!1170 MapUtil添加按固定大小划分Map的方法

Merge pull request !1170 from 晨晨/v5-dev

hutool-core/src/main/java/cn/hutool/core/map/MapUtil.java

@@ -1519,4 +1519,30 @@ public static <K, V> V computeIfAbsentForJdk8(final Map<K, V> map, final K key,
 		}
 		return value;
 	}
+
+	/**
+     * 将一个Map按照固定大小拆分成多个子Map
+     *
+     * @param map  Map
+     * @param size 子Map的大小
+     * @return 子Map列表
+     */
+	public static <K, V> List<Map<K, V>> partition(Map<K, V> map, int size) {
+        if (map == null) {
+            throw new NullPointerException("Map must not be null");
+        } else if (size <= 0) {
+            throw new IllegalArgumentException("Size must be greater than 0");
+        }
+        List<Map<K, V>> list = new ArrayList<>();
+        Iterator<Map.Entry<K, V>> iterator = map.entrySet().iterator();
+        while (iterator.hasNext()) {
+            Map<K, V> subMap = new HashMap<>(size);
+            for (int i = 0; i < size && iterator.hasNext(); i++) {
+                Map.Entry<K, V> entry = iterator.next();
+                subMap.put(entry.getKey(), entry.getValue());
+            }
+            list.add(subMap);
+        }
+        return list;
+    }
 }