英文:
Java 8 iterate nested loop and fetch details
问题
public class Data {
private List<SubscriberList> subscriberCriteriaList;
}
public class SubscriberList {
private String mdn;
private List<SubscriberCriteriaList> subscriberCriteriaList;
}
public class SubscriberCriteriaList {
private String status;
private String msg;
}
{
"subscriberList": [
{
"mdn": "string",
"subscriberCriteriaList": [
{
"status": "FAIL",
"msg": "error message"
}
]
}
]
}
英文:
I have a model object which contains nested arrays and i want to retrieve some details within that model .How to collect property msg from subscriberCriteriaList into an array where subscriberCriteriaList.status is FAIL. I would expect java 8 solution for the same ? Below is the sample model objects and the corresponding json structure .
public class Data{
private List<subscriberList> subscriberCriteriaList;
}
public class subscriberList{
private String mdn;
private List<SubscriberCriteriaList> subscriberCriteriaList;
}
public class SubscriberCriteriaList{
private String status;
private String msg;
}
Sample json structure
{
"subscriberList": [
{
"mdn": "string",
"subscriberCriteriaList": [
{
"status": "FAIL",
"msg": "error message"
}
]
}
]
}
答案1
得分: 1
假设顶层对象的类型为 Data，并且所有提及的类中都有适当的获取器（getter），可以对嵌套的列表应用 flatMap，并按 status 值进行过滤：
String[] failureMessages = data.getSubscriberCriteriaList()
.stream() // Stream<subscriberList>
.flatMap(sl -> sl.getSubscriberCriteriaList().stream()) // Stream<SubscriberCriteriaList>
.filter(scl -> "FAIL".equals(scl.getStatus()))
.map(SubscriberCriteriaList::getMsg) // 映射为消息
.distinct() // （可选）如果需要，去除重复项
.toArray(String[]::new);
英文:
Assuming that the top-level object has type Data, and appropriate getters are available in all the mentioned classes, it is possible to apply flatMap to the nested lists and filter by status value:
String[] failureMessages = data.getSubscriberCriteriaList()
.stream() // Stream<subscriberList>
.flatMap(sl -> sl.getSubscriberCriteriaList().stream()) // Stream<SubscriberCriteriaList>
.filter(scl -> "FAIL".equals(scl.getStatus()))
.map(SubscriberCriteriaList::getMsg) // map to messages
.distinct() // (optionally) remove duplicates if necessary
.toArray(String[]::new);
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