返回不可变列表而不是可变列表的原因是什么?
Given below is the excerpt from Oracle JDK 9 Documentation :
For optimal performance, the immutable collections store a data set that never changes. However, you may be able to take advantage of the performance and space-saving benefits even if your data is subject to change. These collections may provide better performance than the mutable collections, even if your data changes occasionally.
List#of
are static factory methods which provide a convenient way to create immutable lists. In other words, it's a convenience method to create immutable lists. Prior to Java-9, this was possible through separate APIs like Collections#unmodifiableList
.
If you want to get a mutable list, you can instantiate an ArrayList
with this immutable list as the parameter.
import java.util.ArrayList;
import java.util.List;
public class Main {
public static void main(String[] args) {
List<String> mutableList = new ArrayList<>(List.of("A", "B", "C"));
mutableList.add("D");
System.out.println(mutableList);
}
}
Output:
[A, B, C, D]
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