> For the complete documentation index, see [llms.txt](https://boxlang.ortusbooks.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://boxlang.ortusbooks.com/boxlang-language/reference/built-in-functions/set/structkeyset.md).

# StructKeySet

Build a Set containing the keys of a Struct.

Key names are extracted as plain Strings via Key.getName(), so the resulting Set always holds String values. The backing variant can be configured; use "linked" to preserve the Struct's iteration order.

## Method Signature

```
StructKeySet(struct=[struct], type=[string])
```

### Arguments

| Argument | Type     | Required | Description                                                                                                                                                                              | Default   |
| -------- | -------- | -------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------- |
| `struct` | `struct` | `true`   | The struct whose keys should populate the set.                                                                                                                                           |           |
| `type`   | `string` | `false`  | <p>The backing variant: "default" / "hash" (HashSet), "linked" / "ordered" (LinkedHashSet,<br>preserves Struct iteration order), or "sorted" / "tree" (TreeSet, alphabetical order).</p> | `default` |

## Examples

### Get the keys of a struct as a Set

Returns a BoxSet containing all keys of the struct.

```java
s = { name: "Luis", age: 42, email: "x@y.z" }.keySet();
writeOutput( s.size() );

```

Result: 3

### Using the standalone function form

```java
s = structKeySet( { a: 1, b: 2, c: 3 } );
writeOutput( s.size() );

```

Result: 3

### Case sensitivity mirrors the source struct

A case-sensitive struct produces a case-sensitive key Set.

```java
cs = structNew( "casesensitive" );
cs[ "Name" ] = "Luis";
cs[ "name" ] = "Brad";
keys = cs.keySet();
writeOutput( keys.isCaseSensitive() & "," & keys.size() );

```

Result: true,2

## Related

* [BoxSetAdd](/boxlang-language/reference/built-in-functions/set/boxsetadd.md)
* [BoxSetAddAll](/boxlang-language/reference/built-in-functions/set/boxsetaddall.md)
* [BoxSetClear](/boxlang-language/reference/built-in-functions/set/boxsetclear.md)
* [BoxSetContains](/boxlang-language/reference/built-in-functions/set/boxsetcontains.md)
* [BoxSetContainsAll](/boxlang-language/reference/built-in-functions/set/boxsetcontainsall.md)
* [BoxSetDifference](/boxlang-language/reference/built-in-functions/set/boxsetdifference.md)
* [BoxSetEach](/boxlang-language/reference/built-in-functions/set/boxseteach.md)
* [BoxSetEquals](/boxlang-language/reference/built-in-functions/set/boxsetequals.md)
* [BoxSetEvery](/boxlang-language/reference/built-in-functions/set/boxsetevery.md)
* [BoxSetFilter](/boxlang-language/reference/built-in-functions/set/boxsetfilter.md)
* [BoxSetFind](/boxlang-language/reference/built-in-functions/set/boxsetfind.md)
* [BoxSetIntersection](/boxlang-language/reference/built-in-functions/set/boxsetintersection.md)
* [BoxSetIsDisjointFrom](/boxlang-language/reference/built-in-functions/set/boxsetisdisjointfrom.md)
* [BoxSetIsEmpty](/boxlang-language/reference/built-in-functions/set/boxsetisempty.md)
* [BoxSetIsSubsetOf](/boxlang-language/reference/built-in-functions/set/boxsetissubsetof.md)
* [BoxSetIsSupersetOf](/boxlang-language/reference/built-in-functions/set/boxsetissupersetof.md)
* [BoxSetMap](/boxlang-language/reference/built-in-functions/set/boxsetmap.md)
* [BoxSetNone](/boxlang-language/reference/built-in-functions/set/boxsetnone.md)
* [BoxSetReduce](/boxlang-language/reference/built-in-functions/set/boxsetreduce.md)
* [BoxSetReject](/boxlang-language/reference/built-in-functions/set/boxsetreject.md)
* [BoxSetRemove](/boxlang-language/reference/built-in-functions/set/boxsetremove.md)
* [BoxSetRemoveAll](/boxlang-language/reference/built-in-functions/set/boxsetremoveall.md)
* [BoxSetRetainAll](/boxlang-language/reference/built-in-functions/set/boxsetretainall.md)
* [BoxSetSome](/boxlang-language/reference/built-in-functions/set/boxsetsome.md)
* [BoxSetSymmetricDifference](/boxlang-language/reference/built-in-functions/set/boxsetsymmetricdifference.md)
* [BoxSetToArray](/boxlang-language/reference/built-in-functions/set/boxsettoarray.md)
* [BoxSetToList](/boxlang-language/reference/built-in-functions/set/boxsettolist.md)
* [BoxSetUnion](/boxlang-language/reference/built-in-functions/set/boxsetunion.md)
* [ObjectToSet](/boxlang-language/reference/built-in-functions/set/objecttoset.md)
* [SetNew](/boxlang-language/reference/built-in-functions/set/setnew.md)
* [SetOf](/boxlang-language/reference/built-in-functions/set/setof.md)
* [StructValueSet](/boxlang-language/reference/built-in-functions/set/structvalueset.md)
* [ToSet](/boxlang-language/reference/built-in-functions/set/toset.md)


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