在Java中,List是一种常见的集合类型,常用来存储一组元素。而在对List进行操作时,我们经常需要判断它是否为空。此时,就可以使用List提供的isEmpty()方法来判断List是否为空。List isEmpty()方法List接口是Collection接口的子接口,因此,List中也包含了Collection的一些基本方法,比如size、contains、add等。而List中的is...
publicbooleanisEmpty(){returnsize==0;} Java Copy 示例: ArrayList<String>list1=newArrayList<>();list1.add("Apple");list1.add("Banana");ArrayList<String>list2=newArrayList<>();System.out.println(list1.isEmpty());// 输出 falseSystem.out.println(list2.isEmpty());// 输出 true Java Copy ...
// isEmpty() method in ArrayList // for ArrayList functions importjava.util.ArrayList; publicclassGFG{ publicstaticvoidmain(String[]args) { // creating an Empty Integer ArrayList ArrayList<Integer>arr=newArrayList<Integer>(10); // check if the list is empty or not using function booleanans=a...
import java.util.Vector; public class Main { public static void main(String[] args) { List l=new Vector(); int i=0; for(i=0;i<10000;i++){ l.add(new Integer(i).toString()); } System.out.println(i); Long sTime=System.nanoTime(); l.size(); Long eTime=System.nanoTime(); ...
看一下isEmpty() isEmpty...,list是一个空集合,而不是null,否则会抛异常。 所有我们在判断集合不为空的时候常采用:if(list!=null&&!list.isEmpty())的方法去取list里面的值 Java-集合(list接口) ); list.addAll(set); System.out.println(list);//[0,1,2,3,8] isEmpty()判断集合是否为空 ...
技术标签:Javajavaspring boot 在进行集合判空时,能用Collection.isEmpty(testList)的就不要用testList.size(),isEmpty不仅可以判断集合是否为null,在时间复杂度上也更优秀。 sonar规范这样描述: Collection.isEmpty() should be used to test for emptiness Using Collection.size() to test f... ...
Java Optional isPresent and isEmpty Introduction In Java, theOptionalclass was introduced in Java 8 as a container object that may or may not contain a non-null value. It is designed to handle scenarios where a value may be present or absent, avoiding the need for null checks. TheisPresent...
personList.forEach(OptionalDemo::introduceChinese); // 输出:I'm from China. System.out.println(inWhichCountryUppercase(lucy)); // 输出:Exception in thread "main" java.util.NoSuchElementException // at java.util.Optional.orElseThrow(Optional.java:290) ...
import java.util.List; import java.util.Vector; public class Main { public static void main(String[] args) { List l=new Vector(); int i=0; for(i=0;i<10000;i++){ l.add(new Integer(i).toString()); } System.out.println(i); Long sTime=System.nanoTime(); l.size(); Long ...
isEmpty()) return EMPTY_SUBSET; else return new RDFPlainLiteralPatternValueSpaceSubset(difference); } else { RDFPlainLiteralLengthInterval[] intervals=getIntervalsFor(datatypeRestriction); if (intervals[0]==null && intervals[1]==null) return valueSpaceSubset; else { List<RDFPlainLiteralLength...