// 单条表达式语句
(args)->expression

// 多条表达式语句
(args)->{
  expression;
  expression;
}

import java.util.function.BiFunction;
import java.util.function.Function;

import org.junit.Test;

public class LambdaTest {

    // 没有参数没有返回值的lambda
    @Test
    public void testRunnable() {
        Runnable runnable = () -> System.out.println("this is a Runnable1!");
        new Thread(runnable).start();
        runnable = () -> {
            System.out.println("this is a Runnable2!");
        };
        new Thread(runnable).start();

        runnable = () -> {
            String x = "this is a Runnable3!";
            System.out.println(x);
        };
        new Thread(runnable).start();

        runnable = this::printlnNow;
        new Thread(runnable).start();

        new Thread(() -> System.out.println("this is a Runnable1!")).start();

        new Thread(() -> {
            System.out.println("this is a Runnable2!");
        }).start();

        new Thread(() -> {
            System.out.println("this is a Runnable2!");
        }).start();

        new Thread(() -> {
            String x = "this is a Runnable3!";
            System.out.println(x);
        }).start();

        new Thread(this::printlnNow).start();
    }
    // 一个参数有返回值的lambda
    @Test
    public void testFunction() {
        Function<String, Integer> function = (input) -> Integer.valueOf(input);
        System.out.println(function.apply("1234"));
        function = input -> Integer.valueOf(input);
        System.out.println(function.apply("1234"));
        function = Integer::valueOf;
        System.out.println(function.apply("1234"));
        function = input -> {
            input = input + "";
            return Integer.valueOf(input);
        };
        System.out.println(function.apply("1234"));
    }

    // 多个参数有返回值的lambda
    @Test
    public void testBiFunction() {
        BiFunction<Integer, Integer, Integer> biFunction = (a, b) -> Math.min(a, b);
        // biFunction = a, b -> Math.min(a, b); // error
        System.out.println("min value is : " + biFunction.apply(1, 2));
        biFunction = Math::max;
        System.out.println("max value is : " + biFunction.apply(1, 2));
    }

    public void printlnNow() {
        System.out.println("now is " + System.currentTimeMillis());
    }
}