Runnable runnable = new Runnable() {
    @Override
    public void run() {
        System.out.println("run");
    }
};

Runnable runnable = ()->System.out.println("run");

/*Runnable runnable = new Runnable() {@Overridepublic void run() {System.out.println("run");}};*/

Runnable runnable = ()->System.out.println("run");

/*BinaryOperator<Long> add = new BinaryOperator<Long>() {@Override
public Long apply(Long x, Long y) {return x + y;}};*/

BinaryOperator<Long> add = (x, y) -> x + y;

/*ActionListener listener = new ActionListener() {@Overridepublic void actionPerformed(ActionEvent e) {System.out.println("button clicked");}};*/

ActionListener listener = event -> System.out.println("button clicked");

/*ActionListener actionListener = new ActionListener() {@Overridepublic void actionPerformed(ActionEvent e) {System.out.println("button clicked");System.out.println("notice other");}};*/ActionListener actionListener = event -> {System.out.println("button clicked");System.out.println("notice other");};

//正确写法

BinaryOperator<Long> add = (x, y) -> x + y;

// 错误写法

BinaryOperator<Long> add = (x, y) -> return x + y;

//正确写法

BinaryOperator<Long> add = (x, y) -> {return x + y;};

@FunctionalInterfacepublic interface Consumer<T> {

void accept(T t);

}

public interface TestComsumer<T> {void accept(T t);void apply(T x,T y);}

//示例1

Predicate<Integer> predicate = x -> x > 5;

//示例2

Predicate<String> predicate = x -> x.equals("x");

@FunctionalInterfacepublic interface Predicate<T> {

boolean test(T t);

}

//当将x进行toString后，再转成Integer就能进行大小比较，这样就不报错。

Predicate predicate = x -> Integer.parseInt(x.toString()) > 5;

//当将x进行toString后，就能跟字符”x”进行比较

Predicate predicate = x -> x.toString().equals("x");

操作类型

接口方法

惰性求值

concat() distinct() filter() flatMap() limit() map() peek()
skip() sorted() parallel() sequential() unordered()

及早求值

allMatch() anyMatch() collect() count() findAny() findFirst()
forEach() forEachOrdered() max() min() noneMatch() reduce() toArray()

//Stream中distinct方法签名

Stream<T> distinct();

//代码示例

Stream<String> stream= Stream.of("I", "love", "you", "too", "too");stream.distinct().forEach(str -> System.out.println(str));

// Stream中filter方法签名

Stream<T> filter(Predicate<? super T> predicate);

//代码示例 将oldList中大于3的元素转换成newList

List<Integer> oldList  = Arrays.asList(1,2,3,4,5);/*List<Integer> newList = new ArrayList<Integer>();for(Integer integer:oldList){if(integer>3){newList.add(integer);}}*/

List<Integer> newList = oldList.stream()

.filter(x -> x > 3).collect(toList());

// Stream中flatMap方法签名

<R> Stream<R> flatMap(Function<? super T, ? extends Stream<? extends R>> mapper);

//将多个list中的值转换成一个list

List<Integer> list1 = asList(1, 2);List<Integer> list2 = asList(3, 4);Stream<List<Integer>> listStream = Stream.of(list1, list2);List<Integer> together = listStream.flatMap(numbers -> numbers.stream()).collect(toList());

//Stream中map方法签名

<R> Stream<R> map(Function<? super T, ? extends R> mapper);

//示例代码将Integer集合转换成String集合

List<String> list = Stream.of(1, 2, 3)

.map(x -> String.valueOf(x)).collect(toList());

//Stream中sorted方法签名

Stream<T> sorted();

Stream<T> sorted(Comparator<? super T> comparator);

//代码示例

Stream<String> stream= Stream.of("I", "love", "you", "too");

//自然顺序排序

stream.sorted().forEach(str -> System.out.println(str));

//自定义排序

stream.sorted((str1, str2) -> str1.length()-str2.length()).forEach(str -> System.out.println(str));

//Stream中collect方法签名

<R, A> R collect(Collector<? super T, A, R> collector);

//toList()代码示例

List<String> list = Stream.of("a", "b" , "c")

.collect(Collectors.toList());

//toMap()代码示例

Map<String, String> map = Stream.of("a", "b", "c")

.collect(Collectors.toMap(str -> str, Function.identity()));

// Function.identity()表示返回自身，等同str -> str à源码

static <T> Function<T, T> identity() {return t -> t;}

//toSet()代码示例

Set<String> set = Stream.of("a", "b", "c").collect(Collectors.toSet());

// Stream中forEach方法签名。

void forEach(Consumer<? super T> action)

//代码示例

Stream<String> stream = Stream.of("I", "love", "you", "too");

/*stream.forEach(new Consumer<String>() {@Overridepublic void accept(String str) {System.out.println(str);}});*/

stream.forEach(str -> System.out.println(str));

//Stream中max方法签名

Optional<T> max(Comparator<? super T> comparator);

//查找字符长度最长的元素

String maxStr = Stream.of("I", "love", "you", "too")

.max(Comparator.comparing(x -> x.length())).get();

//Stream中reduce方法签名

T reduce(T identity, BinaryOperator<T> accumulator);

Optional<T> reduce(BinaryOperator<T> accumulator);

<U> U reduce(U identity,BiFunction<U, ? super T, U> accumulator,BinaryOperator<U> combiner);

//代码示例

//Optional可能为空

Optional<Integer> reduce = Stream.of(1, 2, 3).reduce((acc, element) -> acc + element);

//默认给了起始值，所以返回integerInteger reduce = Stream.of(1, 2, 3).reduce(0, (acc, element) -> acc + element);

//创建一个字符”a”的optional

Optional<String> optional = Optional.of("a");

//创建一个空的 Optional 对象，并检查其是否有值

Optional emptyOptional = Optional.empty();Optional alsoEmpty = Optional.ofNullable(null);

//使用 orElse 和 orElseGet 方法

emptyOptional.orElse("b");emptyOptional.orElseGet(() -> "c");