Resolves mojohaus#892: Restrict the ComparableVersion cache size

pom.xml

@@ -237,6 +237,11 @@
         <artifactId>commons-lang3</artifactId>
         <version>3.12.0</version>
       </dependency>
+      <dependency>
+        <groupId>org.apache.commons</groupId>
+        <artifactId>commons-collections4</artifactId>
+        <version>4.4</version>
+      </dependency>
       <dependency>
         <groupId>org.apache.maven.plugin-testing</groupId>
         <artifactId>maven-plugin-testing-harness</artifactId>

versions-common/pom.xml

@@ -60,7 +60,10 @@
       <groupId>org.apache.commons</groupId>
       <artifactId>commons-lang3</artifactId>
     </dependency>
-
+    <dependency>
+      <groupId>org.apache.commons</groupId>
+      <artifactId>commons-collections4</artifactId>
+    </dependency>
     <dependency>
       <groupId>org.apache.maven.plugin-testing</groupId>
       <artifactId>maven-plugin-testing-harness</artifactId>

versions-common/src/main/java/org/codehaus/mojo/versions/ordering/ComparableVersion.java

@@ -29,7 +29,9 @@
 import java.util.Map;
 import java.util.Properties;
 import java.util.Stack;
-import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+
+import org.apache.commons.collections4.map.LRUMap;
 
 /**
  * Generic implementation of version comparison.
@@ -39,7 +41,9 @@
  * Note: The implementation of the maven core should be used.
  */
 public class ComparableVersion implements Comparable<ComparableVersion> {
-    private static final Map<String, ComparableVersion> CACHE = new ConcurrentHashMap<>();
+    private static final int MAX_CACHE_SIZE = 0x200;
+    private static final Map<String, ComparableVersion> CACHE = new LRUMap<>(MAX_CACHE_SIZE);
+    private static final ReentrantReadWriteLock CACHE_LOCK = new ReentrantReadWriteLock();
 
     private String value;
 
@@ -291,7 +295,21 @@ public String toString() {
      * Get a ComparableVersion representing the version in a string.
      */
     public static ComparableVersion of(String version) {
-        return CACHE.computeIfAbsent(version, ComparableVersion::new);
+        try {
+            CACHE_LOCK.readLock().lock();
+            ComparableVersion result = CACHE.get(version);
+            if (result != null) {
+                return result;
+            }
+        } finally {
+            CACHE_LOCK.readLock().unlock();
+        }
+        try {
+            CACHE_LOCK.writeLock().lock();
+            return CACHE.computeIfAbsent(version, ComparableVersion::new);
+        } finally {
+            CACHE_LOCK.writeLock().unlock();
+        }
     }
 
     /**