Summary

The implementation requirement of Map::compute does not match its default implementation. Besides, it has some other minor issues. We should fix it.

Problem

The documentation of the implementation requirements for Map::compute has the following problems:

1. It doesn't match its default implementation.
2. It lacks of the return statements for most of the if-else cases.
3. The indents are 3 spaces, while the convention is 4 spaces.
4. The if-else is overly complicated and can be simplified.
5. The surrounding prose contains incorrect statements.

Solution

Rewrite the documentation of Map::compute to match its default implementation and solve the above mentioned problems.

Specification

diff --git a/src/java.base/share/classes/java/util/Map.java b/src/java.base/share/classes/java/util/Map.java
index b1de34b42a5..b30e3979259 100644
--- a/src/java.base/share/classes/java/util/Map.java
+++ b/src/java.base/share/classes/java/util/Map.java
@@ -1107,23 +1107,17 @@ public interface Map<K, V> {
      *
      * @implSpec
      * The default implementation is equivalent to performing the following
-     * steps for this {@code map}, then returning the current value or
-     * {@code null} if absent:
+     * steps for this {@code map}:
      *
      * <pre> {@code
      * V oldValue = map.get(key);
      * V newValue = remappingFunction.apply(key, oldValue);
-     * if (oldValue != null) {
-     *    if (newValue != null)
-     *       map.put(key, newValue);
-     *    else
-     *       map.remove(key);
-     * } else {
-     *    if (newValue != null)
-     *       map.put(key, newValue);
-     *    else
-     *       return null;
+     * if (newValue != null) {
+     *     map.put(key, newValue);
+     * } else if (oldValue != null || map.containsKey(key)) {
+     *     map.remove(key);
      * }
+     * return newValue;
      * }</pre>
      *
      * <p>The default implementation makes no guarantees about detecting if the