Merge pull request #931 from soot-oss/simplify/LRUCache

simplify LRUCache implementation - make use of LinkedHashmap+3rd ctor

sootup.core/src/main/java/sootup/core/cache/LRUCache.java

@@ -32,23 +32,21 @@
  * specified amount, the lest recently used class will be overwritten.
  */
 public class LRUCache implements ClassCache {
-  private final int cacheSize;
-  private final Map<ClassType, SootClass> cache = new HashMap<>();
-  private final LinkedList<ClassType> accessOrder = new LinkedList<>();
+  private final LinkedHashMap<ClassType, SootClass> cache;
 
   public LRUCache(int cacheSize) {
-    this.cacheSize = cacheSize;
+    cache =
+        new LinkedHashMap<ClassType, SootClass>(cacheSize, 1, true) {
+          @Override
+          protected boolean removeEldestEntry(Map.Entry<ClassType, SootClass> eldest) {
+            return size() > cacheSize;
+          };
+        };
   }
 
   @Override
   public synchronized SootClass getClass(ClassType classType) {
-    SootClass sootClass = cache.get(classType);
-    if (sootClass != null) {
-      accessOrder.remove(classType);
-      accessOrder.addFirst(classType);
-    }
-
-    return sootClass;
+    return cache.get(classType);
   }
 
   @Nonnull
@@ -59,12 +57,6 @@ public synchronized Collection<SootClass> getClasses() {
 
   @Override
   public void putClass(ClassType classType, SootClass sootClass) {
-    if (accessOrder.size() >= cacheSize) {
-      ClassType leastAccessed = accessOrder.removeLast();
-      cache.remove(leastAccessed);
-    }
-
-    accessOrder.addFirst(classType);
     cache.putIfAbsent(classType, sootClass);
   }