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 Tools and Libs > Commons Lang3 > Reflection > Invoke Constructor with Types

Invoke Constructor with Types 

Apache Commons Lang 3.0 is a java library with lot of utilities and reusable components. This requires the library commons-lang3-3.0.1.jar to be in classpath. The following example shows using ConstructorUtils.invokeConstructor() API. It returns a new instance by invoking the matching constructor.

File Name  :  
com/bethecoder/tutorials/commons_lang/common/Student.java 
   
package com.bethecoder.tutorials.commons_lang.common;

public class Student extends Person {

  private static String DEFAULT_NAME = "Unknown";
  private String name;
  private int age;
  private String hobby;

  public Student() {
  }

  public Student(String name, int age, String hobby) {
    super();
    this.name = name;
    this.age = age;
    this.hobby = hobby;
  }

  public String getName() {
    return name;
  }
  public void setName(String name) {
    this.name = name;
  }
  public int getAge() {
    return age;
  }
  public void setAge(int age) {
    this.age = age;
  }
  public String getHobby() {
    return hobby;
  }
  public void setHobby(String hobby) {
    this.hobby = hobby;
  }
  
  public String toString() {
    return "Student[name = " + name + ", age = " + age + ", hobby = " + hobby + "]";
  }
}
   

File Name  :  
com/bethecoder/tutorials/commons_lang/tests/reflections/InvokeConstructorWithTypeTest.java 
Author  :  Sudhakar KV
Email  :  kvenkatasudhakar@gmail.com
   
package com.bethecoder.tutorials.commons_lang.tests.reflections;

import java.lang.reflect.InvocationTargetException;

import org.apache.commons.lang3.reflect.ConstructorUtils;

import com.bethecoder.tutorials.commons_lang.common.Student;

public class InvokeConstructorWithTypeTest {

  /**
   @param args
   @throws InstantiationException 
   @throws InvocationTargetException 
   @throws IllegalAccessException 
   @throws NoSuchMethodException 
   */
  public static void main(String[] argsthrows NoSuchMethodException, 
    IllegalAccessException, InvocationTargetException, 
    InstantiationException {

    Student stud = ConstructorUtils.invokeConstructor(
        Student.class, 
        new Object [] { "Sriram"2"Chess" },
        new Class<?> [] { String.class, Integer.class, String.class });
    System.out.println(stud);

    Integer intObj = ConstructorUtils.invokeConstructor(
        Integer.class, new Object [] { "123456" },
        new Class<?> [] { String.class } );
    System.out.println(intObj);
  }

}
   

It gives the following output,
Student[name = Sriram, age = 2, hobby = Chess]
123456


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