Extract ID generation methods to new public IdUtils class

epoxy-adapter/src/main/java/com/airbnb/epoxy/EpoxyModel.java

@@ -15,6 +15,9 @@
 import androidx.annotation.Nullable;
 import androidx.annotation.Px;
 
+import static com.airbnb.epoxy.IdUtils.hashLong64Bit;
+import static com.airbnb.epoxy.IdUtils.hashString64Bit;
+
 /**
  * Helper to bind data to a view using a builder style. The parameterized type should extend
  * Android's View.
@@ -237,7 +240,7 @@ public EpoxyModel<T> id(long id1, long id2) {
    * several hundred models in the adapter, there would be roughly 1 in 100 trillion chance of a
    * collision. (http://preshing.com/20110504/hash-collision-probabilities/)
    *
-   * @see EpoxyModel#hashString64Bit(CharSequence)
+   * @see IdUtils#hashString64Bit(CharSequence)
    */
   public EpoxyModel<T> id(@Nullable CharSequence key) {
     id(hashString64Bit(key));
@@ -268,8 +271,8 @@ public EpoxyModel<T> id(@Nullable CharSequence key, @Nullable CharSequence... ot
    * several hundred models in the adapter, there would be roughly 1 in 100 trillion chance of a
    * collision. (http://preshing.com/20110504/hash-collision-probabilities/)
    *
-   * @see EpoxyModel#hashString64Bit(CharSequence)
-   * @see EpoxyModel#hashLong64Bit(long)
+   * @see IdUtils#hashString64Bit(CharSequence)
+   * @see IdUtils#hashLong64Bit(long)
    */
   public EpoxyModel<T> id(@Nullable CharSequence key, long id) {
     long result = hashString64Bit(key);
@@ -278,44 +281,6 @@ public EpoxyModel<T> id(@Nullable CharSequence key, long id) {
     return this;
   }
 
-  /**
-   * Hash a long into 64 bits instead of the normal 32. This uses a xor shift implementation to
-   * attempt psuedo randomness so object ids have an even spread for less chance of collisions.
-   * <p>
-   * From http://stackoverflow.com/a/11554034
-   * <p>
-   * http://www.javamex.com/tutorials/random_numbers/xorshift.shtml
-   */
-  private static long hashLong64Bit(long value) {
-    value ^= (value << 21);
-    value ^= (value >>> 35);
-    value ^= (value << 4);
-    return value;
-  }
-
-  /**
-   * Hash a string into 64 bits instead of the normal 32. This allows us to better use strings as a
-   * model id with less chance of collisions. This uses the FNV-1a algorithm for a good mix of speed
-   * and distribution.
-   * <p>
-   * Performance comparisons found at http://stackoverflow.com/a/1660613
-   * <p>
-   * Hash implementation from http://www.isthe.com/chongo/tech/comp/fnv/index.html#FNV-1a
-   */
-  private static long hashString64Bit(@Nullable CharSequence str) {
-    if (str == null) {
-      return 0;
-    }
-
-    long result = 0xcbf29ce484222325L;
-    final int len = str.length();
-    for (int i = 0; i < len; i++) {
-      result ^= str.charAt(i);
-      result *= 0x100000001b3L;
-    }
-    return result;
-  }
-
   /**
    * Return the default layout resource to be used when creating views for this model. The resource
    * will be inflated to create a view for the model; additionally the layout int is used as the

epoxy-adapter/src/main/java/com/airbnb/epoxy/IdUtils.java

@@ -0,0 +1,49 @@
+package com.airbnb.epoxy;
+
+import androidx.annotation.Nullable;
+
+/**
+ * Utilities for generating 64-bit long IDs from types such as {@link CharSequence}.
+ */
+public final class IdUtils {
+  private IdUtils() {
+  }
+
+  /**
+   * Hash a long into 64 bits instead of the normal 32. This uses a xor shift implementation to
+   * attempt psuedo randomness so object ids have an even spread for less chance of collisions.
+   * <p>
+   * From http://stackoverflow.com/a/11554034
+   * <p>
+   * http://www.javamex.com/tutorials/random_numbers/xorshift.shtml
+   */
+  public static long hashLong64Bit(long value) {
+    value ^= (value << 21);
+    value ^= (value >>> 35);
+    value ^= (value << 4);
+    return value;
+  }
+
+  /**
+   * Hash a string into 64 bits instead of the normal 32. This allows us to better use strings as a
+   * model id with less chance of collisions. This uses the FNV-1a algorithm for a good mix of speed
+   * and distribution.
+   * <p>
+   * Performance comparisons found at http://stackoverflow.com/a/1660613
+   * <p>
+   * Hash implementation from http://www.isthe.com/chongo/tech/comp/fnv/index.html#FNV-1a
+   */
+  public static long hashString64Bit(@Nullable CharSequence str) {
+    if (str == null) {
+      return 0;
+    }
+
+    long result = 0xcbf29ce484222325L;
+    final int len = str.length();
+    for (int i = 0; i < len; i++) {
+      result ^= str.charAt(i);
+      result *= 0x100000001b3L;
+    }
+    return result;
+  }
+}