From 8deb113a5e1af96b01e5e01a8f00d39761201e07 Mon Sep 17 00:00:00 2001
From: Sean Gilligan <sean@msgilligan.com>
Date: Tue, 26 May 2020 13:19:07 -0700
Subject: [PATCH] Networks: Replace usage of Guava ImmutableSet with
 Collections.unmodifiableSet().

---
 .../java/org/bitcoinj/params/Networks.java    | 45 +++++++++++--------
 1 file changed, 27 insertions(+), 18 deletions(-)

diff --git a/core/src/main/java/org/bitcoinj/params/Networks.java b/core/src/main/java/org/bitcoinj/params/Networks.java
index dd33fcac0..fc6b429fd 100644
--- a/core/src/main/java/org/bitcoinj/params/Networks.java
+++ b/core/src/main/java/org/bitcoinj/params/Networks.java
@@ -17,10 +17,11 @@
 package org.bitcoinj.params;
 
 import org.bitcoinj.core.NetworkParameters;
-import com.google.common.collect.ImmutableSet;
-import com.google.common.collect.Lists;
 
+import java.util.Arrays;
 import java.util.Collection;
+import java.util.Collections;
+import java.util.HashSet;
 import java.util.Set;
 
 /**
@@ -32,7 +33,7 @@ import java.util.Set;
  */
 public class Networks {
     /** Registered networks */
-    private static Set<NetworkParameters> networks = ImmutableSet.<NetworkParameters>of(TestNet3Params.get(), MainNetParams.get());
+    private static Set<NetworkParameters> networks = unmodifiableSet(TestNet3Params.get(), MainNetParams.get());
 
     public static Set<NetworkParameters> get() {
         return networks;
@@ -44,7 +45,7 @@ public class Networks {
      * @param network Network to register/add.
      */
     public static void register(NetworkParameters network) {
-        register(Lists.newArrayList(network));
+        register(Collections.singleton(network));
     }
 
     /**
@@ -53,11 +54,8 @@ public class Networks {
      *
      * @param networks Networks to register/add.
      */
-    public static void register(Collection<? extends NetworkParameters> networks) {
-        ImmutableSet.Builder<NetworkParameters> builder = ImmutableSet.builder();
-        builder.addAll(Networks.networks);
-        builder.addAll(networks);
-        Networks.networks = builder.build();
+    public static void register(Collection<NetworkParameters> networks) {
+        Networks.networks = combinedSet(Networks.networks, networks);
     }
 
     /**
@@ -66,14 +64,25 @@ public class Networks {
      * @param network Network type to unregister/remove.
      */
     public static void unregister(NetworkParameters network) {
-        if (networks.contains(network)) {
-            ImmutableSet.Builder<NetworkParameters> builder = ImmutableSet.builder();
-            for (NetworkParameters parameters : networks) {
-                if (parameters.equals(network))
-                    continue;
-                builder.add(parameters);
-            }
-            networks = builder.build();
-        }
+        Networks.networks = removeFromSet(networks, network);
+    }
+
+    // Create an unmodifiable set of NetworkParameters from an array/varargs
+    private static Set<NetworkParameters> unmodifiableSet(NetworkParameters... ts) {
+        return Collections.unmodifiableSet(new HashSet<>(Arrays.asList(ts)));
+    }
+
+    // Create an unmodifiable set by combining two collections
+    private static <T> Set<T> combinedSet(Collection<T> a, Collection<T> b) {
+        Set<T> tempSet = new HashSet<>(a);
+        tempSet.addAll(b);
+        return Collections.unmodifiableSet(tempSet);
+    }
+
+    // Create a new unmodifiable set by removing an item from an existing set
+    private static <T> Set<T> removeFromSet(Set<T> set, T item) {
+        Set<T> tempSet = new HashSet<>(set);
+        tempSet.remove(item);
+        return Collections.unmodifiableSet(tempSet);
     }
 }