所以可定义成static final(对于数组)或者Collections.emptyList()/emptyMap()/emptySet()来公用同一个对象,减少性能影响。 代码2: 1//The right way to return an array from a collection 2privatefinalList<Cheese> cheesesInStock = ...; 3privatestaticfinalCheese[] EMPTY_CHEESE_ARRAY =newCheese[0]; 4...
A collection-valued method can be made to return the same immutable empty collection every time it needs to return an empty collection. /** * The right way to return a copy of a collection * @return an array containing all of the cheeses in the shop. */ public List<Cheese> getCheeseL...
下面是一个示例代码,演示了如何在Java中返回一个空的列表: importjava.util.Collections;importjava.util.List;publicclassEmptyListDemo{publicstaticvoidmain(String[]args){List<String>emptyList=getEmptyList();System.out.println("Empty List: "+emptyList);}publicstaticList<String>getEmptyList(){returnColle...
The PR #3097 would now return true for all Optional.isEmpty() classes when using RETURNS_DEEP_STUBS and will return a real Optional also in the RETURNS_DEEP_STUBS, as discussen with @TimvdLippe in the PR. The behavior of Collection.isEmpty() remains the same. AndreasTu added a commit ...
Effective Java2读书笔记 1. It is errorprone to returnnullin place of an empty (zero-length) array or collection. Because the programmer writing the client might forget to write the special case code to handle anullreturn. 2. It is possible to return the same zero-length array from every...
提供的API服务对这两种情况都需要考虑。Collection接口既是Iterable的子类又包含stream方法,所以这种类型可以同时满足上面两种情况。如何返回的数据不大,可以使用ArrayList或HashSet直接返回。 如果返回的数据过大,但可以简明地进行表达,可以返回特殊的集合。例如返回一个指定Set的幂Set:如果Set包含n个元素,对应的幂Set包含...
For methods that return a set of values using an array or collection, returning an empty array or collection is an excellent alternative to returning a null value, as most callers are better equipped to handle an empty set than a null value....
After we ran the program, it printed the length of the empty array, which is 0. Return an Empty Array Using Empty Curly Braces in Java Empty curly braces,{ }, in Java, represent an empty array or collection. When used in the context of array initialization, it denotes an array with ...
Collections.emptySet() is an immutable type-safe collection. You don't want to use that if you intend on adding elements. Further, being a Collection it wouldn't have the extended features of a List even if you could add to it.
Code to improve: final Collection<DiscussionTopics> topics = s.getTopics(); final boolean anyTopics = topics != null && !topics.isEmpty(); Change to: apache java 转载 mob604756f8c81a 2021-01-05 17:05:00 147阅读 2评论 java if后面return java if return 在java里面return有三种用法:...