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I have an object which has Set. Each Set of object has another object where that also has Set of object.

class GroupVO 
 int id;
 Set<MasterVO> master; // This should be changed as Map<masterId, MasterVO>

 //getter, setter


class MasterVO 
 int masterId;
 Set<SlaveVO> slave; // This should be changed as Map<slaveId, SlaveVO>

 //getter, setter


class SlaveVO 
 int slaveId;
 String title;
 String description;

 //getter, setter

And I want to convert these Set to Map.

I'm able to convert it for the first map level. But, I don't know how to get the second 'Set' to Map conversion.

GroupVO groupVO = new GroupVO();
Map<Integer, MasterVO> masterMap = groupVO.getMaster().stream()
 .collect(Collectors.toMap(MasterVO::getMasterId, Function.identity()));

Instead of Function.identity(), I need to access the mastervo object and in that Object I have to convert all the Set<Slave> to SlaveMap

Please suggest.

I need it like,
Map<Integre, MasterVO>. If I get the MasterVO object like masterMap.get(101), then it should have the SlaveMap inside.

java java-8 java-stream

share|improve this question

edited Mar 26 at 7:20

Shakthi

asked Mar 26 at 6:39

ShakthiShakthi

22111 gold badge33 silver badges1818 bronze badges

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Why can't you do the same as you did for MasterVo here?
  
  – Ravindra Ranwala
  Mar 26 at 7:07
  
  

  
  
  
  

add a comment | 

-1

0

I have an object which has Set. Each Set of object has another object where that also has Set of object.

class GroupVO 
 int id;
 Set<MasterVO> master; // This should be changed as Map<masterId, MasterVO>

 //getter, setter


class MasterVO 
 int masterId;
 Set<SlaveVO> slave; // This should be changed as Map<slaveId, SlaveVO>

 //getter, setter


class SlaveVO 
 int slaveId;
 String title;
 String description;

 //getter, setter

And I want to convert these Set to Map.

I'm able to convert it for the first map level. But, I don't know how to get the second 'Set' to Map conversion.

GroupVO groupVO = new GroupVO();
Map<Integer, MasterVO> masterMap = groupVO.getMaster().stream()
 .collect(Collectors.toMap(MasterVO::getMasterId, Function.identity()));

Instead of Function.identity(), I need to access the mastervo object and in that Object I have to convert all the Set<Slave> to SlaveMap

Please suggest.

I need it like,
Map<Integre, MasterVO>. If I get the MasterVO object like masterMap.get(101), then it should have the SlaveMap inside.

java java-8 java-stream

share|improve this question

edited Mar 26 at 7:20

Shakthi

asked Mar 26 at 6:39

ShakthiShakthi

22111 gold badge33 silver badges1818 bronze badges

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Why can't you do the same as you did for MasterVo here?
  
  – Ravindra Ranwala
  Mar 26 at 7:07
  
  

  
  
  
  

add a comment | 

I have an object which has Set. Each Set of object has another object where that also has Set of object.

class GroupVO 
 int id;
 Set<MasterVO> master; // This should be changed as Map<masterId, MasterVO>

 //getter, setter


class MasterVO 
 int masterId;
 Set<SlaveVO> slave; // This should be changed as Map<slaveId, SlaveVO>

 //getter, setter


class SlaveVO 
 int slaveId;
 String title;
 String description;

 //getter, setter

And I want to convert these Set to Map.

I'm able to convert it for the first map level. But, I don't know how to get the second 'Set' to Map conversion.

GroupVO groupVO = new GroupVO();
Map<Integer, MasterVO> masterMap = groupVO.getMaster().stream()
 .collect(Collectors.toMap(MasterVO::getMasterId, Function.identity()));

Instead of Function.identity(), I need to access the mastervo object and in that Object I have to convert all the Set<Slave> to SlaveMap

Please suggest.

I need it like,
Map<Integre, MasterVO>. If I get the MasterVO object like masterMap.get(101), then it should have the SlaveMap inside.

java java-8 java-stream

share|improve this question

edited Mar 26 at 7:20

Shakthi

asked Mar 26 at 6:39

ShakthiShakthi

22111 gold badge33 silver badges1818 bronze badges

class GroupVO 
 int id;
 Set<MasterVO> master; // This should be changed as Map<masterId, MasterVO>

 //getter, setter


class MasterVO 
 int masterId;
 Set<SlaveVO> slave; // This should be changed as Map<slaveId, SlaveVO>

 //getter, setter


class SlaveVO 
 int slaveId;
 String title;
 String description;

 //getter, setter

GroupVO groupVO = new GroupVO();
Map<Integer, MasterVO> masterMap = groupVO.getMaster().stream()
 .collect(Collectors.toMap(MasterVO::getMasterId, Function.identity()));

share|improve this question

edited Mar 26 at 7:20

Shakthi

asked Mar 26 at 6:39

ShakthiShakthi

22111 gold badge33 silver badges1818 bronze badges

share|improve this question

edited Mar 26 at 7:20

Shakthi

asked Mar 26 at 6:39

ShakthiShakthi

22111 gold badge33 silver badges1818 bronze badges

asked Mar 26 at 6:39

ShakthiShakthi

22111 gold badge33 silver badges1818 bronze badges

asked Mar 26 at 6:39

ShakthiShakthi

22111 gold badge33 silver badges1818 bronze badges

1 Answer
1

active

oldest

votes

0

If I understand the question correctly, you want a Map<Integer,Map<Integer,SlaveVO>>, where the key of the outer Map is a master ID and the key of the inner Map is a slave ID.

I suggest to create that Map by using flatMap to obtain a Stream of all the MasterVO,SlaveVO pairs. Then you can group the elements of this Stream by master ID and use Collectors.toMap to create the inner Maps.

Map<Integer,Map<Integer,SlaveVO>>
 = groupVO .getMaster()
 .stream()
 .flatMap(m -> m.getSlave()
 .stream()
 .map(s -> new SimpleEntry<MasterVO,SlaveVO>(m,s)))
 .collect(Collectors.groupingBy(e -> e.getKey().getID(),
 Collectors.toMap(e -> e.getValue().getID(),
 Map.Entry::getValue)));

share|improve this answer

edited Mar 26 at 7:02

answered Mar 26 at 6:56

EranEran

303k3939 gold badges516516 silver badges590590 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Hi. I want Map<Integre, MasterVO> only. If I get the MasterVO object like masterMap.get(101), then it should have the SlaveMap inside.
  
  – Shakthi
  Mar 26 at 7:03
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Shakthi But your MasterVO class has no Map<Integer,SlaveVO> property. Do you intend to change that class?
  
  – Eran
  Mar 26 at 7:05
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Can't we create dynamically in the new Map object which I create is? I don't have Map in the MasterVO also. But, still we are converting Set as Map. Similarly, why can't we create a Map object in the child and can assign it to the Master?
  
  – Shakthi
  Mar 26 at 7:10
  

  
  
  
  

add a comment | 

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0

If I understand the question correctly, you want a Map<Integer,Map<Integer,SlaveVO>>, where the key of the outer Map is a master ID and the key of the inner Map is a slave ID.

I suggest to create that Map by using flatMap to obtain a Stream of all the MasterVO,SlaveVO pairs. Then you can group the elements of this Stream by master ID and use Collectors.toMap to create the inner Maps.

Map<Integer,Map<Integer,SlaveVO>>
 = groupVO .getMaster()
 .stream()
 .flatMap(m -> m.getSlave()
 .stream()
 .map(s -> new SimpleEntry<MasterVO,SlaveVO>(m,s)))
 .collect(Collectors.groupingBy(e -> e.getKey().getID(),
 Collectors.toMap(e -> e.getValue().getID(),
 Map.Entry::getValue)));

share|improve this answer

edited Mar 26 at 7:02

answered Mar 26 at 6:56

EranEran

303k3939 gold badges516516 silver badges590590 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Hi. I want Map<Integre, MasterVO> only. If I get the MasterVO object like masterMap.get(101), then it should have the SlaveMap inside.
  
  – Shakthi
  Mar 26 at 7:03
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Shakthi But your MasterVO class has no Map<Integer,SlaveVO> property. Do you intend to change that class?
  
  – Eran
  Mar 26 at 7:05
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Can't we create dynamically in the new Map object which I create is? I don't have Map in the MasterVO also. But, still we are converting Set as Map. Similarly, why can't we create a Map object in the child and can assign it to the Master?
  
  – Shakthi
  Mar 26 at 7:10
  

  
  
  
  

add a comment | 

0

If I understand the question correctly, you want a Map<Integer,Map<Integer,SlaveVO>>, where the key of the outer Map is a master ID and the key of the inner Map is a slave ID.

I suggest to create that Map by using flatMap to obtain a Stream of all the MasterVO,SlaveVO pairs. Then you can group the elements of this Stream by master ID and use Collectors.toMap to create the inner Maps.

Map<Integer,Map<Integer,SlaveVO>>
 = groupVO .getMaster()
 .stream()
 .flatMap(m -> m.getSlave()
 .stream()
 .map(s -> new SimpleEntry<MasterVO,SlaveVO>(m,s)))
 .collect(Collectors.groupingBy(e -> e.getKey().getID(),
 Collectors.toMap(e -> e.getValue().getID(),
 Map.Entry::getValue)));

share|improve this answer

edited Mar 26 at 7:02

answered Mar 26 at 6:56

EranEran

303k3939 gold badges516516 silver badges590590 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Hi. I want Map<Integre, MasterVO> only. If I get the MasterVO object like masterMap.get(101), then it should have the SlaveMap inside.
  
  – Shakthi
  Mar 26 at 7:03
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Shakthi But your MasterVO class has no Map<Integer,SlaveVO> property. Do you intend to change that class?
  
  – Eran
  Mar 26 at 7:05
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Can't we create dynamically in the new Map object which I create is? I don't have Map in the MasterVO also. But, still we are converting Set as Map. Similarly, why can't we create a Map object in the child and can assign it to the Master?
  
  – Shakthi
  Mar 26 at 7:10
  

  
  
  
  

add a comment | 

If I understand the question correctly, you want a Map<Integer,Map<Integer,SlaveVO>>, where the key of the outer Map is a master ID and the key of the inner Map is a slave ID.

I suggest to create that Map by using flatMap to obtain a Stream of all the MasterVO,SlaveVO pairs. Then you can group the elements of this Stream by master ID and use Collectors.toMap to create the inner Maps.

Map<Integer,Map<Integer,SlaveVO>>
 = groupVO .getMaster()
 .stream()
 .flatMap(m -> m.getSlave()
 .stream()
 .map(s -> new SimpleEntry<MasterVO,SlaveVO>(m,s)))
 .collect(Collectors.groupingBy(e -> e.getKey().getID(),
 Collectors.toMap(e -> e.getValue().getID(),
 Map.Entry::getValue)));

share|improve this answer

edited Mar 26 at 7:02

answered Mar 26 at 6:56

EranEran

303k3939 gold badges516516 silver badges590590 bronze badges

Map<Integer,Map<Integer,SlaveVO>>
 = groupVO .getMaster()
 .stream()
 .flatMap(m -> m.getSlave()
 .stream()
 .map(s -> new SimpleEntry<MasterVO,SlaveVO>(m,s)))
 .collect(Collectors.groupingBy(e -> e.getKey().getID(),
 Collectors.toMap(e -> e.getValue().getID(),
 Map.Entry::getValue)));

share|improve this answer

edited Mar 26 at 7:02

answered Mar 26 at 6:56

EranEran

303k3939 gold badges516516 silver badges590590 bronze badges

answered Mar 26 at 6:56

EranEran

303k3939 gold badges516516 silver badges590590 bronze badges

answered Mar 26 at 6:56

EranEran

303k3939 gold badges516516 silver badges590590 bronze badges