Java Lambda List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：
/**
*CreatedbyMiracleLunaon2020/3/16
*/
publicclassAlarmInfoResponse{
privateStringalarmUuid;
privateStringobjUuid;
publicAlarmInfoResponse(StringalarmUuid,StringobjUuid){
this.alarmUuid=alarmUuid;
this.objUuid=objUuid;
}
publicStringgetAlarmUuid(){
returnalarmUuid;
}
publicvoidsetAlarmUuid(StringalarmUuid){
this.alarmUuid=alarmUuid;
}
publicStringgetObjUuid(){
returnobjUuid;
}
publicvoidsetObjUuid(StringobjUuid){
this.objUuid=objUuid;
}
@Override
publicStringtoString(){
return"AlarmInfoResponse{"+
"alarmUuid='"+alarmUuid+'\''+
",objUuid='"+objUuid+'\''+
'}';
}
}
2、过滤代码如下：
/**
*CreatedbyMiracleLunaon2020/3/16
*/
publicclassLambdaFilterListToMap{
publicstaticvoidmain(String[]args){
ListalarmInfoResponseList=newArrayList<>();
AlarmInfoResponseresponse0=newAlarmInfoResponse("alarm0","-1");
AlarmInfoResponseresponse1=newAlarmInfoResponse("alarm1","1");
AlarmInfoResponseresponse2=newAlarmInfoResponse("alarm2","2");
AlarmInfoResponseresponse3=newAlarmInfoResponse("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）
MapalarmObjUuidMap1=newHashMap<>();
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
MapalarmObjUuidMap2=newHashMap<>();
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毛票票。