cpsc331.collections

Interface Mapping<K,V>

All Known Subinterfaces:

Dictionary<K,V>

All Known Implementing Classes:

BSTDictionary, ChainHashMap, OpenHashMap

public interface Mapping<K,V>

Provides an interface for a mapping whose keys are of type K and whose values are of type E.

Mapping Invariant: A finite collection S of pairs (k, v) of values where k has type K and v has type V, is maintained. For each element k of K, the collection includes at most one ordered pair whose first entry is k, so that a partial function from K to V is being represented.

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Method Summary

Modifier and Type	Method and Description
default boolean	defined(K k)
V	get(K k) Returns the value associated with a given key, throwing a NoSuchElementException if no value is currently associated with the given key.
V	remove(K k) Removes the ordered pair with a given input key k, returning a NoSuchElementException and leaving the Mapping unchanged if no such ordered pair exists.
void	set(K k, V v) Sets the value associated with an input key to be an input value — replacing the value formerly associated with this key if one already exists.

Method Detail

get

V get(K k)
throws java.util.NoSuchElementException

Returns the value associated with a given key, throwing a NoSuchElementException if no value is currently associated with the given key.

Parameters:

k - the key whose value is to be returned

Returns:

the value of this key

Throws:

java.util.NoSuchElementException - if no value is defined for this key

Precondition:

1. The Mapping Invariant is satisfied.
2. A value k with type K has been provided as input.

Postcondition:

1. The Mapping Invariant is satisfied.
2. This Mapping has not been changed.
3. If this Mapping includes some ordered pair whose first entry is the input key k, then the value v that is the second entry of this ordered pair (that is, the value associated with k) is returned as output. A NoSuchElementException is thrown otherwise.

defined

default boolean defined(K k)

Parameters:

k - the key to be searched for

Returns:

true if k is found; false otherwise

Reports whether a value for an input key k is presently defined.

Precondition:

1. The Mapping Invariant is satisfied.

Postcondition:

1. The Mapping Invariant is satisfied.
2. This Mapping has not been changed.
3. If this Mapping includes some ordered pair whose first entry is the input key k, then true is returned. Otherwise, false is returned.

set

void set(K k,
         V v)

Sets the value associated with an input key to be an input value — replacing the value formerly associated with this key if one already exists.

Parameters:

k - the key for which a value is to be defined

v - the value that is to be defined to this key

Precondition:

1. The Mapping Invariant is satisfied.
2. A value k with type K and v with type V are provided as input.

Postcondition:

1. The Mapping Invariant is satisfied.
2. If this Mapping included an ordered pair whose first entry is the input value k, then this is replaced by the ordered pair (k, v). Otherwise a new ordered pair (k, v) is added. No other changes to this Mapping are made.

remove

V remove(K k)
  throws java.util.NoSuchElementException

Removes the ordered pair with a given input key k, returning a NoSuchElementException and leaving the Mapping unchanged if no such ordered pair exists.

Parameters:

k - the key for which a value is to be undefined

Returns:

the former value of this key

Throws:

java.util.NoSuchElementException - if no value was defined for this key

Precondition:

1. The Dictionary Invariant is satisfied.
2. A value k with type K is provided as input.

Postcondition:

1. The Mapping Invariant is satisfied.
2. If this Mapping includes an ordered pair (k, v) whose first entry is the input key k then this ordered pair is removed and the second entry v (that is, the value associated with this key) is returned as output; no other changes are made. Otherwise a NoSuchElementException is thrown and this Mapping is not changed at all.