(feat) MemoizingSupplier.isMemoized

google · Jan 8, 2025 · 56ac6ff · 56ac6ff
1 parent d1a3cd5
commit 56ac6ff
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Showing 4 changed files with 86 additions and 30 deletions.
diff --git a/android/guava-tests/test/com/google/common/base/SuppliersTest.java b/android/guava-tests/test/com/google/common/base/SuppliersTest.java
@@ -81,15 +81,16 @@ static class SerializableThrowingSupplier extends ThrowingSupplier implements Se
     private static final long serialVersionUID = 0L;
   }
 
-  static void checkMemoize(CountingSupplier countingSupplier, Supplier<Integer> memoizedSupplier) {
+  static void checkMemoize(CountingSupplier countingSupplier,
+      Suppliers.MemoizingSupplier<Integer> memoizedSupplier) {
     // the underlying supplier hasn't executed yet
     assertEquals(0, countingSupplier.calls);
-
+    assertFalse(memoizedSupplier.isMemoized());
     assertEquals(10, (int) memoizedSupplier.get());
 
     // now it has
     assertEquals(1, countingSupplier.calls);
-
+    assertTrue(memoizedSupplier.isMemoized());
     assertEquals(10, (int) memoizedSupplier.get());
 
     // it still should only have executed once due to memoization
@@ -102,7 +103,7 @@ public void testMemoize() {
   }
 
   private void memoizeTest(CountingSupplier countingSupplier) {
-    Supplier<Integer> memoizedSupplier = Suppliers.memoize(countingSupplier);
+    Suppliers.MemoizingSupplier<Integer> memoizedSupplier = Suppliers.memoize(countingSupplier);
     checkMemoize(countingSupplier, memoizedSupplier);
   }
 
@@ -139,7 +140,7 @@ private void memoizeExceptionThrownTest(ThrowingSupplier throwingSupplier) {
   @GwtIncompatible // SerializableTester
   public void testMemoizeNonSerializable() throws Exception {
     CountingSupplier countingSupplier = new CountingSupplier();
-    Supplier<Integer> memoizedSupplier = Suppliers.memoize(countingSupplier);
+    Suppliers.MemoizingSupplier<Integer> memoizedSupplier = Suppliers.memoize(countingSupplier);
     assertThat(memoizedSupplier.toString()).isEqualTo("Suppliers.memoize(CountingSupplier)");
     checkMemoize(countingSupplier, memoizedSupplier);
     // Calls to the original memoized supplier shouldn't affect its copy.
@@ -156,19 +157,19 @@ public void testMemoizeNonSerializable() throws Exception {
   @GwtIncompatible // SerializableTester
   public void testMemoizeSerializable() throws Exception {
     SerializableCountingSupplier countingSupplier = new SerializableCountingSupplier();
-    Supplier<Integer> memoizedSupplier = Suppliers.memoize(countingSupplier);
+    Suppliers.MemoizingSupplier<Integer> memoizedSupplier = Suppliers.memoize(countingSupplier);
     assertThat(memoizedSupplier.toString()).isEqualTo("Suppliers.memoize(CountingSupplier)");
     checkMemoize(countingSupplier, memoizedSupplier);
     // Calls to the original memoized supplier shouldn't affect its copy.
     Object unused = memoizedSupplier.get();
     assertThat(memoizedSupplier.toString())
         .isEqualTo("Suppliers.memoize(<supplier that returned 10>)");
 
-    Supplier<Integer> copy = reserialize(memoizedSupplier);
+    Suppliers.MemoizingSupplier<Integer> copy = reserialize(memoizedSupplier);
     Object unused2 = memoizedSupplier.get();
 
     CountingSupplier countingCopy =
-        (CountingSupplier) ((Suppliers.MemoizingSupplier<Integer>) copy).delegate;
+        (CountingSupplier) ((Suppliers.SerializableMemoizingSupplier<Integer>) copy).delegate;
     checkMemoize(countingCopy, copy);
   }
 

diff --git a/android/guava/src/com/google/common/base/Suppliers.java b/android/guava/src/com/google/common/base/Suppliers.java
@@ -108,18 +108,34 @@ public String toString() {
    * <p>If {@code delegate} is an instance created by an earlier call to {@code memoize}, it is
    * returned directly.
    */
-  public static <T extends @Nullable Object> Supplier<T> memoize(Supplier<T> delegate) {
+  public static <T extends @Nullable Object> MemoizingSupplier<T> memoize(Supplier<T> delegate) {
     if (delegate instanceof NonSerializableMemoizingSupplier
-        || delegate instanceof MemoizingSupplier) {
-      return delegate;
+        || delegate instanceof SerializableMemoizingSupplier) {
+      return (MemoizingSupplier<T>) delegate;
     }
     return delegate instanceof Serializable
-        ? new MemoizingSupplier<T>(delegate)
+        ? new SerializableMemoizingSupplier<T>(delegate)
         : new NonSerializableMemoizingSupplier<T>(delegate);
   }
 
+  /**
+   * A supplier that memoizes the result of the first call to {@link #get()} and returns the same
+   * result on subsequent calls to {@link #get()}.
+   *
+   * @author Alexey Pelykh
+   */
+  @ElementTypesAreNonnullByDefault
+  public interface MemoizingSupplier<T extends @Nullable Object> extends Supplier<T> {
+    /**
+     * Returns {@code true} if the supplier has been initialized, i.e. if the first call to
+     * {@link #get()} has been made or if the supplier has been explicitly initialized.
+     */
+    boolean isMemoized();
+  }
+
   @VisibleForTesting
-  static class MemoizingSupplier<T extends @Nullable Object> implements Supplier<T>, Serializable {
+  static class SerializableMemoizingSupplier<T extends @Nullable Object>
+      implements MemoizingSupplier<T>, Serializable {
     private transient Object lock = new Object();
 
     final Supplier<T> delegate;
@@ -128,7 +144,7 @@ static class MemoizingSupplier<T extends @Nullable Object> implements Supplier<T
     // on volatile read of "initialized".
     transient @Nullable T value;
 
-    MemoizingSupplier(Supplier<T> delegate) {
+    SerializableMemoizingSupplier(Supplier<T> delegate) {
       this.delegate = checkNotNull(delegate);
     }
 
@@ -152,6 +168,11 @@ public T get() {
       return uncheckedCastNullableTToT(value);
     }
 
+    @Override
+    public boolean isMemoized() {
+      return initialized;
+    }
+
     @Override
     public String toString() {
       return "Suppliers.memoize("
@@ -170,7 +191,8 @@ private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundE
   }
 
   @VisibleForTesting
-  static class NonSerializableMemoizingSupplier<T extends @Nullable Object> implements Supplier<T> {
+  static class NonSerializableMemoizingSupplier<T extends @Nullable Object>
+      implements MemoizingSupplier<T> {
     private final Object lock = new Object();
 
     @SuppressWarnings("UnnecessaryLambda") // Must be a fixed singleton object
@@ -206,6 +228,11 @@ public T get() {
       return uncheckedCastNullableTToT(value);
     }
 
+    @Override
+    public boolean isMemoized() {
+      return delegate == SUCCESSFULLY_COMPUTED;
+    }
+
     @Override
     public String toString() {
       Supplier<T> delegate = this.delegate;

diff --git a/guava-tests/test/com/google/common/base/SuppliersTest.java b/guava-tests/test/com/google/common/base/SuppliersTest.java
@@ -81,15 +81,16 @@ static class SerializableThrowingSupplier extends ThrowingSupplier implements Se
     private static final long serialVersionUID = 0L;
   }
 
-  static void checkMemoize(CountingSupplier countingSupplier, Supplier<Integer> memoizedSupplier) {
+  static void checkMemoize(CountingSupplier countingSupplier,
+      Suppliers.MemoizingSupplier<Integer> memoizedSupplier) {
     // the underlying supplier hasn't executed yet
     assertEquals(0, countingSupplier.calls);
-
+    assertFalse(memoizedSupplier.isMemoized());
     assertEquals(10, (int) memoizedSupplier.get());
 
     // now it has
     assertEquals(1, countingSupplier.calls);
-
+    assertTrue(memoizedSupplier.isMemoized());
     assertEquals(10, (int) memoizedSupplier.get());
 
     // it still should only have executed once due to memoization
@@ -102,7 +103,7 @@ public void testMemoize() {
   }
 
   private void memoizeTest(CountingSupplier countingSupplier) {
-    Supplier<Integer> memoizedSupplier = Suppliers.memoize(countingSupplier);
+    Suppliers.MemoizingSupplier<Integer> memoizedSupplier = Suppliers.memoize(countingSupplier);
     checkMemoize(countingSupplier, memoizedSupplier);
   }
 
@@ -139,7 +140,7 @@ private void memoizeExceptionThrownTest(ThrowingSupplier throwingSupplier) {
   @GwtIncompatible // SerializableTester
   public void testMemoizeNonSerializable() throws Exception {
     CountingSupplier countingSupplier = new CountingSupplier();
-    Supplier<Integer> memoizedSupplier = Suppliers.memoize(countingSupplier);
+    Suppliers.MemoizingSupplier<Integer> memoizedSupplier = Suppliers.memoize(countingSupplier);
     assertThat(memoizedSupplier.toString()).isEqualTo("Suppliers.memoize(CountingSupplier)");
     checkMemoize(countingSupplier, memoizedSupplier);
     // Calls to the original memoized supplier shouldn't affect its copy.
@@ -156,19 +157,19 @@ public void testMemoizeNonSerializable() throws Exception {
   @GwtIncompatible // SerializableTester
   public void testMemoizeSerializable() throws Exception {
     SerializableCountingSupplier countingSupplier = new SerializableCountingSupplier();
-    Supplier<Integer> memoizedSupplier = Suppliers.memoize(countingSupplier);
+    Suppliers.MemoizingSupplier<Integer> memoizedSupplier = Suppliers.memoize(countingSupplier);
     assertThat(memoizedSupplier.toString()).isEqualTo("Suppliers.memoize(CountingSupplier)");
     checkMemoize(countingSupplier, memoizedSupplier);
     // Calls to the original memoized supplier shouldn't affect its copy.
     Object unused = memoizedSupplier.get();
     assertThat(memoizedSupplier.toString())
         .isEqualTo("Suppliers.memoize(<supplier that returned 10>)");
 
-    Supplier<Integer> copy = reserialize(memoizedSupplier);
+    Suppliers.MemoizingSupplier<Integer> copy = reserialize(memoizedSupplier);
     Object unused2 = memoizedSupplier.get();
 
     CountingSupplier countingCopy =
-        (CountingSupplier) ((Suppliers.MemoizingSupplier<Integer>) copy).delegate;
+        (CountingSupplier) ((Suppliers.SerializableMemoizingSupplier<Integer>) copy).delegate;
     checkMemoize(countingCopy, copy);
   }
 

diff --git a/guava/src/com/google/common/base/Suppliers.java b/guava/src/com/google/common/base/Suppliers.java
@@ -108,18 +108,34 @@ public String toString() {
    * <p>If {@code delegate} is an instance created by an earlier call to {@code memoize}, it is
    * returned directly.
    */
-  public static <T extends @Nullable Object> Supplier<T> memoize(Supplier<T> delegate) {
+  public static <T extends @Nullable Object> MemoizingSupplier<T> memoize(Supplier<T> delegate) {
     if (delegate instanceof NonSerializableMemoizingSupplier
-        || delegate instanceof MemoizingSupplier) {
-      return delegate;
+        || delegate instanceof SerializableMemoizingSupplier) {
+      return (MemoizingSupplier<T>) delegate;
     }
     return delegate instanceof Serializable
-        ? new MemoizingSupplier<T>(delegate)
+        ? new SerializableMemoizingSupplier<T>(delegate)
         : new NonSerializableMemoizingSupplier<T>(delegate);
   }
 
+  /**
+   * A supplier that memoizes the result of the first call to {@link #get()} and returns the same
+   * result on subsequent calls to {@link #get()}.
+   *
+   * @author Alexey Pelykh
+   */
+  @ElementTypesAreNonnullByDefault
+  public interface MemoizingSupplier<T extends @Nullable Object> extends Supplier<T> {
+    /**
+     * Returns {@code true} if the supplier has been initialized, i.e. if the first call to
+     * {@link #get()} has been made or if the supplier has been explicitly initialized.
+     */
+    boolean isMemoized();
+  }
+
   @VisibleForTesting
-  static class MemoizingSupplier<T extends @Nullable Object> implements Supplier<T>, Serializable {
+  static class SerializableMemoizingSupplier<T extends @Nullable Object>
+      implements MemoizingSupplier<T>, Serializable {
     private transient Object lock = new Object();
 
     final Supplier<T> delegate;
@@ -128,7 +144,7 @@ static class MemoizingSupplier<T extends @Nullable Object> implements Supplier<T
     // on volatile read of "initialized".
     transient @Nullable T value;
 
-    MemoizingSupplier(Supplier<T> delegate) {
+    SerializableMemoizingSupplier(Supplier<T> delegate) {
       this.delegate = checkNotNull(delegate);
     }
 
@@ -152,6 +168,11 @@ public T get() {
       return uncheckedCastNullableTToT(value);
     }
 
+    @Override
+    public boolean isMemoized() {
+      return initialized;
+    }
+
     @Override
     public String toString() {
       return "Suppliers.memoize("
@@ -170,7 +191,8 @@ private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundE
   }
 
   @VisibleForTesting
-  static class NonSerializableMemoizingSupplier<T extends @Nullable Object> implements Supplier<T> {
+  static class NonSerializableMemoizingSupplier<T extends @Nullable Object>
+      implements MemoizingSupplier<T> {
     private final Object lock = new Object();
 
     @SuppressWarnings("UnnecessaryLambda") // Must be a fixed singleton object
@@ -206,6 +228,11 @@ public T get() {
       return uncheckedCastNullableTToT(value);
     }
 
+    @Override
+    public boolean isMemoized() {
+      return delegate == SUCCESSFULLY_COMPUTED;
+    }
+
     @Override
     public String toString() {
       Supplier<T> delegate = this.delegate;