Java中的类 getDeclaredConstructors() 方法和示例

Java.lang.Class 类的getDeclaredConstructors()方法用于获取该类的构造函数，即私有、公有、受保护或默认的构造函数。该方法以 Constructor 对象数组的形式返回该类的构造函数。
句法：

public Constructor[] getDeclaredConstructors()
                      throws SecurityException

参数：此方法不接受任何参数。
返回值：该方法以Constructor对象数组的形式返回该类的构造函数。
异常如果存在安全管理器并且不满足安全条件，则此方法将引发SecurityException 。
下面的程序演示了 getDeclaredConstructors() 方法。
示例 1：

Java

// Java program to demonstrate
// getDeclaredConstructors() method
 
import java.util.*;
 
public class Test {
    public static void main(String[] args)
        throws ClassNotFoundException
    {
 
        // returns the Class object for this class
        Class myClass = Class.forName("Test");
 
        System.out.println("Class represented by myClass: "
                           + myClass.toString());
 
        // Get the constructors of myClass
        // using getDeclaredConstructors() method
        System.out.println(
            "DeclaredConstructors of myClass: "
            + Arrays.toString(
                  myClass.getDeclaredConstructors()));
    }
}

输出：

Class represented by myClass: class Test
DeclaredConstructors of myClass: [public Test()]

示例 2：

Java

// Java program to demonstrate
//getDeclaredConstructors() method
 
import java.util.*;
 
class Main {
 
    public Object obj;
 
    private Main()
    {
 
        class Arr {
        };
 
        obj = new Arr();
    }
 
    public static void main(String[] args)
        throws ClassNotFoundException
    {
        // returns the Class object for this class
        Class myClass = Class.forName("Main");
 
        System.out.println("Class represented by myClass: "
                           + myClass.toString());
 
        // Get the constructors of myClass
        // using getDeclaredConstructors() method
        System.out.println(
            "DeclaredConstructors of myClass: "
            + Arrays.toString(
                  myClass.getDeclaredConstructors()));
    }
}

输出：

Class represented by myClass: class Main
DeclaredConstructors of myClass: [private Main()]

参考： https://docs.oracle.com/javase/9/docs/api/ Java/lang/Class.html#getDeclaredConstructors–