List＆lt; Map＆gt; Replication: light copy and deep copy

Shallow copy ：

list A Shallow copy to list B,java An array of the same contents in points to the same address , That is, after shallow copy A And B Point to the same address . The result is , change B It will change at the same time A, Because of change B Change B The content of the address pointed to , because A Also point to the same address , therefore A And B Change together .

initialization List l1

List<Map<String, Object>> l1 = new ArrayList<>();
Map<String, Object> m1 = new HashMap<>();
Map<String, Object> m2 = new HashMap<>();
Map<String, Object> m3 = new HashMap<>();
Map<String, Object> m4 = new HashMap<>();
m1.put("name", "zhangsan");
m1.put("value", 100);
m2.put("name", "lisi");
m2.put("value", 200);
m3.put("name", "xiaoming");
m3.put("value", 300);
m4.put("name", "xiaohong");
m4.put("value", 400);
l1.add(m1);
l1.add(m2);
l1.add(m3);
l1.add(m4);

1. Traversal loop replication

List<Map<String, Object>> shallowCopyList = new ArrayList<>(l1.size());
for (Map<String, Object> map : l1) {
    shallowCopyList.add(map);
}

2. Use List Implementation class construction method

List<Map<String, Object>> shallowCopyList = new ArrayList<>(l1);

3. Use list.addAll() Method

List<Map<String, Object>> shallowCopyList = new ArrayList<>();
shallowCopyList.addAll(l1);

Deep copy ：

Deep copy is to A Copy to B At the same time , to B Create a new address , Then add the address A The content of is delivered to the address B.ListA And ListB The content is consistent , However, due to the different addresses pointed to , So change is not affected by each other .

List<Map<String, Object>> deepCopyList = new ArrayList<>(l1.size());
for (Map<String, Object> map : l1) {
    deepCopyList.add((Map<String, Object>) SerializationUtils.clone((Serializable) map));
}
deepCopyList.addAll(deepCopyList);
deepCopyList.get(0).put("value", 10086);

Results output ：

 primary List ：[{"name":"zhangsan","value":100},{"name":"lisi","value":200},{"name":"xiaoming","value":300},{"name":"xiaohong","value":400}]
 new List ：[{"value":10086,"name":"zhangsan"},{"value":200,"name":"lisi"},{"value":300,"name":"xiaoming"},{"value":400,"name":"xiaohong"}]