IHierarchyVisitorCallback (ph-commons 9.4.1 API)

Type Parameters:

DATATYPE - The type of object to be iterated.

All Superinterfaces:

ICallback, Serializable

All Known Implementing Classes:

DefaultHierarchyVisitorCallback
```
public interface IHierarchyVisitorCallback<DATATYPE>
extends ICallback
```
Base interface with callbacks for visiting a hierarchy.

Author:

Philip Helger

Method Summary

All Methods Instance Methods Abstract Methods Default Methods
Modifier and Type	Method and Description
`default void`	`begin()` Called before the tree walking starts.
`default void`	`end()` Called after the tree walking ended.
`int`	`getLevel()`
`EHierarchyVisitorReturn`	`onItemAfterChildren(DATATYPE aItem)` Called after eventual children of the current item were visited.
`EHierarchyVisitorReturn`	`onItemBeforeChildren(DATATYPE aItem)` Called before children of the current item are visited.
`default void`	`onLevelDown()` Called before the tree walker descends into the next tree level.
`default void`	`onLevelUp()` Called after the tree walker ascends into the previous tree level.

- Method Detail
  - begin
```
default void begin()
```
    Called before the tree walking starts.
  - getLevel
```
@Nonnegative
int getLevel()
```
    Returns:
    
    The level of the current node within the hierarchy. Always ≥ 0. The root item has level 0.
  - onLevelDown
```
default void onLevelDown()
```
    Called before the tree walker descends into the next tree level. After this call getLevel() should return a value increased by 1.
  - onLevelUp
```
default void onLevelUp()
```
    Called after the tree walker ascends into the previous tree level. After this call getLevel() should return a value decreased by 1.
  - onItemBeforeChildren
```
@Nonnull
EHierarchyVisitorReturn onItemBeforeChildren(DATATYPE aItem)
```
    Called before children of the current item are visited. This method is also to be called if no children are present at all.
    
    Parameters:
    
    aItem - The current item. May be null.
    
    Returns:
    
    A non-null status code that determines how to continue iteration.
  - onItemAfterChildren
```
@Nonnull
EHierarchyVisitorReturn onItemAfterChildren(DATATYPE aItem)
```
    Called after eventual children of the current item were visited. This method is also to be called if no children are present at all. This method has always to be called if onItemBeforeChildren(Object) was called.
    
    Parameters:
    
    aItem - The current item. May be null.
    
    Returns:
    
    A non-null status code that determines how to continue iteration.
  - end
```
default void end()
```
    Called after the tree walking ended.

Interface IHierarchyVisitorCallback<DATATYPE>

Method Summary

Method Detail

begin

getLevel

onLevelDown

onLevelUp

onItemBeforeChildren

onItemAfterChildren

end