Make lock objects transient.

This let us move away from the current hack (which was never in a Guava _release_) of using a lock of `new Integer(1)` (because we needed something `Serializable` while we figured this all out).

RELNOTES=n/a
PiperOrigin-RevId: 659714359

Author: cpovirk

android/guava/src/com/google/common/base/Suppliers.java

@@ -23,6 +23,8 @@
 import com.google.common.annotations.GwtIncompatible;
 import com.google.common.annotations.J2ktIncompatible;
 import com.google.common.annotations.VisibleForTesting;
+import java.io.IOException;
+import java.io.ObjectInputStream;
 import java.io.Serializable;
 import java.time.Duration;
 import java.util.concurrent.TimeUnit;
@@ -120,8 +122,7 @@ public String toString() {
 
   @VisibleForTesting
   static class MemoizingSupplier<T extends @Nullable Object> implements Supplier<T>, Serializable {
-    private final Object lock =
-        new Integer(1); // something serializable
+    private transient Object lock = new Object();
 
     final Supplier<T> delegate;
     transient volatile boolean initialized;
@@ -135,6 +136,8 @@ static class MemoizingSupplier<T extends @Nullable Object> implements Supplier<T
 
     @Override
     @ParametricNullness
+    // We set the field only once (during construction or deserialization).
+    @SuppressWarnings("SynchronizeOnNonFinalField")
     public T get() {
       // A 2-field variant of Double Checked Locking.
       if (!initialized) {
@@ -158,6 +161,13 @@ public String toString() {
           + ")";
     }
 
+    @GwtIncompatible // serialization
+    @J2ktIncompatible // serialization
+    private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
+      in.defaultReadObject();
+      lock = new Object();
+    }
+
     private static final long serialVersionUID = 0;
   }
 
@@ -275,8 +285,7 @@ public String toString() {
   @SuppressWarnings("GoodTime") // lots of violations
   static class ExpiringMemoizingSupplier<T extends @Nullable Object>
       implements Supplier<T>, Serializable {
-    private final Object lock =
-        new Integer(1); // something serializable
+    private transient Object lock = new Object();
 
     final Supplier<T> delegate;
     final long durationNanos;
@@ -291,6 +300,8 @@ static class ExpiringMemoizingSupplier<T extends @Nullable Object>
 
     @Override
     @ParametricNullness
+    // We set the field only once (during construction or deserialization).
+    @SuppressWarnings("SynchronizeOnNonFinalField")
     public T get() {
       // Another variant of Double Checked Locking.
       //
@@ -324,6 +335,13 @@ public String toString() {
       return "Suppliers.memoizeWithExpiration(" + delegate + ", " + durationNanos + ", NANOS)";
     }
 
+    @GwtIncompatible // serialization
+    @J2ktIncompatible // serialization
+    private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
+      in.defaultReadObject();
+      lock = new Object();
+    }
+
     private static final long serialVersionUID = 0;
   }
 

guava/src/com/google/common/base/Suppliers.java

@@ -23,6 +23,8 @@
 import com.google.common.annotations.GwtIncompatible;
 import com.google.common.annotations.J2ktIncompatible;
 import com.google.common.annotations.VisibleForTesting;
+import java.io.IOException;
+import java.io.ObjectInputStream;
 import java.io.Serializable;
 import java.time.Duration;
 import java.util.concurrent.TimeUnit;
@@ -120,8 +122,7 @@ public String toString() {
 
   @VisibleForTesting
   static class MemoizingSupplier<T extends @Nullable Object> implements Supplier<T>, Serializable {
-    private final Object lock =
-        new Integer(1); // something serializable
+    private transient Object lock = new Object();
 
     final Supplier<T> delegate;
     transient volatile boolean initialized;
@@ -135,6 +136,8 @@ static class MemoizingSupplier<T extends @Nullable Object> implements Supplier<T
 
     @Override
     @ParametricNullness
+    // We set the field only once (during construction or deserialization).
+    @SuppressWarnings("SynchronizeOnNonFinalField")
     public T get() {
       // A 2-field variant of Double Checked Locking.
       if (!initialized) {
@@ -158,6 +161,13 @@ public String toString() {
           + ")";
     }
 
+    @GwtIncompatible // serialization
+    @J2ktIncompatible // serialization
+    private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
+      in.defaultReadObject();
+      lock = new Object();
+    }
+
     private static final long serialVersionUID = 0;
   }
 
@@ -275,8 +285,7 @@ public String toString() {
   @SuppressWarnings("GoodTime") // lots of violations
   static class ExpiringMemoizingSupplier<T extends @Nullable Object>
       implements Supplier<T>, Serializable {
-    private final Object lock =
-        new Integer(1); // something serializable
+    private transient Object lock = new Object();
 
     final Supplier<T> delegate;
     final long durationNanos;
@@ -291,6 +300,8 @@ static class ExpiringMemoizingSupplier<T extends @Nullable Object>
 
     @Override
     @ParametricNullness
+    // We set the field only once (during construction or deserialization).
+    @SuppressWarnings("SynchronizeOnNonFinalField")
     public T get() {
       // Another variant of Double Checked Locking.
       //
@@ -324,6 +335,13 @@ public String toString() {
       return "Suppliers.memoizeWithExpiration(" + delegate + ", " + durationNanos + ", NANOS)";
     }
 
+    @GwtIncompatible // serialization
+    @J2ktIncompatible // serialization
+    private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
+      in.defaultReadObject();
+      lock = new Object();
+    }
+
     private static final long serialVersionUID = 0;
   }