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Java
The Java API wrapper is useful for Java developers who wish to seamlessly integrate the what3words API into their Java applications, without the hassle of having to manage the low level API calls themselves.
The what3words API is a fast, simple interface which allows you to convert 3 word addresses such as ///index.home.raft to latitude and longitude coordinates such as (-0.203586, 51.521251
) and vice versa. It features a powerful autosuggest function, which can validate and autocorrect user input and limit it to certain geographic areas (this powers the search box on our map site). It allows you to request a section of the what3words grid (which can be requested as GeoJSON for easy display on online maps), and to request the list of all languages supported by what3words. For advanced users, autosuggest can be used to post-process voice output. See links on the left to navigate.
All coordinates are latitude,longitude pairs in standard WGS-84 (as commonly used worldwide in GPS systems). All latitudes must be in the range of -90 to 90 (inclusive).
Installation
The library is available through Maven Central. Please add one of the following to either your pom.xml
or gradle.build
files.
Maven:
<dependency> <groupId>com.what3words</groupId> <artifactId>w3w-java-wrapper</artifactId> <version>3.1.8</version> </dependency>
Gradle:
dependencies { compile('com.what3words:w3w-java-wrapper:3.1.8') // Other dependencies your app might use }
Setup
Instantiate an instance of What3WordsV3, from which all API requests can be made
// For all requests a what3words API key is needed What3WordsV3 api = new What3WordsV3("what3words-api-key");
Usage
Convert to 3 word address
This function converts coordinates (expressed as latitude and longitude) to a 3 word address.
More information about convertTo3wa
, including returned results is available in the what3words REST API documentation.
Find the words for (51.508344,0.12549900
):
// Convert coordinates to a 3 word address ConvertTo3WA words = api.convertTo3wa(new Coordinates(51.508344, -0.12549900)) .language("en") .execute(); System.out.println("Words: " + words);
Convert to coordinates
This function converts a 3 word address to a position, expressed as coordinates of latitude and longitude.
This function takes the words parameter as a string of 3 words 'table.book.chair'
More information about convertToCoordinates
, including returned results is available in the what3words REST API documentation.
Find the words for ///filled.count.soap:
// Convert a 3 word address to coordinates ConvertToCoordinates coordinates = api.convertToCoordinates("filled.count.soap") .execute(); System.out.println("Coordinates: " + coordinates);
AutoSuggest
When presented with a 3 word address that may be incorrectly entered, AutoSuggest returns a list of potential correct 3 word addresses. It needs the first two words plus at least the first character of the third word to produce suggestions.
This method provides corrections for mis-typed words (including plural vs singular), and words being in the wrong order.
Optionally, clipping can narrow down the possibilities, and limit results to:
- One or more countries
- A geographic area (a circle, box or polygon)
This dramatically improves results, so we recommend that you use clipping if possible.
To improve results even further, set the focus
to user’s current location. This will make autosuggest
return results which are closer to the user.
More information about autosuggest
, including returned results is available in the what3words REST API documentation.
Example: Basic Autosuggest call
Autosuggest autosuggest = api.autosuggest("fun.with.code") .execute(); System.out.println("Autosuggest: " + autosuggest);
Example: AutoSuggest, clipping the results returned to France and Germany
Autosuggest autosuggest = api.autosuggest("fun.with.code") .clipToCountry("FR", "DE") .execute(); System.out.println("Autosuggest: " + autosuggest);
Example: AutoSuggest, Focus on (51.4243877,-0.34745
)
Autosuggest autosuggest = api.autosuggest("fun.with.code") .focus(new Coordinates(51.4243877,-0.34745)) .execute(); System.out.println("Autosuggest: " + autosuggest);
Example: AutoSuggest, with Generic Voice input type
Autosuggest autosuggest = api.autosuggest("fun with code") .inputType(AutosuggestInputType.GENERIC_VOICE) .language("en") .execute(); System.out.println("Autosuggest: " + autosuggest);
Grid section
Grid Section returns a section of the what3words 3m x 3m grid as a set of horizontal and vertical lines covering the requested area, which can then be drawn onto a map.
The requested box must not exceed 4km from corner to corner, or a BadBoundingBoxTooBig
error will be returned.
More information about gridSection
, including returned results is available in the what3words REST API documentation.
Get a grid for (51.527649, -0.191746
) in the south-west, and (51.515900, -0.212517
in the north-east:
// Obtain a grid section within the provided bounding box GridSection gridSection = api.gridSection( new BoundingBox( new Coordinates(51.515900, -0.212517), new Coordinates(51.527649, -0.191746) ) ).execute(); System.out.println("Grid section: " + gridSection);
Serializing To GeoJSON
If GeoJSON format is required (you are using on a map in an app for example) a function such as geoJsonSerializer
can be added. This should be registered to Gson as a TypeAdapter
and then you can then serialize the objects returned from the wrapper into GeoJSON.
JsonSerializer<GridSection> geoJsonSerializer = api.getGridSectionJsonSerializer(); GsonBuilder gsonBuilder = new GsonBuilder(); gsonBuilder.registerTypeAdapter(GridSection.class, geoJsonSerializer); Gson geoJsonGson = gsonBuilder.create(); String geoJson = geoJsonGson.toJson(gridSection);
Available languages
This function returns the currently supported languages. It will return the two letter code, and the name of the language both in that language and in English.
More information about availableLanguages
, including returned results is available in the what3words REST API documentation.
// Obtain the list of available languages AvailableLanguages languages = api.availableLanguages().execute(); System.out.println("Languages: " + languages);
Handling errors
Errors returned from the API can be caught with the wrapper through the use of a catch
function.
Within the catch
function, code
and message
values which represent the error, are accessible from the error
object parameter
Autosuggest autosuggest = api.autosuggest("freshen.overlook.clo") .clipToCountry("fr") .execute(); if (autosuggest.isSuccessful()) { ... } else { // An error occurred What3WordsError error = autosuggest.getError(); if (error == What3WordsError.BAD_CLIP_TO_COUNTRY) { // Invalid country clip is provided System.out.println("BadClipToCountry: " + error.getMessage()); } }