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Class getDeclaredConstructors() method in Java with Examples

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  • Last Updated : 05 Jun, 2021

The getDeclaredConstructors() method of java.lang.Class class is used to get the constructors of this class, which are the constructors that are private, public, protected or default. The method returns the constructors of this class in the form of array of Constructor objects. 
Syntax: 
 

public Constructor[] getDeclaredConstructors()
                      throws SecurityException

Parameter: This method does not accept any parameter.
Return Value: This method returns the constructors of this class in the form of an array of Constructor objects. 
Exception This method throws SecurityException if a security manager is present and the security conditions are not met.
Below programs demonstrate the getDeclaredConstructors() method.
Example 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()));
    }
}

Output: 

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

 

Example 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()));
    }
}

Output: 

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

 

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


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