Package org.hawaiiframework.util

Class StackedHashMap<K,V>

java.lang.Object

java.util.AbstractMap<K,V>

org.hawaiiframework.util.StackedHashMap<K,V>

Type Parameters:

K - the type of keys maintained by this map

V - the type of mapped values

All Implemented Interfaces:

Map<K,V>

public class StackedHashMap<K,V>
extends AbstractMap<K,V>

A stacked HashMap implementation.

This implementation is useful if you want to add and/or remove mappings to a map, but also want to return to a previous state of the map easily.

Since:

2.0.0

See Also:

• HashMap

Nested Class Summary

Nested classes/interfaces inherited from class java.util.AbstractMap

AbstractMap.SimpleEntry<K extends Object,V extends Object>, AbstractMap.SimpleImmutableEntry<K extends Object,V extends Object>

Nested classes/interfaces inherited from interface java.util.Map

Map.Entry<K extends Object,V extends Object>

Field Summary

Fields

Modifier and Type	Field	Description
protected Deque<HashMap<K,V>>	stack

Constructor Summary

Constructors

Constructor	Description
StackedHashMap()	Constructs a new StackedHashMap.
StackedHashMap(Map<? extends K,? extends V> m)	Constructs a new StackedHashMap with the same mappings as the supplied Map.

Method Summary

Modifier and Type	Method	Description
void	clearStack()	Clears the stack.
Set<Map.Entry<K,V>>	entrySet()
HashMap<K,V>	peek()	Retrieves, but does not remove, the top element (HashMap) from the stack.
HashMap<K,V>	pop()	Pops the top element (HashMap) from the stack.
void	push()	Pushes a new element (HashMap) onto the stack.
V	put(K key, V value)
int	stackSize()	Returns the number of elements (HashMaps) on the stack.

Methods inherited from class java.util.AbstractMap

clear, clone, containsKey, containsValue, equals, get, hashCode, isEmpty, keySet, putAll, remove, size, toString, values

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map

compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, putIfAbsent, remove, replace, replace, replaceAll

Field Details

stack

protected Deque<HashMap<K,V>> stack

Constructor Details

StackedHashMap

public StackedHashMap()

Constructs a new StackedHashMap.

StackedHashMap

public StackedHashMap(Map<? extends K,? extends V> m)

Constructs a new StackedHashMap with the same mappings as the supplied Map.

Parameters:

m - the map whose mappings are to be placed in this stacked map

Method Details

push

public void push()

Pushes a new element (HashMap) onto the stack.

pop

public HashMap<K,V> pop()

Pops the top element (HashMap) from the stack. Note that the initial element cannot be popped from the stack.

Returns:

the top element of the stack

Throws:

IllegalStateException - if there is only 1 element on the stack

peek

public HashMap<K,V> peek()

Retrieves, but does not remove, the top element (HashMap) from the stack.

Returns:

the top element of the stack

stackSize

public int stackSize()

Returns the number of elements (HashMaps) on the stack. There will always be at least {code 1} element on the stack.

Returns:

the number of elements on the stack

clearStack

public void clearStack()

Clears the stack. After clearing the stack there will be 1 element (HashMap) on the stack without any mappings.

put

public V put(K key,
 V value)

Specified by:

put in interface Map<K,V>

Overrides:

put in class AbstractMap<K,V>

entrySet

public Set<Map.Entry<K,V>> entrySet()

Specified by:

entrySet in interface Map<K,V>

Specified by:

entrySet in class AbstractMap<K,V>