# Class GroupLayout.ParallelGroup

java.lang.Object
javax.swing.GroupLayout.Group
javax.swing.GroupLayout.ParallelGroup

Enclosing class:
  `GroupLayout`

public sealed class GroupLayout.ParallelGroup extends GroupLayout.Group
A `Group` that aligns and sizes its children. `ParallelGroup` aligns its children in four possible ways: along the baseline, centered, anchored to the leading edge, or anchored to the trailing edge.

## Baseline

A `ParallelGroup` that aligns its children along the baseline must first decide where the baseline is anchored. The baseline can either be anchored to the top, or anchored to the bottom of the group. That is, the distance between the baseline and the beginning of the group can be a constant distance, or the distance between the end of the group and the baseline can be a constant distance. The possible choices correspond to the `BaselineResizeBehavior` constants `CONSTANT_ASCENT` and `CONSTANT_DESCENT`.

The baseline anchor may be explicitly specified by the `createBaselineGroup` method, or determined based on the elements. If not explicitly specified, the baseline will be anchored to the bottom if all the elements with a baseline, and that are aligned to the baseline, have a baseline resize behavior of `CONSTANT_DESCENT`; otherwise the baseline is anchored to the top of the group.

Elements aligned to the baseline are resizable if they have a baseline resize behavior of `CONSTANT_ASCENT` or `CONSTANT_DESCENT`. Elements with a baseline resize behavior of `OTHER` or `CENTER_OFFSET` are not resizable.

The baseline is calculated based on the preferred height of each of the elements that have a baseline. The baseline is calculated using the following algorithm: `max(maxNonBaselineHeight, maxAscent + maxDescent)`, where the `maxNonBaselineHeight` is the maximum height of all elements that do not have a baseline, or are not aligned along the baseline. `maxAscent` is the maximum ascent (baseline) of all elements that have a baseline and are aligned along the baseline. `maxDescent` is the maximum descent (preferred height - baseline) of all elements that have a baseline and are aligned along the baseline.

A `ParallelGroup` that aligns its elements along the baseline is only useful along the vertical axis. If you create a baseline group and use it along the horizontal axis an `IllegalStateException` is thrown when you ask `GroupLayout` for the minimum, preferred or maximum size or attempt to layout the components.

Elements that are not aligned to the baseline and smaller than the size of the `ParallelGroup` are positioned in one of three ways: centered, anchored to the leading edge, or anchored to the trailing edge.

## Non-baseline `ParallelGroup`

`ParallelGroup`s created with an alignment other than `BASELINE` align elements that are smaller than the size of the group in one of three ways: centered, anchored to the leading edge, or anchored to the trailing edge.

The leading edge is based on the axis and `ComponentOrientation`. For the vertical axis the top edge is always the leading edge, and the bottom edge is always the trailing edge. When the `ComponentOrientation` is `LEFT_TO_RIGHT`, the leading edge is the left edge and the trailing edge the right edge. A `ComponentOrientation` of `RIGHT_TO_LEFT` flips the left and right edges. Child elements are aligned based on the specified alignment the element was added with. If you do not specify an alignment, the alignment specified for the `ParallelGroup` is used.

To align elements along the baseline you `createBaselineGroup`, or `createParallelGroup` with an alignment of `BASELINE`. If the group was not created with a baseline alignment, and you attempt to add an element specifying a baseline alignment, an `IllegalArgumentException` is thrown.

Since:
  1.6
See Also:
  - `GroupLayout.createParallelGroup()`
  - `GroupLayout.createBaselineGroup(boolean,boolean)`

- ## Method Summary

  Modifier and Type
  Method
  Description
  `GroupLayout.ParallelGroup`
  `addComponent(Component component)`
  Adds a `Component` to this `Group`.
  `GroupLayout.ParallelGroup`
  `addComponent(Component component, int min, int pref, int max)`
  Adds a `Component` to this `Group` with the specified size.
  `GroupLayout.ParallelGroup`
  `addComponent(Component component, GroupLayout.Alignment alignment)`
  Adds a `Component` to this `ParallelGroup` with the specified alignment.
  `GroupLayout.ParallelGroup`
  `addComponent(Component component, GroupLayout.Alignment alignment, int min, int pref, int max)`
  Adds a `Component` to this `ParallelGroup` with the specified alignment and size.
  `GroupLayout.ParallelGroup`
  `addGap(int pref)`
  Adds a rigid gap to this `Group`.
  `GroupLayout.ParallelGroup`
  `addGap(int min, int pref, int max)`
  Adds a gap to this `Group` with the specified size.
  `GroupLayout.ParallelGroup`
  `addGroup(GroupLayout.Alignment alignment, GroupLayout.Group group)`
  Adds a `Group` to this `ParallelGroup` with the specified alignment.
  `GroupLayout.ParallelGroup`
  `addGroup(GroupLayout.Group group)`
  Adds a `Group` to this `Group`.

  ### Methods declared in class Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Method Details

  - ### addGroup

    public GroupLayout.ParallelGroup addGroup(GroupLayout.Group group)
    Adds a `Group` to this `Group`.
    Overrides:
      `addGroup` in class `GroupLayout.Group`
    Parameters:
      `group` - the `Group` to add
    Returns:
      this `Group`

  - ### addComponent

    public GroupLayout.ParallelGroup addComponent(Component component)
    Adds a `Component` to this `Group`.
    Overrides:
      `addComponent` in class `GroupLayout.Group`
    Parameters:
      `component` - the `Component` to add
    Returns:
      this `Group`

  - ### addComponent

    public GroupLayout.ParallelGroup addComponent(Component component, int min, int pref, int max)
    Adds a `Component` to this `Group` with the specified size.
    Overrides:
      `addComponent` in class `GroupLayout.Group`
    Parameters:
      `component` - the `Component` to add
      `min` - the minimum size or one of `DEFAULT_SIZE` or `PREFERRED_SIZE`
      `pref` - the preferred size or one of `DEFAULT_SIZE` or `PREFERRED_SIZE`
      `max` - the maximum size or one of `DEFAULT_SIZE` or `PREFERRED_SIZE`
    Returns:
      this `Group`

  - ### addGap

    public GroupLayout.ParallelGroup addGap(int pref)
    Adds a rigid gap to this `Group`.
    Overrides:
      `addGap` in class `GroupLayout.Group`
    Parameters:
      `pref` - the size of the gap
    Returns:
      this `Group`

  - ### addGap

    public GroupLayout.ParallelGroup addGap(int min, int pref, int max)
    Adds a gap to this `Group` with the specified size.
    Overrides:
      `addGap` in class `GroupLayout.Group`
    Parameters:
      `min` - the minimum size of the gap
      `pref` - the preferred size of the gap
      `max` - the maximum size of the gap
    Returns:
      this `Group`

  - ### addGroup

    public GroupLayout.ParallelGroup addGroup(GroupLayout.Alignment alignment, GroupLayout.Group group)
    Adds a `Group` to this `ParallelGroup` with the specified alignment. If the child is smaller than the `Group` it is aligned based on the specified alignment.
    Parameters:
      `alignment` - the alignment
      `group` - the `Group` to add
    Returns:
      this `ParallelGroup`
    Throws:
      `IllegalArgumentException` - if `alignment` is `null`

  - ### addComponent

    public GroupLayout.ParallelGroup addComponent(Component component, GroupLayout.Alignment alignment)
    Adds a `Component` to this `ParallelGroup` with the specified alignment.
    Parameters:
      `component` - the `Component` to add
      `alignment` - the alignment
    Returns:
      this `Group`
    Throws:
      `IllegalArgumentException` - if `alignment` is `null`

  - ### addComponent

    public GroupLayout.ParallelGroup addComponent(Component component, GroupLayout.Alignment alignment, int min, int pref, int max)
    Adds a `Component` to this `ParallelGroup` with the specified alignment and size.
    Parameters:
      `component` - the `Component` to add
      `alignment` - the alignment
      `min` - the minimum size
      `pref` - the preferred size
      `max` - the maximum size
    Returns:
      this `Group`
    Throws:
      `IllegalArgumentException` - if `alignment` is `null`