lambda表达式与函数式接口

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

class Ticket{
    private int ticket = 30;

    Lock lock = new ReentrantLock();

    public void sale(){
        lock.lock();
        try {
            if (ticket > 0){
                System.out.println(Thread.currentThread().getName()+"\t卖出了第"+ ticket-- +"张票"+"\t还剩"+ticket+"张票");
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            lock.unlock();
        }
    }
}

public class Dugu {
    public static void main(String[] args) {
        final Ticket ticket = new Ticket();

        new Thread(() -> {for (int i = 0; i < 40; i++) ticket.sale();},"A").start();
        new Thread(() -> {for (int i = 0; i < 40; i++) ticket.sale();},"B").start();
        new Thread(() -> {for (int i = 0; i < 40; i++) ticket.sale();},"C").start();
//        sout
//        new Thread(new Runnable() {
//            public void run() {
//                for (int i = 0; i < 40; i++) {
//                    ticket.sale();
//                }
//            }
//        }, "C").start();
//        new Thread(new Runnable() {
//            public void run() {
//                for (int i = 0; i < 40; i++) {
//                    ticket.sale();
//                }
//            }
//        }, "B").start();
//        new Thread(new Runnable() {
//            public void run() {
//                for (int i = 0; i < 40; i++) {
//                    ticket.sale();
//                }
//            }
//        }, "A").start();
    }
}

//@FunctionalInterface //该注解代表函数式接口，如果符合函数式接口的表达，可以不加
interface Foo{
    //如果式函数式接口，普通方法只能定义一个，否则lambda无法找到默认方法
    public int add(int x, int y);

    //default方法可以随便加，数量不限，只要实现接口类，即便初始值被默认函数设置也无妨
    default int mul(int x, int y){
        return x * y;
    }

    //static方法不影响函数式接口，与静态变量相同，调用不需要实现类
    public static int div(int x, int y){
        return x/y;
    }
}


public class LambdaTest {
    public static void main(String[] args) {
        Foo foo = (int x, int y) -> {
            System.out.println("come in add method");
            return x + y;
        };
        System.out.println(foo.add(3,9));

        System.out.println(foo.mul(4,8));

        System.out.println(Foo.div(18,3));
    }
}

以上代码结果：
come in add method
12
32
6