Use Guava Stopwatch for measuring code execution time.

core/src/main/java/org/bitcoinj/core/PeerGroup.java

@@ -880,7 +880,7 @@ protected int discoverPeers() throws PeerDiscoveryException {
         checkState(!lock.isHeldByCurrentThread());
         int maxPeersToDiscoverCount = this.vMaxPeersToDiscoverCount;
         long peerDiscoveryTimeoutMillis = this.vPeerDiscoveryTimeoutMillis;
-        long start = System.currentTimeMillis();
+        final Stopwatch watch = Stopwatch.createStarted();
         final List<PeerAddress> addressList = Lists.newLinkedList();
         for (PeerDiscovery peerDiscovery : peerDiscoverers /* COW */) {
             InetSocketAddress[] addresses;
@@ -902,8 +902,8 @@ public void run() {
                 });
             }
         }
-        log.info("Peer discovery took {}ms and returned {} items", System.currentTimeMillis() - start,
-                addressList.size());
+        watch.stop();
+        log.info("Peer discovery took {} and returned {} items", watch, addressList.size());
         return addressList.size();
     }
 

core/src/main/java/org/bitcoinj/crypto/MnemonicCode.java

@@ -22,6 +22,8 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import com.google.common.base.Stopwatch;
+
 import java.io.BufferedReader;
 import java.io.FileNotFoundException;
 import java.io.IOException;
@@ -128,9 +130,10 @@ public static byte[] toSeed(List<String> words, String passphrase) {
         String pass = Utils.join(words);
         String salt = "mnemonic" + passphrase;
 
-        long start = System.currentTimeMillis();
+        final Stopwatch watch = Stopwatch.createStarted();
         byte[] seed = PBKDF2SHA512.derive(pass, salt, PBKDF2_ROUNDS, 64);
-        log.info("PBKDF2 took {}ms", System.currentTimeMillis() - start);
+        watch.stop();
+        log.info("PBKDF2 took {}", watch);
         return seed;
     }
 

core/src/main/java/org/bitcoinj/params/AbstractBitcoinNetParams.java

@@ -18,6 +18,7 @@
 package org.bitcoinj.params;
 
 import java.math.BigInteger;
+import java.util.concurrent.TimeUnit;
 
 import org.bitcoinj.core.Block;
 import org.bitcoinj.core.Coin;
@@ -32,6 +33,8 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import com.google.common.base.Stopwatch;
+
 import org.bitcoinj.core.BitcoinSerializer;
 
 /**
@@ -76,7 +79,7 @@ public void checkDifficultyTransitions(final StoredBlock storedPrev, final Block
 
         // We need to find a block far back in the chain. It's OK that this is expensive because it only occurs every
         // two weeks after the initial block chain download.
-        long now = System.currentTimeMillis();
+        final Stopwatch watch = Stopwatch.createStarted();
         StoredBlock cursor = blockStore.get(prev.getHash());
         for (int i = 0; i < this.getInterval() - 1; i++) {
             if (cursor == null) {
@@ -86,9 +89,9 @@ public void checkDifficultyTransitions(final StoredBlock storedPrev, final Block
             }
             cursor = blockStore.get(cursor.getHeader().getPrevBlockHash());
         }
-        long elapsed = System.currentTimeMillis() - now;
-        if (elapsed > 50)
-            log.info("Difficulty transition traversal took {}msec", elapsed);
+        watch.stop();
+        if (watch.elapsed(TimeUnit.MILLISECONDS) > 50)
+            log.info("Difficulty transition traversal took {}", watch);
 
         Block blockIntervalAgo = cursor.getHeader();
         int timespan = (int) (prev.getTimeSeconds() - blockIntervalAgo.getTimeSeconds());

core/src/main/java/org/bitcoinj/wallet/DeterministicKeyChain.java

@@ -1,5 +1,6 @@
 /**
  * Copyright 2014 The bitcoinj developers.
+ * Copyright 2015 Andreas Schildbach
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,6 +26,7 @@
 import org.bitcoinj.store.UnreadableWalletException;
 import org.bitcoinj.utils.Threading;
 
+import com.google.common.base.Stopwatch;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterators;
 import com.google.common.collect.PeekingIterator;
@@ -1173,7 +1175,7 @@ private List<DeterministicKey> maybeLookAhead(DeterministicKey parent, int issue
                 needed, parent.getPathAsString(), issued, lookaheadSize, lookaheadThreshold, numChildren);
 
         List<DeterministicKey> result  = new ArrayList<DeterministicKey>(needed);
-        long now = System.currentTimeMillis();
+        final Stopwatch watch = Stopwatch.createStarted();
         int nextChild = numChildren;
         for (int i = 0; i < needed; i++) {
             DeterministicKey key = HDKeyDerivation.deriveThisOrNextChildKey(parent, nextChild);
@@ -1182,7 +1184,8 @@ private List<DeterministicKey> maybeLookAhead(DeterministicKey parent, int issue
             result.add(key);
             nextChild = key.getChildNumber().num() + 1;
         }
-        log.info("Took {} msec", System.currentTimeMillis() - now);
+        watch.stop();
+        log.info("Took {}", watch);
         return result;
     }
 

core/src/main/java/org/bitcoinj/wallet/WalletFiles.java

@@ -21,6 +21,8 @@
 import org.bitcoinj.utils.*;
 import org.slf4j.*;
 
+import com.google.common.base.Stopwatch;
+
 import javax.annotation.*;
 import java.io.*;
 import java.util.concurrent.*;
@@ -106,7 +108,7 @@ public void saveNow() throws IOException {
     }
 
     private void saveNowInternal() throws IOException {
-        long now = System.currentTimeMillis();
+        final Stopwatch watch = Stopwatch.createStarted();
         File directory = file.getAbsoluteFile().getParentFile();
         File temp = File.createTempFile("wallet", null, directory);
         final Listener listener = vListener;
@@ -115,7 +117,8 @@ private void saveNowInternal() throws IOException {
         wallet.saveToFile(temp, file);
         if (listener != null)
             listener.onAfterAutoSave(file);
-        log.info("Save completed in {}msec", System.currentTimeMillis() - now);
+        watch.stop();
+        log.info("Save completed in {}", watch);
     }
 
     /** Queues up a save in the background. Useful for not very important wallet changes. */

core/src/test/java/org/bitcoinj/core/PeerGroupTest.java

@@ -17,6 +17,7 @@
 
 package org.bitcoinj.core;
 
+import com.google.common.base.Stopwatch;
 import com.google.common.collect.*;
 import com.google.common.net.*;
 import com.google.common.util.concurrent.*;
@@ -507,7 +508,7 @@ public void onPeerDisconnected(Peer peer, int peerCount) {
             }
         });
         // connect to peer but don't do handshake
-        long start = System.currentTimeMillis(); // before connection so we don't get elapsed < timeout
+        final Stopwatch watch = Stopwatch.createStarted(); // before connection so we don't get elapsed < timeout
         connectPeerWithoutVersionExchange(0);
         // wait for disconnect (plus a bit more, in case test server is overloaded)
         try {
@@ -516,9 +517,9 @@ public void onPeerDisconnected(Peer peer, int peerCount) {
             // the checks below suffice for this case too
         }
         // check things after disconnect
-        long end = System.currentTimeMillis();
+        watch.stop();
         assertFalse(peerConnectedFuture.isDone()); // should never have connected
-        assertTrue(end - start >= timeout); // should not disconnect before timeout
+        assertTrue(watch.elapsed(TimeUnit.MILLISECONDS) >= timeout); // should not disconnect before timeout
         assertTrue(peerDisconnectedFuture.isDone()); // but should disconnect eventually
     }