rspec/rules/S2129/java/rule.adoc

== Why is this an issue?

Calling constructors for `String`, `BigInteger`, `BigDecimal` and the objects used to wrap primitives is less efficient and less clear than relying on autoboxing or `valueOf`.

Consider simplifying when possible for more efficient and cleaner code.

=== Noncompliant code example

[source,java]
----
String empty = new String(); // Noncompliant; yields essentially "", so just use that.
String nonempty = new String("Hello world"); // Noncompliant
Double myDouble = new Double(1.1); // Noncompliant; use valueOf
Integer integer = new Integer(1); // Noncompliant
Boolean bool = new Boolean(true); // Noncompliant
BigInteger bigInteger1 = new BigInteger("3"); // Noncompliant
BigInteger bigInteger2 = new BigInteger("9223372036854775807"); // Noncompliant
BigInteger bigInteger3 = new BigInteger("111222333444555666777888999"); // Compliant, greater than Long.MAX_VALUE
BigDecimal bigDecimal = new BigDecimal("42.0"); // Compliant (see Exceptions section)
----


=== Compliant solution

[source,java]
----
String empty = "";
String nonempty = "Hello world";
Double myDouble = 1.1;
Integer integer = 1;
Boolean bool = true;
BigInteger bigInteger1 = BigInteger.valueOf(3);
BigInteger bigInteger2 = BigInteger.valueOf(9223372036854775807L);
BigInteger bigInteger3 = new BigInteger("111222333444555666777888999");
BigDecimal bigDecimal = new BigDecimal("42.0");
----


=== Exceptions

`BigDecimal` constructor with `double` argument is ignored as using `valueOf` instead might change resulting value.
See S2111.


== Resources

* https://docs.oracle.com/javase/tutorial/java/data/autoboxing.html[Oracle - Learning the Java Language] - Autoboxing and Unboxing


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'''
== Implementation Specification
(visible only on this page)

=== Message

Remove this "xxx" constructor


'''
== Comments And Links
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=== relates to: S1533

=== on 10 Oct 2014, 14:03:24 Freddy Mallet wrote:
@Ann, my 2 cents:

* I would not activate this rule by default
* Would slightly update the title like this : Constructors should not be used to instanciate new String or primitive wrappers.

=== on 13 Oct 2014, 12:40:40 Ann Campbell wrote:
What do you think [~nicolas.peru]? Active by default or not?

=== on 13 Oct 2014, 12:52:34 Nicolas Peru wrote:
IMO : Activated by default but with a low severity : minor to trivial this is really easy to fix and should not clutter you too much to focus on real trouble but should still be reported to be dealt with.

=== on 14 Jul 2016, 16:08:20 Ann Campbell wrote:
https://github.com/google/error-prone/blob/master/docs/bugpattern/BoxedPrimitiveConstructor.md

endif::env-github,rspecator-view[]