ToArray( ) 把List内的元素拷贝到一个新的数组内 trimToSize( ) 将容量设置为List中元素的实际数目 三、List的用法 1、List的基础、常用方法: (1)、声明: ①、List<T> mList = new List<T>(); T为列表中元素类型,现在以string类型作为例子 List<string> mList = new List<
publicclassListSortExample{publicstaticvoidmain(String[]args){// 创建并初始化 ListList<Person>list=newArrayList<Person>(){{add(newPerson(1,30,"北京"));add(newPerson(2,20,"西安"));add(newPerson(3,40,"上海"));}};// 使用 Comparable 自定的规则进行排序Collections.sort(list);// 打印 list...
Java can help reduce costs, drive innovation, & improve application services; the #1 programming language for IoT, enterprise architecture, and cloud computing.
下面是一个示例代码,演示了如何获取List的泛型class: importjava.lang.reflect.ParameterizedType;importjava.lang.reflect.Type;importjava.util.ArrayList;importjava.util.List;publicclassGenericClassExample{publicstaticvoidmain(String[]args){List<String>list=newArrayList<>();Class<?>clazz=getGenericTypeClass(list...
public class VirtualThreadTest { static List<Integer> list = new ArrayList<>(); public static void main(String[] args) { // 开启线程 统计平台线程数 ScheduledExecutorService scheduledExecutorService = Executors.newScheduledThreadPool(1); scheduledExecutorService.scheduleAtFixedRate(() -> ...
package javax.crypto;public class DecapsulateException extends GeneralSecurityException;public final class KEM { public static KEM getInstance(String alg) throws NoSuchAlgorithmException; public static KEM getInstance(String alg, Provider p) throws NoSuchAlgorithmException; public static KEM g...
publicclassVirtualThreadExample{ publicstaticvoidmain(String[]args){ ExecutorServiceexecutor=Executors.newVirtualThreadPerTaskExecutor(); executor.submit(()->{ System.out.println(Thread.currentThread().getName()) }); executor.shutdown(); }
*/publicclassArrayList<E>extendsAbstractList<E>implementsList<E>, RandomAccess, Cloneable, java.io.Serializable{privatestaticfinallongserialVersionUID = 8683452581122892189L;/*** 默认容量*/privatestaticfinalintDEFAULT_CAPACITY = 10;/*** 空实例共享的空数组* todo 为什么要区分 EMPTY_ELEMENTDATA 与 ...
Java(21):泛型 packagezzz;importjava.util.ArrayList;importjava.util.List;importjava.util.Random;importjavax.sound.midi.VoiceStatus;importcom.sun.org.apache.xpath.internal.operations.String;publicclassGenericsDemo {publicstaticvoidmain(String[] args) {...
.collect(Collectors.toList()); ``` 2.3Optional(空指针防护盾) ```java // 以前可能会写出这种危险代码 String version = computer.getSoundcard().getUSB().getVersion(); // 现在可以这样写(妈妈再也不用担心NPE了!) String version = computer.flatMap(Computer::getSoundcard) ...