2.3.2Constructor类用于创建对象的方法
// Student类同上一个示例,这里就不在重复提供了
public class ReflectDemo2 {
public static void main(String[] args) throws ClassNotFoundException,
NoSuchMethodException, IllegalAccessException, InvocationTargetException,
InstantiationException {
//T newInstance(Object... initargs):根据指定的构造方法创建对象
//method1();
//method2();
//method3();
//method4();
}
private static void method4() throws ClassNotFoundException, NoSuchMethodException,
InstantiationException, IllegalAccessException, InvocationTargetException {
//获取一个私有的构造方法并创建对象
//1.获取class对象
Class clazz = Class.forName("com.itheima.myreflect3.Student");
//2.获取一个私有化的构造方法.
Constructor constructor = clazz.getDeclaredConstructor(String.class);
//被private修饰的成员,不能直接使用的
//如果用反射强行获取并使用,需要临时取消访问检查
constructor.setAccessible(true);
//3.直接创建对象
Student student = (Student) constructor.newInstance("zhangsan");
System.out.println(student);
}
private static void method3() throws ClassNotFoundException, InstantiationException,
IllegalAccessException {
//简写格式
//1.获取class对象
Class clazz = Class.forName("com.itheima.myreflect3.Student");
//2.在Class类中,有一个newInstance方法,可以利用空参直接创建一个对象
Student student = (Student) clazz.newInstance();//这个方法现在已经过时了,了解一下
System.out.println(student);
}
private static void method2() throws ClassNotFoundException, NoSuchMethodException,
InstantiationException, IllegalAccessException, InvocationTargetException {
//1.获取class对象
Class clazz = Class.forName("com.itheima.myreflect3.Student");
//2.获取构造方法对象
Constructor constructor = clazz.getConstructor();
//3.利用空参来创建Student的对象
Student student = (Student) constructor.newInstance();
System.out.println(student);
}
private static void method1() throws ClassNotFoundException, NoSuchMethodException,
InstantiationException, IllegalAccessException, InvocationTargetException {
//1.获取class对象
Class clazz = Class.forName("com.itheima.myreflect3.Student");
//2.获取构造方法对象
Constructor constructor = clazz.getConstructor(String.class, int.class);
//3.利用newInstance创建Student的对象
Student student = (Student) constructor.newInstance("zhangsan", 23);
System.out.println(student);
}
}
2.3.3小结
获取class对象
三种方式: Class.forName(“全类名”), 类名.class, 对象名.getClass()
获取里面的构造方法对象
getConstructor (Class<?>... parameterTypes) getDeclaredConstructor (Class<?>... parameterTypes)
如果是public的,直接创建对象
newInstance(Object... initargs)
如果是非public的,需要临时取消检查,然后再创建对象
setAccessible(boolean) 暴力反射
页面更新:2024-06-19
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