Added ObjectCache class and fixed som hashmap iterator issues

src/zutil/Timer.java

@@ -44,9 +44,12 @@ public class Timer {
 
     /**
      * Will start or restart the timer if it is already running
+     *
+     * @return a reference of itself
      */
-    public void start(){
+    public Timer start(){
         timestamp = System.currentTimeMillis();
+        return this;
     }
 
     /**

src/zutil/db/bean/DBBeanSQLResultHandler.java

@@ -156,18 +156,17 @@ public class DBBeanSQLResultHandler<T> implements SQLResultHandler<T>{
 			}
 			
 			int removed = 0;
-			long time = System.currentTimeMillis();
 			for(Object classKey : cache.keySet()){
 				if( classKey == null ) continue;
 					
 				Map<Long,DBBeanCache> class_cache = cache.get(classKey);
-				for(Object objKey : class_cache.keySet()){
-					if( objKey == null ) continue;
+				for(Iterator<Map.Entry<Long, DBBeanCache>> it = class_cache.entrySet().iterator(); it.hasNext(); ) {
+					Map.Entry<Long, DBBeanCache> entry = it.next();
+					if( entry.getKey() == null ) continue;
 
-					DBBeanCache beanCache = class_cache.get(objKey);
 					// Check if session is still valid
-					if( beanCache.bean.get() == null ){
-						class_cache.remove(objKey);
+					if( entry.getValue().bean.get() == null ){
+						it.remove();
 						removed++;
 					}
 				}

src/zutil/struct/ObjectCache.java

@@ -0,0 +1,91 @@
+package zutil.struct;
+
+import zutil.Timer;
+
+import java.lang.ref.WeakReference;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map;
+
+/**
+ * This is a Object cache where objects can be stored with {@link java.lang.ref.WeakReference} and a time limit.
+ * 
+ * Created by Ziver on 2016-07-29.
+ */
+public class ObjectCache<K, V> {
+
+    private static class CacheEntry<V>{
+        public Timer timer;
+        public WeakReference<V> value;
+    }
+
+    private HashMap<K, CacheEntry<V>> cache = new HashMap<>();
+    private long ttl;
+
+
+    public ObjectCache(long ttl){
+        this.ttl = ttl;
+    }
+
+
+    /**
+     * Stores a key and value pair in the cache.
+     */
+    public void put(K key, V value){
+        CacheEntry<V> entry = new CacheEntry<>();
+        entry.timer = new Timer(ttl).start();
+        entry.value = new WeakReference<>(value);
+        cache.put(key, entry);
+    }
+
+
+    /**
+     * Checks if the specific key is available in
+     * the cache and that it is valid.
+     */
+    public boolean containsKey(Object key){
+        if(cache.containsKey(key)){
+            CacheEntry<V> entry = cache.get(key);
+            if (entry.timer.hasTimedOut() || entry.value.get() == null) // entry to old or not valid
+                cache.remove(key);
+            else
+                return true;
+        }
+        return false;
+    }
+
+
+    public V get(Object key){
+        if (containsKey(key))
+            return cache.get(key).value.get();
+        return null;
+    }
+
+
+
+    /**
+     * This method will return the number of stored entries(valid and timed out entries) in the cache.
+     */
+    public int size() {
+        return cache.size();
+    }
+
+
+
+    /**
+     * Iterates through the Set and removes all entries that has passed its TTL.
+     *
+     * @return the number of objects removed from the Set
+     */
+    public int garbageCollect(){
+        int count = 0;
+        for(Iterator<Map.Entry<K, CacheEntry<V>>> it = cache.entrySet().iterator(); it.hasNext(); ) {
+            Map.Entry<K, CacheEntry<V>> mapEntry = it.next();
+            if (mapEntry.getValue().timer.hasTimedOut() || mapEntry.getValue().value.get() == null) { // entry to old or not valid
+                it.remove();
+                ++count;
+            }
+        }
+        return count;
+    }
+}

src/zutil/struct/TimedHashSet.java

@@ -24,14 +24,18 @@
 
 package zutil.struct;
 
+import zutil.Timer;
+
 import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map;
 
 /**
  * This is a timed HashSet. Each entry has a limited time to live.
  */
 public class TimedHashSet<T> {
 
-    private HashMap<T, Long> map;
+    private HashMap<T, Timer> map;
     private long ttl;
 
     /**
@@ -47,12 +51,12 @@ public class TimedHashSet<T> {
      * @return true if the object already existed in the set which will reset the TTL.
      */
     public boolean add(T o){
-        return map.put(o, System.currentTimeMillis()) != null;
+        return map.put(o, new Timer(ttl).start()) != null;
     }
 
     public boolean contains(Object o){
         if(map.containsKey(o)){
-            if(map.get(o) + ttl < System.currentTimeMillis()) // entry to old
+            if(map.get(o).hasTimedOut()) // entry to old
                 map.remove(o);
             else
                 return true;
@@ -62,12 +66,28 @@ public class TimedHashSet<T> {
 
 
     /**
-     * Iterates through the Set and removes all entries that has passed the TTL
+     * This method will return the number of stored entries(valid and timed out entries) in the Set.
      */
-    public void garbageCollect(){
-        for(T o : map.keySet()){
-            if(map.get(o) + ttl < System.currentTimeMillis()) // entry to old
-                map.remove(o);
-        }
+    public int size() {
+        return map.size();
     }
+
+
+    /**
+     * Iterates through the Set and removes all entries that has passed its TTL.
+     *
+     * @return the number of objects removed from the Set
+     */
+    public int garbageCollect(){
+        int count = 0;
+        for(Iterator<Map.Entry<T, Timer>> it = map.entrySet().iterator(); it.hasNext(); ) {
+            Map.Entry<T, Timer> entry = it.next();
+            if (entry.getValue().hasTimedOut()) { // entry to old
+                it.remove();
+                ++count;
+            }
+        }
+        return count;
+    }
+
 }

test/zutil/struct/ObjectCacheTest.java

@@ -0,0 +1,105 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2015 Ziver Koc
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package zutil.struct;
+
+import org.junit.Test;
+
+import static junit.framework.TestCase.assertTrue;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+
+
+/**
+ * Created by Ziver on 2015-11-20.
+ */
+public class ObjectCacheTest {
+    public static final String KEY = "key";
+    public static final String OBJECT = "object";
+    public static final String KEY2 = "key2";
+    public static final String OBJECT2 = "object2";
+
+
+    @Test
+    public void emptyCache() throws InterruptedException {
+        ObjectCache cache = new ObjectCache(10);
+        assertFalse(cache.containsKey(KEY));
+        assertEquals(0, cache.size());
+    }
+
+    @Test
+    public void zeroTTL() throws InterruptedException {
+        ObjectCache cache = new ObjectCache(0);
+        cache.put(KEY, OBJECT);
+        assertEquals(1, cache.size());
+        Thread.sleep(1);
+        assertFalse(cache.containsKey(KEY));
+    }
+
+    @Test
+    public void tenMsTTL() throws InterruptedException {
+        ObjectCache cache = new ObjectCache(10);
+        cache.put(KEY, OBJECT);
+        assertEquals(OBJECT, cache.get(KEY));
+        Thread.sleep(1);
+        assertTrue(cache.containsKey(KEY));
+        Thread.sleep(10);
+        assertFalse(cache.containsKey(KEY));
+        assertEquals(0, cache.size());
+    }
+
+    @Test
+    public void oneSecTTL() throws InterruptedException {
+        ObjectCache cache = new ObjectCache(1000);
+        cache.put(KEY, OBJECT);
+        Thread.sleep(1);
+        assertTrue(cache.containsKey(KEY));
+    }
+
+    //@Test
+    // This TC does not work
+    public void javaGRC() throws InterruptedException {
+        ObjectCache cache = new ObjectCache(10000);
+        {
+            String tmp = new String("temporary obj");
+            cache.put(KEY, tmp);
+            assertEquals(1, cache.size());
+        }
+        System.gc(); // will probably not do anything
+        Thread.sleep(10);
+        assertEquals(1, cache.garbageCollect());
+    }
+
+    @Test
+    public void grc() throws InterruptedException {
+        ObjectCache cache = new ObjectCache(10);
+        cache.put(KEY, OBJECT);
+        cache.put(KEY2, OBJECT2);
+        assertEquals(2, cache.size());
+        Thread.sleep(12);
+        assertEquals(2, cache.size());
+        assertEquals(2, cache.garbageCollect());
+        assertEquals(0, cache.size());
+    }
+}

test/zutil/struct/TimedHashSetTest.java

@@ -26,6 +26,8 @@ package zutil.struct;
 
 import org.junit.Test;
 
+import static junit.framework.TestCase.assertTrue;
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 
 
@@ -34,6 +36,7 @@ import static org.junit.Assert.assertFalse;
  */
 public class TimedHashSetTest {
     public static final String ENTRY = "key";
+    public static final String ENTRY2 = "key2";
 
     @Test
     public void zeroTTL() throws InterruptedException {
@@ -48,7 +51,7 @@ public class TimedHashSetTest {
         TimedHashSet set = new TimedHashSet(10);
         set.add(ENTRY);
         Thread.sleep(1);
-        assert(set.contains(ENTRY));
+        assertTrue(set.contains(ENTRY));
         Thread.sleep(10);
         assertFalse(set.contains(ENTRY));
     }
@@ -58,6 +61,18 @@ public class TimedHashSetTest {
         TimedHashSet set = new TimedHashSet(1000);
         set.add(ENTRY);
         Thread.sleep(1);
-        assert(set.contains(ENTRY));
+        assertTrue(set.contains(ENTRY));
+    }
+
+    @Test
+    public void grc() throws InterruptedException {
+        TimedHashSet set = new TimedHashSet(10);
+        set.add(ENTRY);
+        set.add(ENTRY2);
+        assertEquals(2, set.size());
+        Thread.sleep(12);
+        assertEquals(2, set.size());
+        assertEquals(2, set.garbageCollect());
+        assertEquals(0, set.size());
     }
 }