JavaLambdaList转Map代码实例

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 + '\\'' + \ '}'; }}

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 alarmInfoResponseList = new ArrayList<>(); AlarmInfoResponse response0 = new AlarmInfoResponse(\"alarm0\ AlarmInfoResponse response1 = new AlarmInfoResponse(\"alarm1\ AlarmInfoResponse response2 = new AlarmInfoResponse(\"alarm2\ AlarmInfoResponse response3 = new AlarmInfoResponse(\"alarm3\ 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 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 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 : 2alarm1 : 1alarm3 : 3

============= ⽅式2 ====================alarm2 : 2alarm1 : 1alarm3 : 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。