Update code for forthcoming nullness annotations for JDK classes.

The Guava changes include further annotations [from "On Leveraging Tests to Infer Nullable Annotations."](google/guava#6510)

PiperOrigin-RevId: 559605577

j2kt/jre/java/common/javaemul/lang/JavaMap.kt

@@ -37,13 +37,13 @@ interface JavaMap<K, V> : MutableMap<K, V> {
   // TODO(b/243046587): Rewrite to handle case in which t is not mutable
   override fun putAll(t: Map<out K, V>) = java_putAll(t as MutableMap<K, V>)
 
-  fun java_compute(key: K, remappingFunction: BiFunction<in K, in V?, out V>): V? =
+  fun java_compute(key: K, remappingFunction: BiFunction<in K, in V?, out V?>): V? =
     default_compute(key, remappingFunction)
 
   fun java_computeIfAbsent(key: K, mappingFunction: Function<in K, out V>): V =
     default_computeIfAbsent(key, mappingFunction)
 
-  fun java_computeIfPresent(key: K, remappingFunction: BiFunction<in K, in V, out V>): V? =
+  fun java_computeIfPresent(key: K, remappingFunction: BiFunction<in K, in V, out V?>): V? =
     default_computeIfPresent(key, remappingFunction)
 
   fun java_containsKey(key: Any?): Boolean
@@ -97,7 +97,7 @@ fun <K, V> MutableMap<K, V>.java_remove(key: Any?): V? = remove(key as K)
 
 fun <K, V> MutableMap<K, V>.java_compute(
   key: K,
-  mappingFunction: BiFunction<in K, in V?, out V>
+  mappingFunction: BiFunction<in K, in V?, out V?>
 ): V? =
   if (this is JavaMap) java_compute(key, mappingFunction) else default_compute(key, mappingFunction)
 
@@ -110,7 +110,7 @@ fun <K, V> MutableMap<K, V>.java_computeIfAbsent(
 
 fun <K, V> MutableMap<K, V>.java_computeIfPresent(
   key: K,
-  mappingFunction: BiFunction<in K, in V, out V>
+  mappingFunction: BiFunction<in K, in V, out V?>
 ): V? =
   if (this is JavaMap) java_computeIfPresent(key, mappingFunction)
   else default_computeIfPresent(key, mappingFunction)
@@ -150,7 +150,7 @@ private fun <K, V> MutableMap<K, V>.default_forEach(action: BiConsumer<in K, in
 
 private fun <K, V> MutableMap<K, V>.default_compute(
   key: K,
-  remappingFunction: BiFunction<in K, in V?, out V>
+  remappingFunction: BiFunction<in K, in V?, out V?>
 ): V? {
   val oldValue = this[key]
   val newValue = remappingFunction.apply(key, oldValue)
@@ -184,7 +184,7 @@ private fun <K, V> MutableMap<K, V>.default_computeIfAbsent(
 
 private fun <K, V> MutableMap<K, V>.default_computeIfPresent(
   key: K,
-  remappingFunction: BiFunction<in K, in V, out V>
+  remappingFunction: BiFunction<in K, in V, out V?>
 ): V? {
   val oldValue = this[key]
   if (oldValue != null) {

j2kt/jre/javatests/smoke/CollectionsTest.java

@@ -247,9 +247,10 @@ public boolean containsValue(@Nullable Object value) {
     // The following overrides are only there to check that the override (with the Java signatures
     // of the method) compiles.
     @Override
-    @SuppressWarnings("nullness:override.param") // Checker expects @PolyNull (missing in JSpecify)
-    public V compute(
-        K key, BiFunction<? super K, ? super @Nullable V, ? extends V> remappingFunction) {
+    @SuppressWarnings("nullness:override") // Checker expects @PolyNull (missing in JSpecify)
+    public @Nullable V compute(
+        K key,
+        BiFunction<? super K, ? super @Nullable V, ? extends @Nullable V> remappingFunction) {
       return super.compute(key, remappingFunction);
     }
 
@@ -260,9 +261,9 @@ public V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction
     }
 
     @Override
-    @SuppressWarnings("nullness:override.param") // Checker expects @PolyNull (missing in JSpecify)
-    public V computeIfPresent(
-        K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
+    @SuppressWarnings("nullness:override") // Checker expects @PolyNull (missing in JSpecify)
+    public @Nullable V computeIfPresent(
+        K key, BiFunction<? super K, ? super V, ? extends @Nullable V> remappingFunction) {
       return super.computeIfPresent(key, remappingFunction);
     }