Java8之函數式接口及常用函數式接口講解

@FunctionalInterface
public interface Runnable {
    /**
     * When an object implementing interface <code>Runnable</code> is used
     * to create a thread, starting the thread causes the object's
     * <code>run</code> method to be called in that separately executing
     * thread.
     * <p>
     * The general contract of the method <code>run</code> is that it may
     * take any action whatsoever.
     *
     * @see     java.lang.Thread#run()
     */
    public abstract void run();
}

@FunctionalInterface
public interface SingleAbstraMethodInterface {
    public abstract void singleMethod();
}

public class Test {
    public void testMethod(SingleAbstraMethodInterface single){
        System.out.println("即將執行函數式接口外部定義方法");
        single.singleMethod();
    }
    public static void main(String[] args) {
        Test test = new Test();
        test.testMethod(new SingleAbstraMethodInterface() {
            @Override
            public void singleMethod() {
                System.out.println("執行函數式接口定義方法");
            }
        });
    }
}

public static void main(String[] args) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("run方法執行瞭");
            }
        }).start();
}

@FunctionalInterface
public interface Runnable {
    public abstract void run();
}

public static void main(String[] args) {
        new Thread(()-> {
           System.out.println("run方法執行瞭");
        }).start();
}

@FunctionalInterface
public interface Supplier<T> {
    /**
     * Gets a result.
     * @return a result
     */
    T get();
}

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Girl {

    private String name;

    private Double size;

    private Double price;

    public static Girl create(final Supplier<Girl> supplier) {
        return supplier.get();
    }

    public static void main(String[] args) {
    	//創建對象
        Girl girl1 = Girl.create(Girl::new);
        Girl girl2 = Girl.create(()-> new Girl("lily",33d,1700d));
        Girl girl = null;
        //orElseGet
        Girl girl3 = Optional.ofNullable(girl).orElseGet(Girl::new);
    }
    
}

@FunctionalInterface
public interface Consumer<T> {

    /**
     * Performs this operation on the given argument.
     *
     * @param t the input argument
     */
    void accept(T t);

    /**
     * Returns a composed {@code Consumer} that performs, in sequence, this
     * operation followed by the {@code after} operation. If performing either
     * operation throws an exception, it is relayed to the caller of the
     * composed operation.  If performing this operation throws an exception,
     * the {@code after} operation will not be performed.
     *
     * @param after the operation to perform after this operation
     * @return a composed {@code Consumer} that performs in sequence this
     * operation followed by the {@code after} operation
     * @throws NullPointerException if {@code after} is null
     */
    default Consumer<T> andThen(Consumer<? super T> after) {
        Objects.requireNonNull(after);
        return (T t) -> { accept(t); after.accept(t); };
    }
}

	Supplier<Girl> supplier = ()-> new Girl("lucy",33d,1700d);
	Consumer<Girl> consumer = (Girl g)->{
	   System.out.println(g.toString());
	};
	consumer.accept(supplier.get());
	ArrayList<Integer> list = Lists.newArrayList(1, 2, 3, 4, 5);
    list.forEach(System.out::println);

@FunctionalInterface
public interface Predicate<T> {

    /**
     * Evaluates this predicate on the given argument.
     *
     * @param t the input argument
     * @return {@code true} if the input argument matches the predicate,
     * otherwise {@code false}
     */
    boolean test(T t);
}

		Supplier<Girl> supplier = ()-> new Girl("lucy",33d,1700d);
        Predicate<Girl> girl36d = (Girl g)-> Objects.equals(g.getSize(),36d);
        Predicate<Girl> girl33d = (Girl g)-> Objects.equals(g.getSize(),33d);
        boolean test33 = girl33d.test(supplier.get());
        boolean test36 = girl36d.test(supplier.get());
        System.out.println(supplier.get().getName() +"是否為[36d] ："+test36);
        System.out.println(supplier.get().getName() +"是否為[33d] ："+test33);

		ArrayList<Girl> list = Lists.newArrayList();
        list.add(new Girl("露西", 33d, 2000d));
        list.add(new Girl("格蕾絲", 36d, 3000d));
        list.add(new Girl("安娜", 28d, 1500d));
        list.add(new Girl("克瑞斯", 31d, 1800d));
        Predicate<Girl> greaterThan30d = (Girl g)-> g.getSize()>=30d;
        list.stream().filter(greaterThan30d).forEach(System.out::println);

@FunctionalInterface
public interface Function<T, R> {
    /**
     * Applies this function to the given argument.
     *
     * @param t the function argument
     * @return the function result
     */
    R apply(T t);
}

Supplier<Girl> supplier = ()-> new Girl("lucy",33d,1700d);
 Function<Girl,String> girlMark = (Girl g)-> g.getName()+"的尺寸是"+g.getSize()+"，每次能賺"+g.getPrice()+"。";
 System.out.println(girlMark.apply(supplier.get()));