Map<String, Object> mapList = new HashMap<>();用java7
时间: 2023-11-11 17:29:06 浏览: 33
您可以使用Java7的迭代器(Iterator)来遍历mapList元素,示例代码如下:
```
Iterator<Map.Entry<String, Object>> iterator = mapList.entrySet().iterator();
while (iterator.hasNext()) {
Map.Entry<String, Object> entry = iterator.next();
System.out.println("Key: " + entry.getKey() + ", Value: " + entry.getValue());
}
```
这段代码将会遍历mapList中的每一个键值对,并输出键和值。使用迭代器的好处是可以在遍历过程中删除元素,但是需要注意的是,如果在遍历过程中修改了mapList的结构(例如添加或删除元素),则会抛出ConcurrentModificationException异常。
相关问题
List<Map<String, Object>> packList = new ArrayList<Map<String,Object>>(); 遍历
可以使用 for-each 循环或者迭代器(iterator)对象来遍历 `List<Map<String, Object>>` 集合。
使用 for-each 循环遍历 `List<Map<String, Object>>` 集合:
```java
List<Map<String, Object>> packList = new ArrayList<Map<String,Object>>();
Map<String, Object> map1 = new HashMap<String, Object>();
map1.put("name", "张三");
map1.put("age", 20);
packList.add(map1);
Map<String, Object> map2 = new HashMap<String, Object>();
map2.put("name", "李四");
map2.put("age", 25);
packList.add(map2);
for (Map<String, Object> map : packList) {
System.out.println("name: " + map.get("name") + ", age: " + map.get("age"));
}
```
使用迭代器(iterator)对象遍历 `List<Map<String, Object>>` 集合:
```java
List<Map<String, Object>> packList = new ArrayList<Map<String,Object>>();
Map<String, Object> map1 = new HashMap<String, Object>();
map1.put("name", "张三");
map1.put("age", 20);
packList.add(map1);
Map<String, Object> map2 = new HashMap<String, Object>();
map2.put("name", "李四");
map2.put("age", 25);
packList.add(map2);
Iterator<Map<String, Object>> iterator = packList.iterator();
while (iterator.hasNext()) {
Map<String, Object> map = iterator.next();
System.out.println("name: " + map.get("name") + ", age: " + map.get("age"));
}
```
上述代码中,`List<Map<String, Object>>` 集合中每个元素都是一个 Map 对象,可以根据需要自行修改 Map 对象中的 key 和 value 的类型。
java 怎么解决Map<String Object>和Map<String, List<Map>>互相转换
在Java中,可以使用以下方法解决Map<String, Object>和Map<String, List<Map<String, Object>>>之间的互相转换:
1. 将Map<String, Object>转换为Map<String, List<Map<String, Object>>>:
```java
Map<String, Object> map = new HashMap<>();
// 假设map中有键值对
Map<String, List<Map<String, Object>>> convertedMap = new HashMap<>();
for (Map.Entry<String, Object> entry : map.entrySet()) {
String key = entry.getKey();
Object value = entry.getValue();
List<Map<String, Object>> list = new ArrayList<>();
Map<String, Object> innerMap = new HashMap<>();
innerMap.put(key, value);
list.add(innerMap);
convertedMap.put(key, list);
}
```
2. 将Map<String, List<Map<String, Object>>>转换为Map<String, Object>:
```java
Map<String, List<Map<String, Object>>> map = new HashMap<>();
// 假设map中有键值对
Map<String, Object> convertedMap = new HashMap<>();
for (Map.Entry<String, List<Map<String, Object>>> entry : map.entrySet()) {
String key = entry.getKey();
List<Map<String, Object>> list = entry.getValue();
if (list.size() > 0) {
Map<String, Object> innerMap = list.get(0);
Object value = innerMap.get(key);
convertedMap.put(key, value);
}
}
```