Method Reference - Reference to a Instance Method example.

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);
	}
}

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());
	}
}

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;
	}
}

<--- 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