What is autoboxing and unboxing in java ?

Java automatically convert primitive types in to corresponding wrapper class is called autoboxing and converting wrapper class in to primitive types called unboxing. This feature introduced in java 1.5

 

 

Example

 

package com.vinod.test;

import java.util.ArrayList;
import java.util.List;

public class AutoBoxing {

    public static void main(String[] args) {
        List<Integer> list = new ArrayList();
        list.add(1); // Autoboxing
        list.add(2);
        int a = list.get(0);// unboxing
        int b = list.get(1);
        System.out.println("value of a " + a + "value of b" + b);

    }

}
 

Spring Core- Creating beans example

 

There are two ways we can create beans spring

1.XML Based
Create xml configuration for denfining beans
2.Annotation based
Create annotation based java configuration class to create beans

Note: In this example creating beans for a simple Student object
1. XML Based configuration

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
    <bean id="studentBean" class="com.vinod.test.Student">
    </bean>
</beans>

2. Annotation based configuration

package com.vinod.test;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class SpringCoreConfig {
    @Bean
    public Student getStudentBean() {
        Student stud = new Student();
        stud.setName("Vinod");
        return stud;
    }
}

3. Student.java

package com.vinod.test;

public class Student {
    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

3. Test class

package com.vinod.test;

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SpringCoreMain {

    public static void main(String[] args) {

        // Getting beans from XML based bean configuration
        ApplicationContext context = new ClassPathXmlApplicationContext("spring-core.xml");
        // Student bean
        Student obj = (Student) context.getBean("studentBean");
        obj.setName("vinod");
        System.out.println(obj.getName());

        // Getting beans from Annotaion based configuration

        AnnotationConfigApplicationContext anno = new AnnotationConfigApplicationContext();
        anno.register(SpringCoreConfig.class);
        anno.refresh();
        Student stu = anno.getBean(Student.class);
        System.out.println(stu.getName());
    }

}

4. Output

vinod

Vinod

5. Download examples
https://github.com/kkvinodkumaran/spring