package com.test.lambda.day03.exer;

//交易员类
public class Trader {

private String name;
private String city;

public Trader() {
}

public Trader(String name, String city) {
	this.name = name;
	this.city = city;
}

public String getName() {
	return name;
}

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

public String getCity() {
	return city;
}

public void setCity(String city) {
	this.city = city;
}

@Override
public String toString() {
	return "Trader [name=" + name + ", city=" + city + "]";
}

}

package com.test.lambda.day03.exer;

//交易类
public class Transaction {

	private Trader trader;
	private int year;
	private int value;

	public Transaction() {
	}

	public Transaction(Trader trader, int year, int value) {
		this.trader = trader;
		this.year = year;
		this.value = value;
	}

	public Trader getTrader() {
		return trader;
	}

	public void setTrader(Trader trader) {
		this.trader = trader;
	}

	public int getYear() {
		return year;
	}

	public void setYear(int year) {
		this.year = year;
	}

	public int getValue() {
		return value;
	}

	public void setValue(int value) {
		this.value = value;
	}

	@Override
	public String toString() {
		return "Transaction [trader=" + trader + ", year=" + year + ", value="
				+ value + "]";
	}

}


package com.test.lambda.day03.exer;

import java.util.*;
import java.util.stream.Stream;
import org.junit.Before;
import org.junit.Test;

public class TestTransaction {
	
	List<Transaction> transactions = null;
	
	@Before
	public void before(){
		Trader raoul = new Trader("Raoul", "Cambridge");
		Trader mario = new Trader("Mario", "Milan");
		Trader alan = new Trader("Alan", "Cambridge");
		Trader brian = new Trader("Brian", "Cambridge");
		
		transactions = Arrays.asList(
				new Transaction(brian, 2011, 300),
				new Transaction(raoul, 2012, 1000),
				new Transaction(raoul, 2011, 400),
				new Transaction(mario, 2012, 710),
				new Transaction(mario, 2012, 700),
				new Transaction(alan, 2012, 950)
		);
	}
	
	//1. 查找所有来自剑桥的交易员，并按姓名排序
	@Test
	public void test1(){
		transactions.stream()
					.filter((t) -> t.getTrader().getCity().equals("Cambridge"))
					.map(Transaction::getTrader)
					//.sorted((t1, t2) -> t1.getName().compareTo(t2.getName()))
					.sorted(Comparator.comparing(Trader::getName))
					.distinct()
					.forEach(System.out::println);
	}
}

请问TestTransaction 类中的test1()方法，map(Transaction::getTrader)里面直接用的是Transaction::getTrader（类名::实例方法名），为什么可以这样写？不应该是 类名::静态方法名 这种格式吗？
我之前这这样用的：
package com.test.lambda.day01;

public class Employee {

    private int id;
    private String name;
    private Integer age;
    private double salary;
    private Status status;

    public Employee() {
    }

    public Employee(String name) {
        this.name = name;
    }

    public Employee(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public Employee(int id, String name, int age, double salary) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.salary = salary;
    }

    public Employee(int id, String name, int age, double salary, Status status) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.salary = salary;
        this.status = status;
    }

    public Employee(Integer integer) {
    }

    public Employee(Integer integer, Integer integer1) {
    }

    public Status getStatus() {
        return status;
    }

    public void setStatus(Status status) {
        this.status = status;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public Integer getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public double getSalary() {
        return salary;
    }

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

    public String show() {
        return "测试方法引用！";
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + age;
        result = prime * result + id;
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        long temp;
        temp = Double.doubleToLongBits(salary);
        result = prime * result + (int) (temp ^ (temp >>> 32));
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Employee other = (Employee) obj;
        if (age != other.age)
            return false;
        if (id != other.id)
            return false;
        if (name == null) {
            if (other.name != null)
                return false;
        } else if (!name.equals(other.name))
            return false;
        if (Double.doubleToLongBits(salary) != Double.doubleToLongBits(other.salary))
            return false;
        return true;
    }

    @Override
    public String toString() {
        return "Employee [id=" + id + ", name=" + name + ", age=" + age + ", salary=" + salary + ", status=" + status
                + "]";
    }

    public enum Status {
        FREE, BUSY, VOCATION;
    }

}


@Test
    public void test2(){
        Employee emp = new Employee();
        emp.setAge(12);
        Supplier<Integer> sup2 = emp :: getAge;
        Integer num = sup2.get();
        System.out.println(num);
    }
这里就是先new出来实例对象Employee emp = new Employee();  然后再 emp :: getAge的。
请问这两个的区别是什么？