Styjun

Find max number you can create from an array of numbers

How to supply water to a coastal desert town with no rain and no freshwater aquifers?

Is it possible to spoof an IP address to an exact number?

Did William Shakespeare hide things in his writings?

How can a ban from entering the US be lifted?

Will electrically joined dipoles of different lengths, at right angles, behave as a multiband antenna?

How frequently do Russian people still refer to others by their patronymic (отчество)?

How to play a D major chord lower than the open E major chord on guitar?

What is the maximum amount of diamond in one Minecraft game?

Is there a standard definition of the "stall" phenomena?

Do Goblin tokens count as Goblins?

Do the 26 richest billionaires own as much wealth as the poorest 3.8 billion people?

Motorcyle Chain needs to be cleaned every time you lube it?

Isn't "Dave's protocol" good if only the database, and not the code, is leaked?

How do I check that users don't write down their passwords?

Why would "dead languages" be the only languages that spells could be written in?

Why did Super-VGA offer the 5:4 1280*1024 resolution?

Why is there paternal, for fatherly, fraternal, for brotherly, but no similar word for sons?

What is the shape of the upper boundary of water hitting a screen?

PhD: When to quit and move on?

What instances can be solved today by modern solvers (pure LP)?

Who is responsible for exterminating cockroaches in house - tenant or landlord?

LTSpice: how to setup sinusoidal or exponential voltage source?

Curve fitting when data has a sharp initial slope and then tapers off

How do I get the index of an Item in a LinkedHashMap in a List?

How do I sort a list of dictionaries by a value of the dictionary?What is the difference between Python's list methods append and extend?How do I read / convert an InputStream into a String in Java?How do I generate random integers within a specific range in Java?Difference between HashMap, LinkedHashMap and TreeMapHow to split a string in JavaHow to directly initialize a HashMap (in a literal way)?How to fix java.lang.UnsupportedClassVersionError: Unsupported major.minor versionJava 8 List<V> into Map<K, V>How to install Java 8 on Mac

.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;

-1

I have this Map

Map<String, List<OrderLine>> productsNeeded = new LinkedHashMap<>();

and I want to search in the List(s) for an Item, and then get the Key of the List where the Item was found.

java data-structures java-8 linkedhashmap

share|improve this question

edited Mar 26 at 20:22

Andronicus

7,57933 gold badges2020 silver badges3636 bronze badges

asked Mar 25 at 19:22

phil330dphil330d

1111 silver badge44 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Do you want to get the key or the index? If you want the key, this is a poor use of a map and you might be better off with a BiMap.
  
  – David Ehrmann
  Mar 25 at 19:24
  
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  You should really use a Map<OrderLine, String> instead of your map: a Map is used to find values by key, not vice versa.
  
  – JB Nizet
  Mar 25 at 19:25
  

  
  
  
  

add a comment | 

-1

I have this Map

Map<String, List<OrderLine>> productsNeeded = new LinkedHashMap<>();

and I want to search in the List(s) for an Item, and then get the Key of the List where the Item was found.

java data-structures java-8 linkedhashmap

share|improve this question

edited Mar 26 at 20:22

Andronicus

7,57933 gold badges2020 silver badges3636 bronze badges

asked Mar 25 at 19:22

phil330dphil330d

1111 silver badge44 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Do you want to get the key or the index? If you want the key, this is a poor use of a map and you might be better off with a BiMap.
  
  – David Ehrmann
  Mar 25 at 19:24
  
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  You should really use a Map<OrderLine, String> instead of your map: a Map is used to find values by key, not vice versa.
  
  – JB Nizet
  Mar 25 at 19:25
  

  
  
  
  

add a comment | 

I have this Map

Map<String, List<OrderLine>> productsNeeded = new LinkedHashMap<>();

and I want to search in the List(s) for an Item, and then get the Key of the List where the Item was found.

java data-structures java-8 linkedhashmap

share|improve this question

edited Mar 26 at 20:22

Andronicus

7,57933 gold badges2020 silver badges3636 bronze badges

asked Mar 25 at 19:22

phil330dphil330d

1111 silver badge44 bronze badges

Map<String, List<OrderLine>> productsNeeded = new LinkedHashMap<>();

share|improve this question

edited Mar 26 at 20:22

Andronicus

7,57933 gold badges2020 silver badges3636 bronze badges

asked Mar 25 at 19:22

phil330dphil330d

1111 silver badge44 bronze badges

share|improve this question

edited Mar 26 at 20:22

Andronicus

7,57933 gold badges2020 silver badges3636 bronze badges

asked Mar 25 at 19:22

phil330dphil330d

1111 silver badge44 bronze badges

edited Mar 26 at 20:22

Andronicus

7,57933 gold badges2020 silver badges3636 bronze badges

edited Mar 26 at 20:22

Andronicus

7,57933 gold badges2020 silver badges3636 bronze badges

asked Mar 25 at 19:22

phil330dphil330d

1111 silver badge44 bronze badges

asked Mar 25 at 19:22

phil330dphil330d

1111 silver badge44 bronze badges

2 Answers
2

active

oldest

votes

1

You can try this:

 productsNeeded.entrySet().stream()
 .filter(e -> e.getValue()
 .contains(matchingElement))
 .map(Map.Entry::getKey)
 .findFirst();

Provided that matchingElement is the object of type OrderLine you're looking for. Here you're getting Optional. To get value you can call get or orElse to provide a default one, for example:

 productsNeeded.entrySet().stream()
 .filter(e -> e.getValue()
 .contains(matchingElement))
 .map(Map.Entry::getKey)
 .findFirst().orElse(null);

share|improve this answer

answered Mar 25 at 19:25

AndronicusAndronicus

7,57933 gold badges2020 silver badges3636 bronze badges

add a comment | 

1

You can do this with Streams in Java 8+. I simplified this by making the inner key a List<String>:

String item = "";
Map<String, List<String>> productsNeeded = new LinkedHashMap<>();
String key = productsNeeded.entrySet().stream()
 .filter(e -> e.getValue().stream().anyMatch(item::equals))
 //Or e -> e.getValue().contains(item)
 .map(Entry::getKey)
 .findFirst()
 .orElse("");

Where you can put something else in the default value of orElse.

share|improve this answer

edited Mar 25 at 19:34

answered Mar 25 at 19:26

GBlodgettGBlodgett

11.8k44 gold badges2222 silver badges3838 bronze badges

add a comment | 

Your Answer

StackExchange.ifUsing("editor", function ()
StackExchange.using("externalEditor", function ()
StackExchange.using("snippets", function ()
StackExchange.snippets.init();
);
);
, "code-snippets");

StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "1"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);

else
createEditor();

);

function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader:
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
,
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);



);

draft saved

draft discarded

Sign up or log in

StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);

Sign up using Google

Sign up using Facebook

Sign up using Email and Password

Post as a guest

Name

Email

Required, but never shown

StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f55345045%2fhow-do-i-get-the-index-of-an-item-in-a-linkedhashmap-in-a-list%23new-answer', 'question_page');

);

Post as a guest

Name

Email

Required, but never shown

1

You can try this:

 productsNeeded.entrySet().stream()
 .filter(e -> e.getValue()
 .contains(matchingElement))
 .map(Map.Entry::getKey)
 .findFirst();

Provided that matchingElement is the object of type OrderLine you're looking for. Here you're getting Optional. To get value you can call get or orElse to provide a default one, for example:

 productsNeeded.entrySet().stream()
 .filter(e -> e.getValue()
 .contains(matchingElement))
 .map(Map.Entry::getKey)
 .findFirst().orElse(null);

share|improve this answer

answered Mar 25 at 19:25

AndronicusAndronicus

7,57933 gold badges2020 silver badges3636 bronze badges

add a comment | 

1

You can try this:

 productsNeeded.entrySet().stream()
 .filter(e -> e.getValue()
 .contains(matchingElement))
 .map(Map.Entry::getKey)
 .findFirst();

Provided that matchingElement is the object of type OrderLine you're looking for. Here you're getting Optional. To get value you can call get or orElse to provide a default one, for example:

 productsNeeded.entrySet().stream()
 .filter(e -> e.getValue()
 .contains(matchingElement))
 .map(Map.Entry::getKey)
 .findFirst().orElse(null);

share|improve this answer

answered Mar 25 at 19:25

AndronicusAndronicus

7,57933 gold badges2020 silver badges3636 bronze badges

add a comment | 

You can try this:

 productsNeeded.entrySet().stream()
 .filter(e -> e.getValue()
 .contains(matchingElement))
 .map(Map.Entry::getKey)
 .findFirst();

Provided that matchingElement is the object of type OrderLine you're looking for. Here you're getting Optional. To get value you can call get or orElse to provide a default one, for example:

 productsNeeded.entrySet().stream()
 .filter(e -> e.getValue()
 .contains(matchingElement))
 .map(Map.Entry::getKey)
 .findFirst().orElse(null);

share|improve this answer

answered Mar 25 at 19:25

AndronicusAndronicus

7,57933 gold badges2020 silver badges3636 bronze badges

 productsNeeded.entrySet().stream()
 .filter(e -> e.getValue()
 .contains(matchingElement))
 .map(Map.Entry::getKey)
 .findFirst();

 productsNeeded.entrySet().stream()
 .filter(e -> e.getValue()
 .contains(matchingElement))
 .map(Map.Entry::getKey)
 .findFirst().orElse(null);

share|improve this answer

answered Mar 25 at 19:25

AndronicusAndronicus

7,57933 gold badges2020 silver badges3636 bronze badges

answered Mar 25 at 19:25

AndronicusAndronicus

7,57933 gold badges2020 silver badges3636 bronze badges

answered Mar 25 at 19:25

AndronicusAndronicus

7,57933 gold badges2020 silver badges3636 bronze badges

1

You can do this with Streams in Java 8+. I simplified this by making the inner key a List<String>:

String item = "";
Map<String, List<String>> productsNeeded = new LinkedHashMap<>();
String key = productsNeeded.entrySet().stream()
 .filter(e -> e.getValue().stream().anyMatch(item::equals))
 //Or e -> e.getValue().contains(item)
 .map(Entry::getKey)
 .findFirst()
 .orElse("");

Where you can put something else in the default value of orElse.

share|improve this answer

edited Mar 25 at 19:34

answered Mar 25 at 19:26

GBlodgettGBlodgett

11.8k44 gold badges2222 silver badges3838 bronze badges

add a comment | 

1

You can do this with Streams in Java 8+. I simplified this by making the inner key a List<String>:

String item = "";
Map<String, List<String>> productsNeeded = new LinkedHashMap<>();
String key = productsNeeded.entrySet().stream()
 .filter(e -> e.getValue().stream().anyMatch(item::equals))
 //Or e -> e.getValue().contains(item)
 .map(Entry::getKey)
 .findFirst()
 .orElse("");

Where you can put something else in the default value of orElse.

share|improve this answer

edited Mar 25 at 19:34

answered Mar 25 at 19:26

GBlodgettGBlodgett

11.8k44 gold badges2222 silver badges3838 bronze badges

add a comment | 

You can do this with Streams in Java 8+. I simplified this by making the inner key a List<String>:

String item = "";
Map<String, List<String>> productsNeeded = new LinkedHashMap<>();
String key = productsNeeded.entrySet().stream()
 .filter(e -> e.getValue().stream().anyMatch(item::equals))
 //Or e -> e.getValue().contains(item)
 .map(Entry::getKey)
 .findFirst()
 .orElse("");

Where you can put something else in the default value of orElse.

share|improve this answer

edited Mar 25 at 19:34

answered Mar 25 at 19:26

GBlodgettGBlodgett

11.8k44 gold badges2222 silver badges3838 bronze badges

String item = "";
Map<String, List<String>> productsNeeded = new LinkedHashMap<>();
String key = productsNeeded.entrySet().stream()
 .filter(e -> e.getValue().stream().anyMatch(item::equals))
 //Or e -> e.getValue().contains(item)
 .map(Entry::getKey)
 .findFirst()
 .orElse("");

share|improve this answer

edited Mar 25 at 19:34

answered Mar 25 at 19:26

GBlodgettGBlodgett

11.8k44 gold badges2222 silver badges3838 bronze badges

answered Mar 25 at 19:26

GBlodgettGBlodgett

11.8k44 gold badges2222 silver badges3838 bronze badges

answered Mar 25 at 19:26

GBlodgettGBlodgett

11.8k44 gold badges2222 silver badges3838 bronze badges