在有些开发场景，需要对 List 对象列表进行过滤处理，并将有用的数据存放到Map中。
例如：告警对象，包含告警uuid（alarmUuid） 和 设备uuid（objUuid），需要对 objUuid = -1的告警进行过滤，并将过滤后告警数据的alarmUuid和 objUuid以键值对的形式保存到Map中。
1、告警对象定义如下：
/**
* Created by Miracle Luna on 2020/3/16
*/
public class AlarmInfoResponse {
private String alarmUuid;
private String objUuid;
public AlarmInfoResponse(String alarmUuid, String objUuid) {
this.alarmUuid = alarmUuid;
this.objUuid = objUuid;
}
public String getAlarmUuid() {
return alarmUuid;
}
public void setAlarmUuid(String alarmUuid) {
this.alarmUuid = alarmUuid;
}
public String getObjUuid() {
return objUuid;
}
public void setObjUuid(String objUuid) {
this.objUuid = objUuid;
}
@Override
public String toString() {
return "AlarmInfoResponse{" +
"alarmUuid='" + alarmUuid + '\'' +
", objUuid='" + objUuid + '\'' +
'}';
}
}
2、过滤代码如下：
/**
* Created by Miracle Luna on 2020/3/16
*/
public class LambdaFilterListToMap {
public static void main(String[] args) {
List<AlarmInfoResponse> alarmInfoResponseList = new ArrayList<>();
AlarmInfoResponse response0 = new AlarmInfoResponse("alarm0", "-1");
AlarmInfoResponse response1 = new AlarmInfoResponse("alarm1", "1");
AlarmInfoResponse response2 = new AlarmInfoResponse("alarm2", "2");
AlarmInfoResponse response3 = new AlarmInfoResponse("alarm3", "3");
alarmInfoResponseList.add(response0);
alarmInfoResponseList.add(response1);
alarmInfoResponseList.add(response2);
alarmInfoResponseList.add(response3);
// 方式1：先使用foreach遍历（遍历过程中条件判断）
Map<String, String> alarmObjUuidMap1 = new HashMap<>();
alarmInfoResponseList.forEach(alarmInfoResponse -> {
if(!"-1".equals(alarmInfoResponse.getObjUuid())) {
alarmObjUuidMap1.put(alarmInfoResponse.getAlarmUuid(), alarmInfoResponse.getObjUuid());
}
});
System.out.println("============= 方式1 ====================");
alarmObjUuidMap1.forEach((alarmUuid, objUuid) -> System.out.println(alarmUuid + " : " + objUuid));
// 方式2：使用流过滤，再使用foreach遍历
Map<String, String> alarmObjUuidMap2 = new HashMap<>();
alarmInfoResponseList.stream().
filter(alarmInfoResponse -> !"-1".equals(alarmInfoResponse.getObjUuid())).
forEach(alarmInfoResponse -> alarmObjUuidMap2.put(alarmInfoResponse.getAlarmUuid(), alarmInfoResponse.getObjUuid()));
System.out.println("\n============= 方式2 ====================");
alarmObjUuidMap2.forEach((alarmUuid, objUuid) -> System.out.println(alarmUuid + " : " + objUuid));
}
}
3、运行结果如下：
============= 方式1 ====================
alarm2 : 2
alarm1 : 1
alarm3 : 3============= 方式2 ====================
alarm2 : 2
alarm1 : 1
alarm3 : 3
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。
