> 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/setnew.md).

# SetNew

Create a new empty Set, optionally pre-seeded from an existing collection.

The backing variant (hash, linked, or sorted) and case-sensitivity can be configured. When no seed is provided, an empty Set of the requested variant is returned.

## Method Signature

```
SetNew(type=[string], values=[any], caseSensitive=[boolean], isSynchronized=[boolean])
```

### Arguments

| Argument         | Type      | Required | Description                                                                                                                                                                               | Default   |
| ---------------- | --------- | -------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------- |
| `type`           | `string`  | `false`  | <p>The backing variant: "default" / "hash" (HashSet), "linked" / "ordered" (LinkedHashSet,<br>preserves insertion order), or "sorted" / "tree" (TreeSet, natural ordering).</p>           | `default` |
| `values`         | `any`     | `false`  | <p>An optional seed collection (Array, Set, or anything castable to a Set). Its elements are<br>deduplicated into the new set. A single non-collection value seeds a one-element set.</p> |           |
| `caseSensitive`  | `boolean` | `false`  | Whether string element comparisons are case-sensitive. Defaults to false.                                                                                                                 | `false`   |
| `isSynchronized` | `boolean` | `false`  | Whether the set should be thread-safe (synchronized). Default is true.                                                                                                                    | `true`    |

## Examples

### Create an empty default Set

Creates a new empty hash-based Set (no ordering, fastest lookup).

```java
s = setNew();
writeOutput( s.size() );

```

Result: 0

### Create a linked (insertion-ordered) Set seeded with values

Duplicate values are automatically removed.

```java
s = setNew( type="linked", values=[ "c", "a", "b", "a" ] );
writeOutput( s.toArray().toString() );

```

Result: \[c, a, b]

### Create a sorted Set

Elements are kept in natural ascending order at all times.

```java
s = setNew( type="sorted", values=[ 9, 1, 5, 3 ] );
writeOutput( s.toArray().toString() );

```

Result: \[1, 3, 5, 9]

### Create a case-sensitive Set

By default Sets are case-insensitive. Pass `caseSensitive=true` to treat different cases as distinct elements.

```java
s = setNew( values=[ "Hello", "hello", "HELLO" ], caseSensitive=true );
writeOutput( s.size() );

```

Result: 3

### Default behavior is case-insensitive

```java
s = setNew( values=[ "Hello", "hello", "HELLO" ] );
writeOutput( s.size() );

```

Result: 1

### Create an unsynchronized (non-thread-safe) Set

Pass `isSynchronized=false` for a faster single-threaded set that skips locking overhead.

```java
s = setNew( isSynchronized=false, values=[ 1, 2, 3 ] );
writeOutput( s.size() );

```

Result: 3

## 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)
* [SetOf](/boxlang-language/reference/built-in-functions/set/setof.md)
* [StructKeySet](/boxlang-language/reference/built-in-functions/set/structkeyset.md)
* [StructValueSet](/boxlang-language/reference/built-in-functions/set/structvalueset.md)


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