Payments.

Co-authored-by: Alan Evans <alan@signal.org>
Co-authored-by: Alex Hart <alex@signal.org>
Co-authored-by: Cody Henthorne <cody@signal.org>

core-util/src/main/java/org/signal/core/util/MapUtil.java

@@ -0,0 +1,23 @@
+package org.signal.core.util;
+
+import android.os.Build;
+
+import androidx.annotation.NonNull;
+
+import java.util.Map;
+
+public final class MapUtil {
+
+  private MapUtil() {}
+
+  @NonNull
+  public static <K, V> V getOrDefault(@NonNull Map<K, V> map, @NonNull K key, @NonNull V defaultValue) {
+    if (Build.VERSION.SDK_INT >= 24) {
+      //noinspection ConstantConditions
+      return map.getOrDefault(key, defaultValue);
+    } else {
+      V v = map.get(key);
+      return v == null ? defaultValue : v;
+    }
+  }
+}