Java之通过Class字节码对象获取构造方法创建对象

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/**
 * Class字节码对象获取构造方法创建对象
 * @author 郑清
 */
public class Demo {

	public static void main(String[] args) throws NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
		test();
	}
	
	public static void test() throws NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
		//获取类的字节码对象
		Class cla = Student.class;
		//获取公共(public)的构造方法：
		Constructor constructor = cla.getConstructor(String.class,int.class);
		//上面获得的是带2个参数的构造方法==>所以使用获取的构造方法的时候 也必须写对应的参数     如果不写编译没问题，但运行会报错
		Object newInstance = constructor.newInstance("String类型name",18);
		System.out.println("newInstance："+newInstance);
		
		//获取私有(private)的构造方法
		Constructor declaredConstructor = cla.getDeclaredConstructor(int.class);
		//能获取但不能使用 ==》因为还是会检查权限
		declaredConstructor.setAccessible(true);//忽略权限检查
		Object newInstance2 = declaredConstructor.newInstance(18);
		System.out.println("newInstance2:"+newInstance2);
		System.out.println(newInstance2 instanceof Student);//true
	}

}
class Student {
	public Student() {}
	public Student(String name) {}
	public Student(String name,int age) {}
	private Student(int age) {}
}

运行结果图：