Class getConstructor() method in Java with Examples (original) (raw)

Last Updated : 16 Dec, 2019

The getConstructor() method of java.lang.Class class is used to get the specified constructor of this class with the specified parameter type, which is the constructor that is public and its members. The method returns the specified constructor of this class in the form of Constructor object.

Syntax:

public Constructor getConstructor(Class[] parameterType) throws NoSuchMethodException, SecurityException

Parameter: This constructor accepts a parameters parameterType which is the array of parameter type for the specified constructor.

Return Value: This method returns the specified constructor of this class in the form of Constructor objects.

Exception This method throws:

• NoSuchMethodException if a constructor with the specified name is not found.
• NullPointerException if name is null
• SecurityException if a security manager is present and the security conditions are not met.
  Below programs demonstrate the getConstructor() method.
  Example 1:
  import java.util.*;
public class Test {
`public` `Test() {} ` public static void main(String[] args)
`throws` `ClassNotFoundException, NoSuchMethodException ` {
`Class myClass = Class.forName(` `"Test"` `); ` System.out.println( "Class represented by myClass: "
`+ myClass.toString()); ` Class[] parameterType = null ;
`System.out.println( ` "Constructor of myClass: "
`+ myClass.getConstructor(parameterType)); ` }
}
  Output:
  Class represented by myClass: class Test
  Constructor of myClass: public Test()
  Example 2:
  import java.util.*;
class Main {
`private` `Main() {} ` public static void main(String[] args)
`throws` `ClassNotFoundException, NoSuchMethodException ` {
`Class myClass = Class.forName(` `"Main"` `); ` System.out.println( "Class represented by myClass: "
`+ myClass.toString()); ` Class[] parameterType = null ;
`try` `{ ` System.out.println(
`"Constructor of myClass: "` + myClass.getConstructor(parameterType));
`} ` catch (Exception e) {
`System.out.println(e); ` }
  `` }
}
  Output:
  Class represented by myClass: class Main
  java.lang.NoSuchMethodException: Main.()
  Reference: https://docs.oracle.com/javase/9/docs/api/java/lang/Class.html#getConstructor-java.lang.Class…-

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