A KeyValuePair in Java [duplicate]

I'm looking for a KeyValuePair class in Java.
Since java.util heavily uses interfaces there is no concrete implementation provided, only the Map.Entry interface.

Is there some canonical implementation I can import? It is one of those "plumbers programming" classes I hate to implement 100x times.

10 Answers

The class AbstractMap.SimpleEntry is generic and can be useful.

Android programmers could use BasicNameValuePair

Update:

BasicNameValuePair is now deprecated (API 22). Use Pair instead.

Example usage:

Pair<Integer, String> simplePair = new Pair<>(42, "Second"); Integer first = simplePair.first; // 42 String second = simplePair.second; // "Second" 

The Pair class from Commons Lang might help:

Pair<String, String> keyValue = new ImmutablePair("key", "value"); 

Of course, you would need to include commons-lang.

Use of javafx.util.Pair is sufficient for most simple Key-Value pairings of any two types that can be instantiated.

Pair<Integer, String> myPair = new Pair<>(7, "Seven"); Integer key = myPair.getKey(); String value = myPair.getValue(); 

import java.util.Map; public class KeyValue<K, V> implements Map.Entry<K, V> { private K key; private V value; public KeyValue(K key, V value) { this.key = key; this.value = value; } public K getKey() { return this.key; } public V getValue() { return this.value; } public K setKey(K key) { return this.key = key; } public V setValue(V value) { return this.value = value; } } 

I like to use

Properties

Example:

Properties props = new Properties(); props.setProperty("displayName", "Jim Wilson"); // (key, value) String name = props.getProperty("displayName"); // => Jim Wilson String acctNum = props.getProperty("accountNumber"); // => null String nextPosition = props.getProperty("position", "1"); // => 1 

If you are familiar with a hash table you will be pretty familiar with this already

You can create your custom KeyValuePair class easily

public class Key<K, V>{ K key; V value; public Key() { } public Key(K key, V value) { this.key = key; this.value = value; } public void setValue(V value) { this.value = value; } public V getValue() { return value; } public void setKey(K key) { this.key = key; } public K getKey() { return key; } } 

My favorite is

HashMap<Type1, Type2> 

All you have to do is specify the datatype for the key for Type1 and the datatype for the value for Type2. It's the most common key-value object I've seen in Java.

Hashtable<String, Object> 

It is better than java.util.Properties which is by fact an extension of Hashtable<Object, Object>.

I've published a NameValuePair class in GlobalMentor's core library, available in Maven. This is an ongoing project with a long history, so please submit any request for changes or improvements.