63 lines
2.0 KiB
Plaintext
63 lines
2.0 KiB
Plaintext
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== Why is this an issue?
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Java 21 introduces a new SequencedCollection interface that provides a uniform API for accessing its first and last elements.
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The new `getFirst()` and `getLast()` methods offer a consistent way to access elements across `SortedSet`, `NavigableSet`, `LinkedHashSet`, `List` and `Deque` collections.
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Because those methods are more concise and readable, they should be used instead of more complex workarounds that recreate the same behavior.
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For example, `list.get(list.size() - 1)` can be replaced by `list.getLast()`.
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This rule identifies code that can be simplified by using the new `getFirst()` and `getLast()` methods.
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== How to fix it
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Replace the highlighted code with the corresponding `getFirst()` or `getLast()` methods.
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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 String concatenateFirstAndLast(List<String> list) {
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return list.get(0) + // Noncompliant
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list.get(list.size() - 1); // 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 String concatenateFirstAndLast(List<String> list) {
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return list.getFirst() + // Compliant
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list.getLast(); // Compliant
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}
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----
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==== Noncompliant code example
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[source,java,diff-id=2,diff-type=noncompliant]
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----
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public String concatenateFirstAndLast(LinkedHashSet<String> linkedHashSet) {
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return linkedHashSet.iterator().next() + // Noncompliant
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new ArrayList(linkedHashSet).get(linkedHashSet.size() - 1); // Noncompliant
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}
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----
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==== Compliant solution
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[source,java,diff-id=2,diff-type=compliant]
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----
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public String concatenateFirstAndLast(LinkedHashSet<String> linkedHashSet) {
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return linkedHashSet.getFirst() + // Compliant
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linkedHashSet.getLast(); // Compliant
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}
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----
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== Resources
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=== Documentation
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* https://openjdk.org/jeps/431[JEP 431: Sequenced Collections]
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* https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/SequencedCollection.html[Java SE 21 API documentation - SequencedCollection]
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