importjava.util.ArrayList;importjava.util.List;publicclassMain{publicstaticvoidmain(String[]args){List<String>stringList=newArrayList<>();stringList.add("Java");stringList.add("List");Class<?>elementClass=stringList.get(0).getClass();System.out.println("Class of elements in the list (using ...
AnnotatedElement {2privatestaticfinalintANNOTATION= 0x00002000;3privatestaticfinalintENUM = 0x00004000;4privatestaticfinalintSYNTHETIC = 0x00001000;56privatestaticnativevoidregisterNatives();7static{8registerNatives();9}1011/*12* Private constructor. Only the Java Virtual Machine creates Class objects.(...
You can create multiple objects of one class: Example Create two objects ofMain: publicclassMain{intx=5;publicstaticvoidmain(String[]args){MainmyObj1=newMain();// Object 1MainmyObj2=newMain();// Object 2System.out.println(myObj1.x);System.out.println(myObj2.x);}} ...
Reverses the order of the elements in the specified list. ReverseOrder() Returns a comparator that imposes the reverse of the natural ordering on a collection of objects that implement the Comparable interface. ReverseOrder(IComparator) Returns a comparator that imposes the reverse ordering of th...
Class<ArrayList> arrayListClass = ArrayList.class;Fieldfield=arrayListClass.getDeclaredField("elementData"); field.setAccessible(true); Object[] objects = (Object[]) field.get(arrayList);returnobjects.length; } forEach 方法遍历集合# 不要在使用forEach的同时使用remove和add方法, 不然会报异常. ...
下面我们来看一下 AbstractList 类,它继承了 AbstractCollection 类,同时也是 ArrayList 等具体集合类的父类。先来看一下官方的说明: This class provides a skeletal implementation of the List interface to minimize the effort required to implement this interface backed by a “random access” data store (su...
List<Objects>示例代码 为了更好地理解List<Objects>的初始化和赋值,下面提供一个完整的示例代码: importjava.util.ArrayList;importjava.util.List;publicclassListExample{publicstaticvoidmain(String[]args){List<Objects>list=newArrayList<>();list.add("Hello");list.add(123);list.add(true);list.add(3.14...
add("banana"); list.add("orange"); int index = list.indexOf("banana"); // 返回指定元素在列表中第一次出现的索引 System.out.println(index); // 输出:1 int lastIndex = list.lastIndexOf("banana"); // 返回指定元素在列表中最后一次出现的索引 System.out.println(lastIndex); // 输出:1...
...));// 编译正确 // Object 是 Number 的父类 list.add(new Object());// 编译错误 } } 这里奇怪的地方出现了,为什么和ArrayList...> 集合中取出的元素,也只能赋值给 Object 对象,不然会产生ClassCastException 异常(原因可以结合上界和下界通配符理解) 3.与<?
// 1.获取所有声明的字段 Field[] declaredFieldList = studentClass.getDeclaredFields(); for (Field declaredField : declaredFieldList) { System.out.println("declared Field: " + declaredField); } // 2.获取所有公有的字段 Field[] fieldList = studentClass.getFields(); for (Field field : fiel...