Class

# OutOfBoundsException

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## Description

Occurs when code tries to access by index an item that doesn't exist. This could be an element of an array or when making a framework call that requires an index.

## Properties

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| Name                                            | Type                               | Read-Only | Shared |
|-------------------------------------------------|------------------------------------|-----------|--------|
| `ErrorNumber<outofboundsexception.errornumber>` | `Integer</api/data_types/integer>` |           |        |
| `Message<outofboundsexception.message>`         | `String</api/data_types/string>`   |           |        |

## Methods

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| Name                                             | Parameters                                                                                              | Returns                                    | Shared |
|--------------------------------------------------|---------------------------------------------------------------------------------------------------------|--------------------------------------------|--------|
| `Constructor<outofboundsexception.constructor0>` | message As `String</api/data_types/string>` = "", errorNumber As `Integer</api/data_types/integer>` = 0 |                                            |        |
| `Stack<outofboundsexception.stack>`              |                                                                                                         | `String()</api/data_types/string>`         |        |
| `StackFrames<outofboundsexception.stackframes>`  |                                                                                                         | `StackFrame()</api/exceptions/stackframe>` |        |

## Property descriptions

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OutOfBoundsException.ErrorNumber

**ErrorNumber** As `Integer</api/data_types/integer>`

> Used to contain an error number that describes the runtime error.

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OutOfBoundsException.Message

**Message** As `String</api/data_types/string>`

> Used to contain descriptive text to display when the runtime exception is encountered.

## Method descriptions

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OutOfBoundsException.Constructor

**Constructor**(message As `String</api/data_types/string>` = "", errorNumber As `Integer</api/data_types/integer>` = 0)

> <div class="note">
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> <div class="title">
>
> Note
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> `Constructors</api/language/constructor>` are special methods called when you create an object with the `New</api/language/new>` keyword and pass in the parameters above.
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> Used to raise your own `RuntimeException</api/exceptions/runtimeexception>` with a *message* and optional error number.

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OutOfBoundsException.Stack

**Stack** As `String()</api/data_types/string>`

> Returns a `String</api/data_types/string>` array that contains a list of all of the methods in the stack from the main entrypoint to the point at which the exception was invoked.
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> The stack contains all the method names up and including the current method name.
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> This feature only works if the **IncludeFunctionNames** property on the App object is selected in the Shared Build Settings.
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> In addition to your own method calls, you will also see framework method calls, but these may not always be completely accurate due to insufficient symbols for the OS to resolve.

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OutOfBoundsException.StackFrames

**StackFrames** As `StackFrame()</api/exceptions/stackframe>`

> Returns an array containing the stack when the exception was first raised.

## Notes

An <span class="title-ref">OutOfBoundsException</span> error occurs when your code uses an array index that is out of range. This occurs, for example, if you forget that arrays are zero-based and you make an error when you try to access the last element.

It can also occur when using an invalid index with a method that uses an index as a parameter. For example, if `System.FontCount<system.fontcount>` returns 100, you have 100 fonts installed. If you call `System.FontAt(150)<system.fontat>`, an <span class="title-ref">OutOfBoundsException</span> exception will be raised because there is not font at that index.

## Sample code

This example is supposed to display the fonts installed on the user's computer in a `ListBox</api/user_interface/desktop/desktoplistbox>`. It generates an <span class="title-ref">OutOfBoundsException</span> because the loop should be from 0 to nFonts-1 rather than from 1 to nFonts. When the loop gets to nFonts, the value of i is out of range and the error occurs.

``` xojo
Var nFonts As Integer
nFonts = System.FontCount
For i As Integer = 1 To nFonts
  ListBox1.Addrow(System.FontAt(i))
Next
```

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If you run this code in a built application, you will see a generic error message when i reaches the value of nFonts:

An exception of class <span class="title-ref">OutOfBoundsException</span> was not handled. The application must shut down.

You can handle the exception by adding the following code:

``` xojo
Var nFonts As Integer
nFonts = System.FontCount
For i = 1 To nFonts
  ListBox1.AddRow(System.FontAt(i))
Next

Exception err
If err IsA OutOfBoundsException Then
  MessageBox("The value: " + i.ToString + " is out of range!")
End If
```

## Compatibility

|                       |     |
|-----------------------|-----|
| **Project Types**     | All |
| **Operating Systems** | All |

<div class="seealso">

`RuntimeException</api/exceptions/runtimeexception>` parent class; `Function</api/language/function>`, `Raise</api/language/raise>`, `Sub</api/language/sub>` statements; `Nil</api/language/nil>` datatype, `Exception</api/exceptions/exception>`, `Try</api/language/try>` statements.

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