81 lines
2.1 KiB
Plaintext
81 lines
2.1 KiB
Plaintext
== Why is this an issue?
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The purpose of the `hashCode` method is to return a hash code based on the contents of the object.
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Similarly, the purpose of the `toString`
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method is to provide a textual representation of the object's contents.
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Calling `hashCode()` and `toString()` directly on array instances should be avoided because the default implementations provided by the `Object` class do not provide meaningful results for arrays.
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`hashCode()` returns the array's "identity hash code", and `toString()` returns nearly the same value.
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Neither method's output reflects the array's contents.
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== How to fix it
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Use relevant static `Arrays` method.
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* `Arrays.hashCode` or `Arrays.deepHashCode`
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* `Arrays.toString` or `Arrays.deepToString`
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=== Code examples
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==== Noncompliant code example
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[source,java,diff-id=1,diff-type=noncompliant]
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----
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public static void main(String[] args) {
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String argStr = args.toString(); // Noncompliant
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int argHash = args.hashCode(); // Noncompliant
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}
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----
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==== Compliant solution
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[source,java,diff-id=1,diff-type=compliant]
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----
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public static void main(String[] args) {
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String argStr = Arrays.toString(args); // Compliant
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int argHash = Arrays.hashCode(args); // Compliant
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}
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----
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== Resources
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=== Documentation
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* https://docs.oracle.com/en/java/javase/20/docs/api/java.base/java/util/Arrays.html[Oracle Java SE - Arrays API]
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=== Articles & blog posts
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* https://github.com/google/error-prone/blob/master/docs/bugpattern/ArrayHashCode.md[Error Prone - ArrayHashCode]
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ifdef::env-github,rspecator-view[]
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'''
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== Implementation Specification
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(visible only on this page)
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=== Message
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* Use "Arrays.hashCode(array)" instead.
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* Use "Arrays.toString(array)" instead.
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'''
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== Comments And Links
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(visible only on this page)
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=== on 10 Oct 2014, 15:25:37 Freddy Mallet wrote:
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My 2 cents @Ann:
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* I would prefer a rule title like "hashCode" and "toString" methods should never be called on array instances
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* I would increase the severity to "Critical"
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=== on 15 Jul 2016, 14:24:30 Ann Campbell wrote:
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https://github.com/google/error-prone/blob/master/docs/bugpattern/ArrayHashCode.md
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endif::env-github,rspecator-view[]
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