public int add(int x, int y) {
  return x + y;
 }

 (int x, int y) -> x + y;

 (x, y) -> x + y; //返回两数之和

 (x, y) -> { return x + y; } //显式指明返回值

 () -> { System.out.println("Hello Lambda!"); }

 c -> { return c.size(); }

 @FunctionalInterface
 public interface Runnable { void run(); }
 public interface Callable<V> { V call() throws Exception; }
 public interface ActionListener { void actionPerformed(ActionEvent e); }
 public interface Comparator<T> { int compare(T o1, T o2); boolean equals(Object obj); }

 Runnable r1 = () -> {System.out.println("Hello Lambda!");}; 

 Object obj = r1; 

 Object obj = () -> {System.out.println("Hello Lambda!");}; // ERROR! Object is not a functional interface!

 Object o = (Runnable) () -> { System.out.println("hi"); }; // correct 

System.out.println( () -> {} ); //错误! 目标类型不明 

 System.out.println( (Runnable)() -> {} ); // 正确

@FunctionalInterface
 public interface MyRunnable {
  public void run();
 }

Runnable r1 = () -> {System.out.println("Hello Lambda!");};
 MyRunnable2 r2 = () -> {System.out.println("Hello Lambda!");};

 @FunctionalInterface
 public interface Function<T, R> { 
  R apply(T t);
 }

 @FunctionalInterface
 public interface Consumer<T> {
  void accept(T t);
 }

@FunctionalInterface
 public interface Predicate<T> {
  boolean test(T t);
 }

 Thread oldSchool = new Thread( new Runnable () {
  @Override
  public void run() {
   System.out.println("This is from an anonymous class.");
  }
 } );
 Thread gaoDuanDaQiShangDangCi = new Thread( () -> {
  System.out.println("This is from an anonymous method (lambda exp).");
 } );

 for(Object o: list) { // 外部迭代
  System.out.println(o);
 }

list.forEach(o -> {System.out.println(o);}); //forEach函数实现内部迭代

 List<Shape> shapes = ...
 shapes.stream()
  .filter(s -> s.getColor() == BLUE)
  .forEach(s -> s.setColor(RED));

 shapes.parallelStream(); // 或shapes.stream().parallel()

//给出一个String类型的数组，找出其中所有不重复的素数
 public void distinctPrimary(String... numbers) {
  List<String> l = Arrays.asList(numbers);
  List<Integer> r = l.stream()
    .map(e -> new Integer(e))
    .filter(e -> Primes.isPrime(e))
    .distinct()
    .collect(Collectors.toList());
  System.out.println("distinctPrimary result is: " + r);
 }

 //给出一个String类型的数组，找出其中各个素数，并统计其出现次数
 public void primaryOccurrence(String... numbers) {
  List<String> l = Arrays.asList(numbers);
  Map<Integer, Integer> r = l.stream()
   .map(e -> new Integer(e))
   .filter(e -> Primes.isPrime(e))
   .collect( Collectors.groupingBy(p->p, Collectors.summingInt(p->1)) );
  System.out.println("primaryOccurrence result is: " + r);
 }

 Collectors.groupingBy(p->p, Collectors.summingInt(p->1))

 //给出一个String类型的数组，求其中所有不重复素数的和
 public void distinctPrimarySum(String... numbers) {
  List<String> l = Arrays.asList(numbers);
  int sum = l.stream()
   .map(e -> new Integer(e))
   .filter(e -> Primes.isPrime(e))
   .distinct()
   .reduce(0, (x,y) -> x+y); // equivalent to .sum()
  System.out.println("distinctPrimarySum result is: " + sum);
 }

 // 统计年龄在25-35岁的男女人数、比例
 public void boysAndGirls(List<Person> persons) {
  Map<Integer, Integer> result = persons.parallelStream().filter(p -> p.getAge()>=25 && p.getAge()<=35).
   collect(
    Collectors.groupingBy(p->p.getSex(), Collectors.summingInt(p->1))
  );
  System.out.print("boysAndGirls result is " + result);
  System.out.println(", ratio (male : female) is " + (float)result.get(Person.MALE)/result.get(Person.FEMALE));
 }

 // 嵌套的λ表达式
 Callable<Runnable> c1 = () -> () -> { System.out.println("Nested lambda"); };
 c1.call().run();
 // 用在条件表达式中
 Callable<Integer> c2 = true ? (() -> 42) : (() -> 24);
 System.out.println(c2.call());
 // 定义一个递归函数，注意须用this限定
 protected UnaryOperator<Integer> factorial = i -> i == 0 ? 1 : i * this.factorial.apply( i - 1 );
 ...
 System.out.println(factorial.apply(3));

 int five = ( (x, y) -> x + y ) (2, 3); // ERROR! try to call a lambda in-place

 ... 
 int tmp1 = 1; //包围类的成员变量
 static int tmp2 = 2; //包围类的静态成员变量
 public void testCapture() {
  int tmp3 = 3; //没有声明为final，但是effectively final的本地变量
  final int tmp4 = 4; //声明为final的本地变量
  int tmp5 = 5; //普通本地变量
  Function<Integer, Integer> f1 = i -> i + tmp1;
  Function<Integer, Integer> f2 = i -> i + tmp2;
  Function<Integer, Integer> f3 = i -> i + tmp3;
  Function<Integer, Integer> f4 = i -> i + tmp4;
  Function<Integer, Integer> f5 = i -> {
   tmp5 += i; // 编译错！对tmp5赋值导致它不是effectively final的
   return tmp5;
  };
  ...
  tmp5 = 9; // 编译错！对tmp5赋值导致它不是effectively final的
 }
 ...

 Integer::parseInt //静态方法引用
 System.out::print //实例方法引用
 Person::new  //构造器引用

//c1 与 c2 是一样的（静态方法引用）
 Comparator<Integer> c2 = (x, y) -> Integer.compare(x, y);
 Comparator<Integer> c1 = Integer::compare;
 //下面两句是一样的（实例方法引用1）
 persons.forEach(e -> System.out.println(e));
 persons.forEach(System.out::println);
 //下面两句是一样的（实例方法引用2）
 persons.forEach(person -> person.eat());
 persons.forEach(Person::eat);
 //下面两句是一样的（构造器引用）
 strList.stream().map(s -> new Integer(s));
 strList.stream().map(Integer::new);

public void distinctPrimarySum(String... numbers) {
  List<String> l = Arrays.asList(numbers);
  int sum = l.stream().map(Integer::new).filter(Primes::isPrime).distinct().sum();
  System.out.println("distinctPrimarySum result is: " + sum);
 } 

 super::toString //引用某个对象的父类方法
 String[]::new //引用一个数组的构造器

 public interface MyInterf {
   String m1();
  default String m2() {
   return "Hello default method!";
  }
 } 

public class Sub implements Base1, Base2 {
  public void hello() {
   Base1.super.hello(); //使用Base1的实现
  }
 }

 public interface MyInterf {
  String m1();
  default String m2() {
   return "Hello default method!";
  }
  static String m3() {
   return "Hello static method in Interface!";
  }
 }

 Stream.generate(Math::random).limit(5).forEach(System.out::println);