[improve] [doc] Add doc for customized util class

pulsar-common/src/main/java/org/apache/pulsar/common/util/collections/ConcurrentLongHashMap.java

@@ -36,6 +36,7 @@
  * <li>Open hash map with linear probing, no node allocations to store the values
  * </ol>
  *
+ * <b>WARN: method forEach do not guarantee thread safety, nor do the keys and values method.</b>
  * @param <V>
  */
 @SuppressWarnings("unchecked")
@@ -237,6 +238,12 @@ public void clear() {
         }
     }
 
+    /**
+     * Iterate over all the entries in the map and apply the processor function to each of them.
+     * <p>
+     * <b>Warning: Do Not Guarantee Thread-Safety.</b>
+     * @param processor the processor to apply to each entry
+     */
     public void forEach(EntryProcessor<V> processor) {
         for (int i = 0; i < sections.length; i++) {
             sections[i].forEach(processor);

pulsar-common/src/main/java/org/apache/pulsar/common/util/collections/ConcurrentLongLongPairHashMap.java

@@ -36,6 +36,8 @@
  * no node allocations are required to store the keys and values, and no boxing is required.
  *
  * <p>Keys <strong>MUST</strong> be &gt;= 0.
+ * <br>
+ * <b>WARN: method forEach do not guarantee thread safety, nor do the keys and values method.</b>
  */
 public class ConcurrentLongLongPairHashMap {
 
@@ -254,6 +256,12 @@ public void clear() {
         }
     }
 
+    /**
+     * Iterate over all the entries in the map and apply the processor function to each of them.
+     * <p>
+     * <b>Warning: Do Not Guarantee Thread-Safety.</b>
+     * @param processor the processor to process the elements.
+     */
     public void forEach(BiConsumerLongPair processor) {
         for (Section s : sections) {
             s.forEach(processor);

pulsar-common/src/main/java/org/apache/pulsar/common/util/collections/ConcurrentLongPairSet.java

@@ -34,6 +34,8 @@
  * no node allocations are required to store the keys and values, and no boxing is required.
  *
  * <p>Values <b>MUST</b> be &gt;= 0.
+ * <br>
+ * <b>WARN: method forEach do not guarantee thread safety, nor does the items method.</b>
  */
 public class ConcurrentLongPairSet implements LongPairSet {
 
@@ -237,6 +239,12 @@ public void clear() {
         }
     }
 
+    /**
+     * Iterate over all the elements in the set and apply the provided function.
+     * <p>
+     * <b>Warning: Do Not Guarantee Thread-Safety.</b>
+     * @param processor the processor to process the elements
+     */
     public void forEach(LongPairConsumer processor) {
         for (int i = 0; i < sections.length; i++) {
             sections[i].forEach(processor);

pulsar-common/src/main/java/org/apache/pulsar/common/util/collections/ConcurrentOpenHashMap.java

@@ -35,6 +35,7 @@
  * <p>Provides similar methods as a {@code ConcurrentMap<K,V>} but since it's an open hash map with linear probing,
  * no node allocations are required to store the values.
  *
+ * <b>WARN: method forEach do not guarantee thread safety, nor do the keys and values method.</b>
  * @param <V>
  */
 @SuppressWarnings("unchecked")
@@ -272,6 +273,12 @@ public void clear() {
         }
     }
 
+    /**
+     * Iterate over all the entries in the map and apply the processor function to each of them.
+     * <p>
+     * <b>Warning: Do Not Guarantee Thread-Safety.</b>
+     * @param processor the function to apply to each entry
+     */
     public void forEach(BiConsumer<? super K, ? super V> processor) {
         for (int i = 0; i < sections.length; i++) {
             sections[i].forEach(processor);

pulsar-common/src/main/java/org/apache/pulsar/common/util/collections/ConcurrentOpenHashSet.java

@@ -35,6 +35,8 @@
  * <p>Provides similar methods as a {@code ConcurrentMap<K,V>} but since it's an open hash map with linear probing,
  * no node allocations are required to store the values.
  *
+ * <br>
+ * <b>WARN: method forEach do not guarantee thread safety, nor does the items method.</b>
  * @param <V>
  */
 @SuppressWarnings("unchecked")
@@ -216,6 +218,12 @@ public void clear() {
         }
     }
 
+    /**
+     * Iterate over all the elements in the set and apply the provided function.
+     * <p>
+     * <b>Warning: Do Not Guarantee Thread-Safety.</b>
+     * @param processor the function to apply to each element
+     */
     public void forEach(Consumer<? super V> processor) {
         for (int i = 0; i < sections.length; i++) {
             sections[i].forEach(processor);