fix code

hutool-cache/src/main/java/cn/hutool/cache/GlobalPruneTimer.java

@@ -24,7 +24,7 @@ public enum GlobalPruneTimer {
 	/**
 	 * 缓存任务计数
 	 */
-	private AtomicInteger cacheTaskNumber = new AtomicInteger(1);
+	private final AtomicInteger cacheTaskNumber = new AtomicInteger(1);
 
 	/**
 	 * 定时器

hutool-cache/src/main/java/cn/hutool/cache/impl/NoCache.java

@@ -1,10 +1,10 @@
 package cn.hutool.cache.impl;
 
-import java.util.Iterator;
-
 import cn.hutool.cache.Cache;
 import cn.hutool.core.lang.func.Func0;
 
+import java.util.Iterator;
+
 /**
  * 无缓存实现，用于快速关闭缓存
  * 
@@ -61,7 +61,17 @@ public class NoCache<K, V> implements Cache<K, V> {
 
 	@Override
 	public Iterator<V> iterator() {
-		return null;
+		return new Iterator<V>() {
+			@Override
+			public boolean hasNext() {
+				return false;
+			}
+
+			@Override
+			public V next() {
+				return null;
+			}
+		};
 	}
 	
 	@Override