diff --git a/classlib/src/main/java/org/threeten/bp/ZoneOffset.java b/classlib/src/main/java/org/threeten/bp/ZoneOffset.java
index 4b3112723..a3e2c6b9e 100644
--- a/classlib/src/main/java/org/threeten/bp/ZoneOffset.java
+++ b/classlib/src/main/java/org/threeten/bp/ZoneOffset.java
@@ -39,8 +39,8 @@ import java.io.IOException;
 import java.io.InvalidObjectException;
 import java.io.ObjectStreamException;
 import java.io.Serializable;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentMap;
+import java.util.HashMap;
+import java.util.Map;
 
 import org.threeten.bp.jdk8.Jdk8Methods;
 import org.threeten.bp.temporal.ChronoField;
@@ -101,9 +101,9 @@ public final class ZoneOffset
     };
 
     /** Cache of time-zone offset by offset in seconds. */
-    private static final ConcurrentMap<Integer, ZoneOffset> SECONDS_CACHE = new ConcurrentHashMap<Integer, ZoneOffset>(16, 0.75f, 4);
+    private static final Map<Integer, ZoneOffset> SECONDS_CACHE = new HashMap<>();
     /** Cache of time-zone offset by ID. */
-    private static final ConcurrentMap<String, ZoneOffset> ID_CACHE = new ConcurrentHashMap<String, ZoneOffset>(16, 0.75f, 4);
+    private static final Map<String, ZoneOffset> ID_CACHE = new HashMap<>();
 
     /**
      * The number of seconds per hour.
diff --git a/classlib/src/main/java/org/threeten/bp/chrono/Chronology.java b/classlib/src/main/java/org/threeten/bp/chrono/Chronology.java
index c6a62efab..af6c57573 100644
--- a/classlib/src/main/java/org/threeten/bp/chrono/Chronology.java
+++ b/classlib/src/main/java/org/threeten/bp/chrono/Chronology.java
@@ -36,15 +36,13 @@ import java.io.DataOutput;
 import java.io.IOException;
 import java.io.InvalidObjectException;
 import java.io.ObjectStreamException;
-import java.lang.reflect.InvocationTargetException;
-import java.lang.reflect.Method;
+import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.ServiceLoader;
 import java.util.Set;
-import java.util.concurrent.ConcurrentHashMap;
 
 import org.threeten.bp.Clock;
 import org.threeten.bp.DateTimeException;
@@ -153,24 +151,11 @@ public abstract class Chronology implements Comparable<Chronology> {
     /**
      * Map of available calendars by ID.
      */
-    private static final ConcurrentHashMap<String, Chronology> CHRONOS_BY_ID = new ConcurrentHashMap<String, Chronology>();
+    private static final Map<String, Chronology> CHRONOS_BY_ID = new HashMap<>();
     /**
      * Map of available calendars by calendar type.
      */
-    private static final ConcurrentHashMap<String, Chronology> CHRONOS_BY_TYPE = new ConcurrentHashMap<String, Chronology>();
-    /**
-     * Access JDK 7 method if on JDK 7.
-     */
-    private static final Method LOCALE_METHOD;
-    static {
-        Method method = null;
-        try {
-            method = Locale.class.getMethod("getUnicodeLocaleType", String.class);
-        } catch (Throwable ex) {
-            // ignore
-        }
-        LOCALE_METHOD = method;
-    }
+    private static final Map<String, Chronology> CHRONOS_BY_TYPE = new HashMap<>();
 
     //-----------------------------------------------------------------------
     /**
@@ -240,18 +225,7 @@ public abstract class Chronology implements Comparable<Chronology> {
         init();
         Jdk8Methods.requireNonNull(locale, "locale");
         String type = "iso";
-        if (LOCALE_METHOD != null) {
-            // JDK 7: locale.getUnicodeLocaleType("ca");
-            try {
-                type = (String) LOCALE_METHOD.invoke(locale, "ca");
-            } catch (IllegalArgumentException ex) {
-                // ignore
-            } catch (IllegalAccessException ex) {
-                // ignore
-            } catch (InvocationTargetException ex) {
-                // ignore
-            }
-        } else if (locale.equals(JapaneseChronology.LOCALE)) {
+        if (locale.equals(JapaneseChronology.LOCALE)) {
             type = "japanese";
         }
         if (type == null || "iso".equals(type) || "iso8601".equals(type)) {
diff --git a/classlib/src/main/java/org/threeten/bp/chrono/JapaneseEra.java b/classlib/src/main/java/org/threeten/bp/chrono/JapaneseEra.java
index 6c4ef4e1b..76c0290c7 100644
--- a/classlib/src/main/java/org/threeten/bp/chrono/JapaneseEra.java
+++ b/classlib/src/main/java/org/threeten/bp/chrono/JapaneseEra.java
@@ -38,7 +38,6 @@ import java.io.InvalidObjectException;
 import java.io.ObjectStreamException;
 import java.io.Serializable;
 import java.util.Arrays;
-import java.util.concurrent.atomic.AtomicReference;
 
 import org.threeten.bp.DateTimeException;
 import org.threeten.bp.LocalDate;
@@ -106,7 +105,7 @@ public final class JapaneseEra
     private static final long serialVersionUID = 1466499369062886794L;
 
     // array for the singleton JapaneseEra instances
-    private static final AtomicReference<JapaneseEra[]> KNOWN_ERAS;
+    private static JapaneseEra[] KNOWN_ERAS;
 
     static {
         JapaneseEra[] array = new JapaneseEra[5];
@@ -115,7 +114,7 @@ public final class JapaneseEra
         array[2] = SHOWA;
         array[3] = HEISEI;
         array[4] = REIWA;
-        KNOWN_ERAS = new AtomicReference<JapaneseEra[]>(array);
+        KNOWN_ERAS = array;
     }
 
     /**
@@ -177,7 +176,7 @@ public final class JapaneseEra
      * @throws DateTimeException if an additional era has already been registered
      */
     public static JapaneseEra registerEra(LocalDate since, String name) {
-        JapaneseEra[] known = KNOWN_ERAS.get();
+        JapaneseEra[] known = KNOWN_ERAS;
         if (known.length > 5) {
             throw new DateTimeException("Only one additional Japanese era can be added");
         }
@@ -189,9 +188,7 @@ public final class JapaneseEra
         JapaneseEra era = new JapaneseEra(ADDITIONAL_VALUE, since, name);
         JapaneseEra[] newArray = Arrays.copyOf(known, 6);
         newArray[5] = era;
-        if (!KNOWN_ERAS.compareAndSet(known, newArray)) {
-            throw new DateTimeException("Only one additional Japanese era can be added");
-        }
+        KNOWN_ERAS = newArray;
         return era;
     }
 
@@ -207,7 +204,7 @@ public final class JapaneseEra
      * @throws DateTimeException if the value is invalid
      */
     public static JapaneseEra of(int japaneseEra) {
-        JapaneseEra[] known = KNOWN_ERAS.get();
+        JapaneseEra[] known = KNOWN_ERAS;
         if (japaneseEra < MEIJI.eraValue || japaneseEra > known[known.length - 1].eraValue) {
             throw new DateTimeException("japaneseEra is invalid");
         }
@@ -226,7 +223,7 @@ public final class JapaneseEra
      */
     public static JapaneseEra valueOf(String japaneseEra) {
         Jdk8Methods.requireNonNull(japaneseEra, "japaneseEra");
-        JapaneseEra[] known = KNOWN_ERAS.get();
+        JapaneseEra[] known = KNOWN_ERAS;
         for (JapaneseEra era : known) {
             if (japaneseEra.equals(era.name)) {
                 return era;
@@ -247,7 +244,7 @@ public final class JapaneseEra
      * @return an array of JapaneseEras
      */
     public static JapaneseEra[] values() {
-        JapaneseEra[] known = KNOWN_ERAS.get();
+        JapaneseEra[] known = KNOWN_ERAS;
         return Arrays.copyOf(known, known.length);
     }
 
@@ -262,7 +259,7 @@ public final class JapaneseEra
         if (date.isBefore(MEIJI.since)) {
             throw new DateTimeException("Date too early: " + date);
         }
-        JapaneseEra[] known = KNOWN_ERAS.get();
+        JapaneseEra[] known = KNOWN_ERAS;
         for (int i = known.length - 1; i >= 0; i--) {
             JapaneseEra era = known[i];
             if (date.compareTo(era.since) >= 0) {
diff --git a/classlib/src/main/java/org/threeten/bp/format/DateTimeTextProvider.java b/classlib/src/main/java/org/threeten/bp/format/DateTimeTextProvider.java
index 3066611e1..fba6b4fbc 100644
--- a/classlib/src/main/java/org/threeten/bp/format/DateTimeTextProvider.java
+++ b/classlib/src/main/java/org/threeten/bp/format/DateTimeTextProvider.java
@@ -34,7 +34,6 @@ package org.threeten.bp.format;
 import java.util.Iterator;
 import java.util.Locale;
 import java.util.Map.Entry;
-import java.util.concurrent.atomic.AtomicReference;
 
 import org.threeten.bp.temporal.TemporalField;
 
@@ -51,7 +50,7 @@ import org.threeten.bp.temporal.TemporalField;
  */
 public abstract class DateTimeTextProvider {
 
-    private static final AtomicReference<DateTimeTextProvider> MUTABLE_PROVIDER = new AtomicReference<DateTimeTextProvider>();
+    private static DateTimeTextProvider MUTABLE_PROVIDER;
 
     /**
      * Gets the provider.
@@ -72,9 +71,10 @@ public abstract class DateTimeTextProvider {
      * @throws IllegalStateException if initialization has already occurred or another provider has been set
      */
     public static void setInitializer(DateTimeTextProvider provider) {
-        if (!MUTABLE_PROVIDER.compareAndSet(null, provider)) {
+        if (MUTABLE_PROVIDER != null) {
             throw new IllegalStateException("Provider was already set, possibly with a default during initialization");
         }
+        MUTABLE_PROVIDER = provider;
     }
 
     //-----------------------------------------------------------------------
@@ -120,8 +120,8 @@ public abstract class DateTimeTextProvider {
         // initialize the provider
         static DateTimeTextProvider initialize() {
             // Set the default initializer if none has been provided yet
-            MUTABLE_PROVIDER.compareAndSet(null, new SimpleDateTimeTextProvider());
-            return MUTABLE_PROVIDER.get();
+            MUTABLE_PROVIDER = new SimpleDateTimeTextProvider();
+            return MUTABLE_PROVIDER;
         }
     }
 
diff --git a/classlib/src/main/java/org/threeten/bp/format/DecimalStyle.java b/classlib/src/main/java/org/threeten/bp/format/DecimalStyle.java
index 3aec9354c..828a56b7d 100644
--- a/classlib/src/main/java/org/threeten/bp/format/DecimalStyle.java
+++ b/classlib/src/main/java/org/threeten/bp/format/DecimalStyle.java
@@ -33,11 +33,11 @@ package org.threeten.bp.format;
 
 import java.text.DecimalFormatSymbols;
 import java.util.Arrays;
+import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Locale;
+import java.util.Map;
 import java.util.Set;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentMap;
 
 import org.threeten.bp.jdk8.Jdk8Methods;
 
@@ -61,7 +61,7 @@ public final class DecimalStyle {
     /**
      * The cache of symbols instances.
      */
-    private static final ConcurrentMap<Locale, DecimalStyle> CACHE = new ConcurrentHashMap<Locale, DecimalStyle>(16, 0.75f, 2);
+    private static final Map<Locale, DecimalStyle> CACHE = new HashMap<>();
 
     /**
      * The zero digit.
diff --git a/classlib/src/main/java/org/threeten/bp/format/SimpleDateTimeFormatStyleProvider.java b/classlib/src/main/java/org/threeten/bp/format/SimpleDateTimeFormatStyleProvider.java
index 8d3cc16e2..5d3958343 100644
--- a/classlib/src/main/java/org/threeten/bp/format/SimpleDateTimeFormatStyleProvider.java
+++ b/classlib/src/main/java/org/threeten/bp/format/SimpleDateTimeFormatStyleProvider.java
@@ -33,9 +33,9 @@ package org.threeten.bp.format;
 
 import java.text.DateFormat;
 import java.text.SimpleDateFormat;
+import java.util.HashMap;
 import java.util.Locale;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentMap;
+import java.util.Map;
 
 import org.threeten.bp.chrono.Chronology;
 
@@ -51,8 +51,7 @@ final class SimpleDateTimeFormatStyleProvider extends DateTimeFormatStyleProvide
     // TODO: Better implementation based on CLDR
 
     /** Cache of formatters. */
-    private static final ConcurrentMap<String, Object> FORMATTER_CACHE =
-                        new ConcurrentHashMap<String, Object>(16, 0.75f, 2);
+    private static final Map<String, Object> FORMATTER_CACHE = new HashMap<>();
 
     @Override
     public Locale[] getAvailableLocales() {
diff --git a/classlib/src/main/java/org/threeten/bp/format/SimpleDateTimeTextProvider.java b/classlib/src/main/java/org/threeten/bp/format/SimpleDateTimeTextProvider.java
index bc2de2621..52d5cf0f8 100644
--- a/classlib/src/main/java/org/threeten/bp/format/SimpleDateTimeTextProvider.java
+++ b/classlib/src/main/java/org/threeten/bp/format/SimpleDateTimeTextProvider.java
@@ -49,8 +49,6 @@ import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Map.Entry;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentMap;
 
 import org.threeten.bp.temporal.IsoFields;
 import org.threeten.bp.temporal.TemporalField;
@@ -75,8 +73,7 @@ final class SimpleDateTimeTextProvider extends DateTimeTextProvider {
     };
 
     /** Cache. */
-    private final ConcurrentMap<Entry<TemporalField, Locale>, Object> cache =
-            new ConcurrentHashMap<Entry<TemporalField, Locale>, Object>(16, 0.75f, 2);
+    private final Map<Entry<TemporalField, Locale>, Object> cache =  new HashMap<>();
 
     //-----------------------------------------------------------------------
     @Override
diff --git a/classlib/src/main/java/org/threeten/bp/temporal/WeekFields.java b/classlib/src/main/java/org/threeten/bp/temporal/WeekFields.java
index 197b6f082..89143112a 100644
--- a/classlib/src/main/java/org/threeten/bp/temporal/WeekFields.java
+++ b/classlib/src/main/java/org/threeten/bp/temporal/WeekFields.java
@@ -44,6 +44,7 @@ import static org.threeten.bp.temporal.ChronoUnit.YEARS;
 import java.io.InvalidObjectException;
 import java.io.Serializable;
 import java.util.GregorianCalendar;
+import java.util.HashMap;
 import java.util.Locale;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
@@ -127,7 +128,7 @@ public final class WeekFields implements Serializable {
      * The cache of rules by firstDayOfWeek plus minimalDays.
      * Initialized first to be available for definition of ISO, etc.
      */
-    private static final ConcurrentMap<String, WeekFields> CACHE = new ConcurrentHashMap<String, WeekFields>(4, 0.75f, 2);
+    private static final Map<String, WeekFields> CACHE = new HashMap<>();
 
     /**
      * The ISO-8601 definition, where a week starts on Monday and the first week
diff --git a/classlib/src/main/java/org/threeten/bp/zone/StandardZoneRules.java b/classlib/src/main/java/org/threeten/bp/zone/StandardZoneRules.java
index 9f20424d1..e4c661e3c 100644
--- a/classlib/src/main/java/org/threeten/bp/zone/StandardZoneRules.java
+++ b/classlib/src/main/java/org/threeten/bp/zone/StandardZoneRules.java
@@ -38,9 +38,9 @@ import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.List;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentMap;
+import java.util.Map;
 
 import org.threeten.bp.Duration;
 import org.threeten.bp.Instant;
@@ -98,8 +98,7 @@ final class StandardZoneRules extends ZoneRules implements Serializable {
     /**
      * The map of recent transitions.
      */
-    private final ConcurrentMap<Integer, ZoneOffsetTransition[]> lastRulesCache =
-                new ConcurrentHashMap<Integer, ZoneOffsetTransition[]>();
+    private final Map<Integer, ZoneOffsetTransition[]> lastRulesCache =  new HashMap<>();
 
     /**
      * Creates an instance.
diff --git a/classlib/src/main/java/org/threeten/bp/zone/ZoneRulesInitializer.java b/classlib/src/main/java/org/threeten/bp/zone/ZoneRulesInitializer.java
index 11e34b8fa..bc01aa072 100644
--- a/classlib/src/main/java/org/threeten/bp/zone/ZoneRulesInitializer.java
+++ b/classlib/src/main/java/org/threeten/bp/zone/ZoneRulesInitializer.java
@@ -33,8 +33,6 @@ package org.threeten.bp.zone;
 
 import java.util.ServiceConfigurationError;
 import java.util.ServiceLoader;
-import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.concurrent.atomic.AtomicReference;
 
 /**
  * Controls how the time-zone rules are initialized.
@@ -57,8 +55,8 @@ public abstract class ZoneRulesInitializer {
      */
     public static final ZoneRulesInitializer DO_NOTHING = new DoNothingZoneRulesInitializer();
 
-    private static final AtomicBoolean INITIALIZED = new AtomicBoolean(false);
-    private static final AtomicReference<ZoneRulesInitializer> INITIALIZER = new AtomicReference<ZoneRulesInitializer>();
+    private static boolean INITIALIZED;
+    private static ZoneRulesInitializer INITIALIZER;
 
     /**
      * Sets the initializer to use.
@@ -70,23 +68,27 @@ public abstract class ZoneRulesInitializer {
      * @throws IllegalStateException if initialization has already occurred or another initializer has been set
      */
     public static void setInitializer(ZoneRulesInitializer initializer) {
-        if (INITIALIZED.get()) {
+        if (INITIALIZED) {
             throw new IllegalStateException("Already initialized");
         }
-        if (!INITIALIZER.compareAndSet(null, initializer)) {
+        if (INITIALIZER != null) {
             throw new IllegalStateException("Initializer was already set, possibly with a default during initialization");
         }
+        INITIALIZER = initializer;
     }
 
     //-----------------------------------------------------------------------
     // initialize the providers
     static void initialize() {
-        if (INITIALIZED.getAndSet(true)) {
+        if (INITIALIZED) {
             throw new IllegalStateException("Already initialized");
         }
+        INITIALIZED = true;
         // Set the default initializer if none has been provided yet.
-        INITIALIZER.compareAndSet(null, new ServiceLoaderZoneRulesInitializer());
-        INITIALIZER.get().initializeProviders();
+        if (INITIALIZER ==  null) {
+            INITIALIZER = new ServiceLoaderZoneRulesInitializer();
+        }
+        INITIALIZER.initializeProviders();
     }
 
     /**
diff --git a/classlib/src/main/java/org/threeten/bp/zone/ZoneRulesProvider.java b/classlib/src/main/java/org/threeten/bp/zone/ZoneRulesProvider.java
index db95108b1..2eb8a7905 100644
--- a/classlib/src/main/java/org/threeten/bp/zone/ZoneRulesProvider.java
+++ b/classlib/src/main/java/org/threeten/bp/zone/ZoneRulesProvider.java
@@ -31,12 +31,13 @@
  */
 package org.threeten.bp.zone;
 
+import java.util.ArrayList;
 import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
 import java.util.NavigableMap;
 import java.util.Set;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentMap;
-import java.util.concurrent.CopyOnWriteArrayList;
 
 import org.threeten.bp.DateTimeException;
 import org.threeten.bp.ZoneId;
@@ -73,11 +74,11 @@ public abstract class ZoneRulesProvider {
     /**
      * The set of loaded providers.
      */
-    private static final CopyOnWriteArrayList<ZoneRulesProvider> PROVIDERS = new CopyOnWriteArrayList<ZoneRulesProvider>();
+    private static final List<ZoneRulesProvider> PROVIDERS = new ArrayList<>();
     /**
      * The lookup from zone region ID to provider.
      */
-    private static final ConcurrentMap<String, ZoneRulesProvider> ZONES = new ConcurrentHashMap<String, ZoneRulesProvider>(512, 0.75f, 2);
+    private static final Map<String, ZoneRulesProvider> ZONES = new HashMap<>();
     static {
         ZoneRulesInitializer.initialize();
     }