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:

java.util.Map<K,V>

public class StackedHashMap<K,V>
extends java.util.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

Author:

Marcel Overdijk

See Also:

HashMap

Nested Class Summary

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

java.util.AbstractMap.SimpleEntry<K,V>, java.util.AbstractMap.SimpleImmutableEntry<K,V>

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

java.util.Map.Entry<K,V>

Field Summary

Fields

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

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and Description
void	clearStack() Clears the stack.
java.util.Set<java.util.Map.Entry<K,V>>	entrySet()
java.util.HashMap<K,V>	peek() Retrieves, but does not remove, the top element (HashMap) from the stack.
java.util.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 Detail

stack

protected java.util.Deque<java.util.HashMap<K,V>> stack

Constructor Detail

StackedHashMap

public StackedHashMap()

Constructs a new StackedHashMap.

StackedHashMap

public StackedHashMap(java.util.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 Detail

push

public void push()

Pushes a new element (HashMap) onto the stack.

pop

public java.util.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:

java.lang.IllegalStateException - if there is only 1 element on the stack

peek

public java.util.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 java.util.Map<K,V>

Overrides:

put in class java.util.AbstractMap<K,V>

entrySet

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

Specified by:

entrySet in interface java.util.Map<K,V>

Specified by:

entrySet in class java.util.AbstractMap<K,V>