eu.dnetlib.miscutils.hstree

Class TreeNode<T,N,V,C extends TreeNode<N,?,V,?>>

java.lang.Object

eu.dnetlib.miscutils.hstree.TreeNode<T,N,V,C>

Type Parameters:

T - Type of the payload (or resource)

N - Type of the next level payload

C - Type of the next level node (another TreeNode)

Direct Known Subclasses:

NilTreeNode

public class TreeNode<T,N,V,C extends TreeNode<N,?,V,?>>
extends Object

This class implement statically typed complete tree of finite depth. The type signature of each tree node determines fully the depth and the types of all the children.

 class MyTree extends TreeNode<RootPayload, L1Payload, TreeNode<L1Payload, L2Payload, TreeNode<L2Payload, Void, NilTreeNode>>> {
 
 }
 

However since java doesn't have type inferencing we'll have to write often the full type of intermediate nodes, especially during tree construction. Thus it's recommended that you split the chain into a number of dummy classes, serving only to the purpuse of declaring the type chain:

 class MyTree extends TreeNode<RootPayload, L1Payload, L1Tree> {
 }
 
 class L1Tree extends TreeNode<L1Payload, L2Payload, L2Tree> {
 }
 
 class L2Tree extends TreeNode<L2Payload, Void, NilTreeNode> {
 }
 

NOTE: you could keep the whole definition inside a single file using inner classes.

Author:

marko

Field Summary

Fields

Modifier and Type	Field and Description
static String	CHILDR_UNDER_LEAF

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	TreeNode() Default constructor doesn't set the payload.
protected	TreeNode(T resource) However the constructor is protected because users should only create objects through addChild or in alternative they should provide they own constructor ovverrides.

Method Summary

Modifier and Type	Method and Description
void	accept(V dummy)
C	addChild(N resource) Call this method to add a child node.
TreeNode<T,N,V,C>	appendChild(N resource) This method is especially useful for leaf nodes when you want to append several children to the same parent node, without having to declare a temporary variable to hold the parent node (which could have long and ugly type)
protected Class<? extends C>	autoChildNodeType(Class<? extends TreeNode> clazz) For the curious, this method takes care of retrieving the runtime type information for the tree node element declared for children nodes.
void	baseDepthFirst(V visitor)
void	breadthFirst(V visitor) This method applies a visitor to all nodes in a breadth first fashon Currently null payloads are skipped
void	depthFirst(V visitor) depth first.
List<C>	getChildren()
protected <X> X	getRawType(Type type)
T	getResource()
void	setChildren(List<C> children)
void	setResource(T resource)

Methods inherited from class java.lang.Object

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

Field Detail

CHILDR_UNDER_LEAF

public static final String CHILDR_UNDER_LEAF

See Also:

Constant Field Values

Constructor Detail

TreeNode

protected TreeNode()

Default constructor doesn't set the payload. This is used internally to construct a node. We cannot use the TreeNode(T resource) constructor only because it would force any implementor of "alias" subclasses of TreeNode to provide a dummy implementation of the constructor calling super(resource) However the constructor is protected because users should only create objects through addChild or in alternative they should provide they own constructor ovverrides.

TreeNode

protected TreeNode(T resource)

However the constructor is protected because users should only create objects through addChild or in alternative they should provide they own constructor ovverrides.

Parameters:

resource - payload

Method Detail

addChild

public C addChild(N resource)

Call this method to add a child node. Only the payload is needed, the tree node will be constructed automatically and it will be returned.

 L1Child c1 = root.addChild(new L1Resource());
 c1.addChild(new L2Resource());
 c1.addChild(new L2Resource()).addChild(new L3Resource());
 

Parameters:

resource - payload

Returns:

the new node

appendChild

public TreeNode<T,N,V,C> appendChild(N resource)

This method is especially useful for leaf nodes when you want to append several children to the same parent node, without having to declare a temporary variable to hold the parent node (which could have long and ugly type)

Parameters:

resource -

Returns:

the parent node

breadthFirst

public void breadthFirst(V visitor)

This method applies a visitor to all nodes in a breadth first fashon Currently null payloads are skipped

Parameters:

visitor -

See Also:

Visitor

depthFirst

public void depthFirst(V visitor)

depth first. Currently null payloads are skipped

Parameters:

Visitor -

See Also:

Visitor

baseDepthFirst

public void baseDepthFirst(V visitor)

autoChildNodeType

protected Class<? extends C> autoChildNodeType(Class<? extends TreeNode> clazz)

For the curious, this method takes care of retrieving the runtime type information for the tree node element declared for children nodes. Because of java type erasure, this is not strictly needed for making this kind of tree work, but it's needed if we want to enable people typing ugly long signatures and use type aliases as described in the class documentation; otherwise a cast exception would occur. Aargh, any serious language which permits type polymorphysm should have a type alias feature

Parameters:

clazz - the class object of this class

Returns:

the class object of the node element describing children

getRawType

protected <X> X getRawType(Type type)

getChildren

public List<C> getChildren()

setChildren

public void setChildren(List<C> children)

getResource

public T getResource()

setResource

public void setResource(T resource)

accept

public void accept(V dummy)