CODEWITHSUNDEEP
javajava-stream
Ojasv singh
Ojasv singh

Reputation: 544

Merge two streams to get result

I have a list of model Config which looks like

class Config extends Model{
String name;
String type;
JsonNode config;
}

On querying the db, I get config for name 'abc' (which is passed by user) and id 'default'. There can be 3 config types (type1, type2, type3)

Requirement: If any config type is missing for the user input, config from 'default' is returned. For example: On querying for only name 'abc', I get

[
  {
    "name": "abc",
    "type": "type1",
    "config": []
  },
  {
    "name": "abc",
    "type": "type2",
    "config": []
  }
]

[
  {
    "name": "default",
    "type": "type1",
    "config": []
  },
  {
    "name": "default",
    "type": "type2",
    "config": []
  }
  {
    "name": "default",
    "type": "type3",
    "config": []
  }
]

As config of type3 is missing response should be

[
  {
    "name": "abc",
    "type": "type1",
    "config": []
  },
  {
    "name": "abc",
    "type": "type2",
    "config": []
  },
  {
    "name": "default",
    "type": "type3",
    "config": []
  }
]

What I have done:

I have a map <id, Config>. In a db query, I fetch Config for both id 1 and 0 in a list.

Map<String, JsonNode> customConfig = configList.stream()
            .filter(o -> o.getOrgId().equals(1))
            .collect(Collectors.toMap(Config::getKey, Config::getValue));
Map<String, JsonNode> defaultConfig = configList.stream()
                .filter(o -> o.getId().equals(0))
                .collect(Collectors.toMap(Config::getKey, Config::getValue));

And then I just do

configList.getOrDefault(type, defaultConfig.get(type));

What I want to do:

I want to merge the two streams into a single stream.

What I've tried: I looked into using groupingBy along with collectingAndThen in collectors but got confused on how to get the final result.

Upvotes: 1

Views: 130

Answers (1)

Arkaitz
Arkaitz

Reputation: 106

If you are on the same method you can directly filter by the two options:

Map<String, JsonNode> customConfig = configList.stream()
        .filter(o -> o.getOrgId().equals(1) || o.getOrgId().equals(0))
        .collect(Collectors.toMap(Config::getKey, Config::getValue));

Another option is to return a stream and use the concat option:

Stream<Config> stream1 = configList.stream()
        .filter(o -> o.getOrgId().equals(1));
Stream<Config> stream2 = configList.stream()
            .filter(o -> o.getId().equals(0));
Map<String, JsonNode> config = Stream.concat(stream1, stream2)
            .collect(Collectors.toMap(Config::getKey, Config::getValue));

Upvotes: 1

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