How Can I Efficiently Convert a Java List to a Map Using Streams and Lambdas?

Converting Java List to Map with Java 8 Streams and Lambdas

Background:

Converting a list of objects to a map is a common task. Java 7 and below require imperative coding using a for-each loop. In Java 8, using streams and lambdas provides a concise and elegant solution.

Java 7 Solution:

private Map<string choice> nameMap(List<choice> choices) {
    final Map<string choice> hashMap = new HashMap();
    for (final Choice choice : choices) {
        hashMap.put(choice.getName(), choice);
    }
    return hashMap;
}</string></choice></string>

Java 8 Solution Without Guava:

Leveraging the Collectors class, the conversion can be done in a single stream operation:

Map<string choice> result =
    choices.stream().collect(Collectors.toMap(Choice::getName,
                                              Function.identity()));</string>

Here, Choice::getName retrieves the name key, and Function.identity() preserves the value.

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