JAVA EXAMPLE PROGRAMS

JAVA EXAMPLE PROGRAMS

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Method Reference - Reference to a Instance Method example.


This example shows how to use Method Reference feature on instance method:

package com.java2novice.methodreference;

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

import com.java2novice.lambda.Employee;

public class InstanceMethodReferenceEx {

	public static void main(String a[]) {

		List<Employee> empList = new ArrayList<>();
		empList.add(new Employee("Nataraja G", "Accounts", 8000));
		empList.add(new Employee("Nagesh Y", "Admin", 15000));
		empList.add(new Employee("Vasu V", "Security", 2500));
		empList.add(new Employee("Amar", "Entertinment", 8500));

		MyExampComparator comp = new MyExampComparator();

		// sort it in method reference way
		System.out.println("<--- Sorted list with Method Reference --->");
		Collections.sort(empList, comp::compare);
		empList.forEach(System.out::println);

		// sort it in lambda expression way
		System.out.println("\n\n<--- Sorted list with Lambda expression --->");
		Collections.sort(empList, (emp1, emp2) -> comp.compare(emp1, emp2));
		empList.forEach(System.out::println);
	}
}

Here is MyExampComparator class:

package com.java2novice.methodreference;

import com.java2novice.lambda.Employee;

public class MyExampComparator {

	public int compare(Employee emp1, Employee emp2) {

		return emp1.getSalary().compareTo(emp2.getSalary());
	}
}

Here is Employee POJO class:

package com.java2novice.lambda;

public class Employee {

	private String name;
	private String account;
	private Integer salary;

	public Employee(String name, String account, Integer salary) {
		super();
		this.name = name;
		this.account = account;
		this.salary = salary;
	}

	@Override
	public String toString() {

		return "name: "+ this.name +" | account: "+ this.account +" | salary: "+this.salary;
	}

	public String getName() {
		return name;
	}

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

	public String getAccount() {
		return account;
	}

	public void setAccount(String account) {
		this.account = account;
	}

	public Integer getSalary() {
		return salary;
	}

	public void setSalary(Integer salary) {
		this.salary = salary;
	}
}

Output:
<--- Sorted list with Method Reference --->
name: Vasu V | account: Security | salary: 2500
name: Nataraja G | account: Accounts | salary: 8000
name: Amar | account: Entertinment | salary: 8500
name: Nagesh Y | account: Admin | salary: 15000


<--- Sorted list with Lambda expression --->
name: Vasu V | account: Security | salary: 2500
name: Nataraja G | account: Accounts | salary: 8000
name: Amar | account: Entertinment | salary: 8500
name: Nagesh Y | account: Admin | salary: 15000
<< Previous Program | Next Program >>

Java-8 Method References Examples

  1. Method Reference - Reference to a Static Method example.
  2. Method Reference - Reference to a Instance Method example.
  3. Method Reference - Reference to a Constructor example.
Knowledge Centre
Procedural Vs Object-oriented Programs
In procedural program, programming logic follows certain procedures and the instructions are executed one after another. In OOP program, unit of program is object, which is nothing but combination of data and code.

In procedural program, data is exposed to the whole program whereas in OOPs program, it is accessible with in the object and which in turn assures the security of the code.
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About Author

I'm Nataraja Gootooru, programmer by profession and passionate about technologies. All examples given here are as simple as possible to help beginners. The source code is compiled and tested in my dev environment.

If you come across any mistakes or bugs, please email me to [email protected].

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Reference: Java™ Platform Standard Ed. 7 - API Specification | Java™ Platform Standard Ed. 8 - API Specification | Java is registered trademark of Oracle.
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