使用Collections.emptyList();的好处就是能节省内存开销,因为它一直引用同一对象地址而 new ArrayList<>();是生成新的对象(每次当 new 一个对象的时候就会在堆中为它分配一块内存)。 EmptyList 不想让你碰人家,你还强行非礼,那就会~ 歌曲推荐: 陈冠蒲《太多》 如有哪些地方有歧义望指正。分享java开发相关的各...
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(){returnCollec...
当以List<Book> list = new ArrayList<Book>();方式创建ArrayList集合时,不指定集合的大小 1 /** 2 *Constructs an empty list with an initial capacity of ten。意思是:构造一个空数组,默认的容量为10 3 */ 4 public ArrayList() { 5 this.elementData = DEFAULTCAPACITY_EMPTY_ELEMENTDATA; 1. 2. 3....
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...
Code to improve: final Collection<DiscussionTopics> topics =s.getTopics(); final boolean anyTopics= topics !=null&& !topics.isEmpty(); Change to: import org.apache.commons.collections.CollectionUtils; !CollectionUtils.isEmpty(s.getTopics())...
// Returns a stream of all the sublists of its input listpublicclassSubLists{publicstatic<E>Stream<List<E>>of(List<E>list){returnStream.concat(Stream.of(Collections.emptyList()),prefixes(list).flatMap(SubLists::suffixes));}privatestatic<E>Stream<List<E>>prefixes(List<E>list){returnIntSt...
Returns and empty list with this error: SQLiteQuery: SELECT * FROM EVENT_TYPE W/System.err: java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.hashCode()' on a null object reference W/System.err: at com.blabla.Models.Event.EventType.hashCode(EventType.jav...
0.1:8848]) tried: failed to req API:http://127.0.0.1:8848/nacos/v1/ns/instance/list. code:404 msg: service not found: DEFAULT_GROUP@@configurators:org.apache.dubbo.samples.basic.api.DemoService:1.0.0:MyGroup at com.alibaba.nacos.client.naming.net.NamingProxy.reqAPI(NamingProxy.java:380...
publicList<Types>buildTree(List<Types>list){//父级(总的)List<Types>typesList=newArrayList<>();list.forEach(t->{if(t.getParentId()==null||t.getParentId()==0){typesList.add(nodeTree(t,list));}});returntypesList;}//types 父级的对象publicTypesnodeTree(Types types,List<Types>list){Li...
相关搜索:js return返回的值return返回函数Return语句未返回返回结构时“‘return’with a value,in function return void”js return返回值js return 返回值Java - return多个返回类型PHP函数中的多个return语句js中return返回多个值return语句不返回任何内容“return”函数不返回变量pythonReturn not working on empty che...