Adding and removing constraints for HL

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You can add constraints to the Hierarchical Layout in Java™ . You allocate a new constraint object and call this method on the IlvHierarchicalLayout instance:

void addConstraint(IlvHierarchicalConstraint constraint);

You can add as many constraints as you want. The constraints are respected during the subsequent layout calls until you remove them. To remove the most recent constraint, call:

void removeConstraint();

To remove a specific constraint, call:

void removeConstraint(IlvHierarchicalConstraint constraint);

To remove all existing constraints, call:

void removeAllConstraints();

You can retrieve the constraints that were added to a Hierarchical Layout with the method:

Enumeration getConstraints()

Node groups

Some constraints affect single nodes. Other constraints affect groups of nodes. The class IlvNodeGroup is a convenient way to specify a group of nodes in Java. You can create a group of nodes in the following way:

group = new IlvNodeGroup();
while (...) {
    group.add(node);
}

A node group has a similar functionality to a vector. You can ask for the size and elements of the group, remove elements from the group, or check whether a node already belongs to the group. You can also convert a vector of nodes into a group:

`group.add(node)`	Adds a node to the group.
`group.remove(node)`	Removes a node from the group.
`group.contains(node)`	Checks whether a node is in the group.
`group.size()`	Returns the number of nodes in the group.
`group.elements()`	Returns the nodes of the group as an Enumeration.
`group = new IlvNodeGroup(vector)`	Creates a group that contains the nodes stored in the input vector.

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Hierarchical Layout (HL)