GroupLayout (Java SE 23 & JDK 23)
Description: declaration: module: java.base, package: java.lang.foreign, interface: GroupLayout
Keywords: java.lang.foreign.GroupLayout interface

# Interface GroupLayout

All Superinterfaces:
  `MemoryLayout`

All Known Subinterfaces:
  `StructLayout`, `UnionLayout`

public sealed interface GroupLayout extends MemoryLayout permits StructLayout, UnionLayout
A compound layout that is an aggregation of multiple, heterogeneous member layouts. There are two ways in which member layouts can be combined: if member layouts are laid out one after the other, the resulting group layout is a struct layout; conversely, if all member layouts are laid out at the same starting offset, the resulting group layout is a union layout.

Implementation Requirements:
  This class is immutable, thread-safe and value-based.
Sealed Class Hierarchy Graph:
Since:
  22

- ## Nested Class Summary

  ### Nested classes/interfaces declared in interface java.lang.foreign.MemoryLayout

  `MemoryLayout.PathElement`

- ## Method Summary

  Modifier and Type
  Method
  Description
  `List<MemoryLayout>`
  `memberLayouts()`
  Returns the member layouts of this group layout.
  `GroupLayout`
  `withByteAlignment(long byteAlignment)`
  Returns a memory layout with the same characteristics as this layout, but with the given alignment constraint (in bytes).
  `GroupLayout`
  `withName(String name)`
  Returns a memory layout with the same characteristics as this layout, but with the given name.
  `GroupLayout`
  `withoutName()`
  Returns a memory layout with the same characteristics as this layout, but with no name.

  ### Methods declared in interface java.lang.foreign.MemoryLayout

  `arrayElementVarHandle, byteAlignment, byteOffset, byteOffsetHandle, byteSize, equals, hashCode, name, scale, scaleHandle, select, sliceHandle, toString, varHandle`

- ## Method Details

  - ### memberLayouts

    List<MemoryLayout> memberLayouts()
    Returns the member layouts of this group layout.
    API Note:
      the order in which member layouts are returned is the same order in which member layouts have been passed to one of the group layout factory methods (see `MemoryLayout.structLayout(MemoryLayout...)` and `MemoryLayout.unionLayout(MemoryLayout...)`).
    Returns:
      the member layouts of this group layout

  - ### withName

    GroupLayout withName(String name)
    Returns a memory layout with the same characteristics as this layout, but with the given name.
    Specified by:
      `withName` in interface `MemoryLayout`
    Parameters:
      `name` - the layout name
    Returns:
      a memory layout with the same characteristics as this layout, but with the given name
    See Also:
      - `MemoryLayout.name()`

  - ### withoutName

    GroupLayout withoutName()
    Returns a memory layout with the same characteristics as this layout, but with no name.
    Specified by:
      `withoutName` in interface `MemoryLayout`
    Returns:
      a memory layout with the same characteristics as this layout, but with no name
    See Also:
      - `MemoryLayout.name()`

  - ### withByteAlignment

    GroupLayout withByteAlignment(long byteAlignment)
    Returns a memory layout with the same characteristics as this layout, but with the given alignment constraint (in bytes).
    Specified by:
      `withByteAlignment` in interface `MemoryLayout`
    Parameters:
      `byteAlignment` - the layout alignment constraint, expressed in bytes
    Returns:
      a memory layout with the same characteristics as this layout, but with the given alignment constraint (in bytes)
    Throws:
      `IllegalArgumentException` - if `byteAlignment` is not a power of two
      `IllegalArgumentException` - if `byteAlignment` is less than `M`, where `M` is the maximum alignment constraint in any of the member layouts associated with this group layout