JavaLambda表达式详解

// JDK7匿名内部类写法
new Thread(new Runnable() {//接口名
        @Override
        public void run() {//方法名
            System.out.println("mikechen");
        }
    });

// JDK8 Lambda来创建线程
new Thread(() -> System.out.println("mikechen"));

() -> System.out.println("mikechen");

Consumer<String> con = （x） -> System.out.println(x);

Consumer<String> con = x -> System.out.println(x);

BinaryOperator<Integer> bo = (a, b) -> {
    System.out.println("函数式接口");
    return a + b;
};

(Car car) -> System.out.println("The car is: " + car.getName());

BinaryOperator<Integer> bo = (a, b) -> a + b;

BinaryOperator<Integer> bo = (Integer a, Integer b) -> {
    return a + b;
};

BinaryOperator<Integer> bo = (a, b) -> {
    return a + b;
};

(param) -> {
    System.out.println("param: " + param);
    return "return value";
}

@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface FunctionalInterface {}

public interface MyFunctionInterface<T> {
    public T getValue(T t);
}

Unexpected @FunctionalInterface annotation
@FunctionalInterface ^ WorkerInterface is not a functional interface multiple
non-overriding abstract methods found in interface WorkerInterface 1 error

//JDK 8之前
new Thread(new Runnable() {
    @Override
    public void run() {
        System.out.println("使用匿名内部类，开线程");
    }
}).start();

//JDK 8 使用lambda表达式
new Thread(() -> System.out.println("使用lambda表达式，开线程")).start();

// Java 8之前：
button.addActionListener(new ActionListener() {
    @Override
    public void actionPerfORMed(ActionEvent e) {
        System.out.println("Button被点击了使用老的方式!");
    }
});

// Java 8方式：
button.addActionListener( (e) -> {
    System.out.println("Button被点击了使用Lambda表达式!");
});

// Java 8之前：
List features = Arrays.asList("Lambdas", "Default Method", "Stream api", "Date and Time API");
for (String feature : features) {
    System.out.println(feature);
}

// Java 8之后：
List features = Arrays.asList("Lambdas", "Default Method", "Stream API", "Date and Time API");
features.forEach(n -> System.out.println(n));

// 使用Java 8的方法引用更方便，方法引用由::双冒号操作符标示，
features.forEach(System.out::println);

public static void main(String[] args) {
    List<String> list = new ArrayList<>();
    list.add("a");
    list.add("d");
    list.add("b");
    list.add("c");
    list.sort((o1,o2)->o1.compareTo(o2));
    list.forEach(System.out::println);
}

// 不使用lambda表达式为每个订单加上12%的税
List costBeforeTax = Arrays.asList(100, 200, 300, 400, 500);
for (Integer cost : costBeforeTax) {
    double price = cost + .12*cost;
    System.out.println(price);
}
// 使用lambda表达式
List costBeforeTax = Arrays.asList(100, 200, 300, 400, 500);
costBeforeTax.stream().map((cost) -> cost + .12*cost).forEach(System.out::println);

// 创建一个字符串列表，每个字符串长度大于2
List<String> filtered = strList.stream().filter(x -> x.length()> 2).collect(Collectors.toList());
System.out.printf("Original List : %s, filtered list : %s %n", strList, filtered);

// 将字符串换成大写并用逗号链接起来
List<String> G7 = Arrays.asList("USA", "Japan", "France", "Germany", "Italy", "U.K.","Canada");
String G7Countries = G7.stream().map(x -> x.toUpperCase()).collect(Collectors.joining(", "));
System.out.println(G7Countries);

//获取数字的个数、最小值、最大值、总和以及平均值
List<Integer> primes = Arrays.asList(2, 3, 5, 7, 11, 13, 17, 19, 23, 29);
IntSummaryStatistics stats = primes.stream().mapToInt((x) -> x).summaryStatistics();
System.out.println("Highest prime number in List : " + stats.getMax());
System.out.println("Lowest prime number in List : " + stats.getMin());
System.out.println("Sum of all prime numbers : " + stats.getSum());
System.out.println("Average of all prime numbers : " + stats.getAverage());