
         PeerGroup peerGroup = new PeerGroup(network, chain);
         if (localhost) {

diff --git a/examples/src/main/java/org/bitcoinj/examples/PrivateKeys.java b/examples/src/main/java/org/bitcoinj/examples/PrivateKeys.java
@@ -22,8 +22,8 @@
 import org.bitcoinj.base.BitcoinNetwork;
 import org.bitcoinj.base.Network;
 import org.bitcoinj.base.ScriptType;
+import org.bitcoinj.core.Block;
 import org.bitcoinj.core.BlockChain;
-import org.bitcoinj.core.NetworkParameters;
 import org.bitcoinj.core.PeerAddress;
 import org.bitcoinj.core.PeerGroup;
 import org.bitcoinj.crypto.DumpedPrivateKey;
@@ -46,7 +46,6 @@ public class PrivateKeys {
     public static void main(String[] args) throws Exception {
         // TODO: Assumes main network not testnet. Make it selectable.
         Network network = BitcoinNetwork.MAINNET;
-        NetworkParameters params = NetworkParameters.of(network);
         try {
             // Decode the private key from Satoshis Base58 variant. If 51 characters long then it's from Bitcoins
             // dumpprivkey command and includes a version byte and checksum, or if 52 characters long then it has 
@@ -69,7 +68,7 @@ public static void main(String[] args) throws Exception {
             Address destination = wallet.parseAddress(args[1]);
 
             // Find the transactions that involve those coins.
-            final MemoryBlockStore blockStore = new MemoryBlockStore(params.getGenesisBlock());
+            final MemoryBlockStore blockStore = new MemoryBlockStore(Block.getGenesis(network));
             BlockChain chain = new BlockChain(network, wallet, blockStore);
 
             final PeerGroup peerGroup = new PeerGroup(network, chain);

diff --git a/integration-test/src/test/java/org/bitcoinj/test/bitcoind/BlockFileLoaderBitcoindTest.java b/integration-test/src/test/java/org/bitcoinj/test/bitcoind/BlockFileLoaderBitcoindTest.java
@@ -22,7 +22,6 @@
 import org.bitcoinj.core.Block;
 import org.bitcoinj.core.BlockChain;
 import org.bitcoinj.core.Context;
-import org.bitcoinj.core.NetworkParameters;
 import org.bitcoinj.core.PrunedException;
 import org.bitcoinj.store.BlockStore;
 import org.bitcoinj.store.BlockStoreException;
@@ -66,9 +65,8 @@ public void iterateEntireBitcoindBlockchain() {
     @Test
     public void iterateEntireBitcoindBlockchainIntoBlockStore() throws BlockStoreException, PrunedException {
         Network network = BitcoinNetwork.MAINNET;
-        NetworkParameters params = NetworkParameters.of(network);
         BlockFileLoader loader = new BlockFileLoader(network, BlockFileLoader.getReferenceClientBlockFileList());
-        BlockStore store = new MemoryBlockStore(params.getGenesisBlock());
+        BlockStore store = new MemoryBlockStore(Block.getGenesis(network));
         AbstractBlockChain chain = new BlockChain(network, store);
 
         long blockCount = 0;

diff --git a/tools/src/main/java/org/bitcoinj/tools/BlockImporter.java b/tools/src/main/java/org/bitcoinj/tools/BlockImporter.java
@@ -56,7 +56,7 @@ public static void main(String[] args) throws BlockStoreException, VerificationE
                 break;
             case "Mem":
                 checkArgument(args.length == 2);
-                store = new MemoryBlockStore(params.getGenesisBlock());
+                store = new MemoryBlockStore(Block.getGenesis(network));
                 break;
             case "SPV":
                 checkArgument(args.length == 3);

diff --git a/tools/src/main/java/org/bitcoinj/tools/BuildCheckpoints.java b/tools/src/main/java/org/bitcoinj/tools/BuildCheckpoints.java
@@ -19,6 +19,7 @@
 
 import org.bitcoinj.base.BitcoinNetwork;
 import org.bitcoinj.base.internal.TimeUtils;
+import org.bitcoinj.core.Block;
 import org.bitcoinj.core.BlockChain;
 import org.bitcoinj.core.CheckpointManager;
 import org.bitcoinj.core.Context;
@@ -116,7 +117,7 @@ public Integer call() throws Exception {
         // node and to save block headers that are on interval boundaries, as long as they are <1 month old.
         final TreeMap<Integer, StoredBlock> checkpoints;
         final File textFile;
-        try (BlockStore store = new MemoryBlockStore(params.getGenesisBlock())) {
+        try (BlockStore store = new MemoryBlockStore(Block.getGenesis(net))) {
             final BlockChain chain = new BlockChain(net, store);
             final PeerGroup peerGroup = new PeerGroup(net, chain);