From effective Java 3rd Edition

factory.method.instead.of.constructors.md

Static factory methods instead of constructors

Source: Effective Java 3rd. Edition

Common names for static factory methods

from—type

A conversion method that takes a single parameter and returns a corresponding instance of this type, for example:

Date d = Date.from(instant);

of

An aggregation method that takes multiple parameters and returns an instance of this type that incorporates them, for example:

Set<Rank> faceCards = EnumSet.of(JACK, QUEEN, KING);

valueOf

A more verbose alternative to from and of, for example:

BigInteger prime = BigInteger.valueOf(Integer.MAX_VALUE);

instance or getInstance

Returns an instance that is described by its parameters (if any) but cannot be said to have the same value, for example:

StackWalker luke = StackWalker.getInstance(options);

create or newInstance

Like instance or getInstance, except that the method guarantees that each call returns a new instance, for example:

Object newArray = Array.newInstance(classObject, arrayLen);

getType

Like getInstance, but used if the factory method is in a different class. Type is the type of object returned by the factory method, for example:

FileStore fs = Files.getFileStore(path);

newType

Like newInstance, but used if the factory method is in a different class. Type is the type of object returned by the factory method, for example:

BufferedReader br = Files.newBufferedReader(path);

type

A concise alternative to getType and newType, for example:

List<Complaint> litany = Collections.list(legacyLitany);

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Jaziel Lopez, Software Engineer, TJ Area, BC. MX

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