一、四大内置核心函数式接口

  Consumer<T>消费型接口：

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

//测试示例
@Test
void test(){
    comsumerFunctionalTest("hello world!",e-> System.out.println(e));
}

void comsumerFunctionalTest(String msg,Consumer<String> consumer){
    consumer.accept(msg);
}

  Supplier<T>供给型接口：

//源码
@FunctionalInterface
public interface Supplier<T> {
    T get();
}

//测试示例
@Test
void test(){
    supplierFunctionalTest(()-> String.valueOf(new Random().nextInt()));
}

void supplierFunctionalTest(Supplier<String> supplier){
    String result = supplier.get();
    System.out.println(result);
}

  Function<T, R>函数型接口：

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

//测试示例
@Test
void test(){
    functionFunctionalTest(1024,(e)-> "num"+String.valueOf(e));
}

void functionFunctionalTest(Integer num,Function<Integer,String> function){
    String result = function.apply(num);
    System.out.println(result);
}

  Predicate<T>断言型接口：

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

//测试示例
 @Test
void test(){
    predicateFunctionalTest("hello world!",(e)-> e.length()>5);
}

void predicateFunctionalTest(String name, Predicate<String> predicate){
    boolean result = predicate.test(name);
    System.out.println(result);
}

二、常用函数式接口

2.1 Runnable接口

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

//测试示例
@Test
void test(){
    new Thread(()->{
        System.out.println("hello world!");
    },"thread-1").start();
}

2.2 Comparator<T>接口

//源码
@FunctionalInterface
public interface Comparator<T> {
    int compare(T o1, T o2);
｝

//测试示例
@Test
void test(){
    Student stu1 = new Student(23);
    Student stu2 = new Student(24);
    comparatorFunctionalTest(stu1,stu2,(e1,e2)-> Integer.compare(e1.getAge(),e2.getAge()));
}

void comparatorFunctionalTest(Student stu1, Student stu2, Comparator<Student> comparator){
    int result =  comparator.compare(stu1,stu2);
    System.out.println(result);
}

2.3 GenericFutureListener接口

//源码
public interface GenericFutureListener<F extends Future<?>> extends EventListener {
    void operationComplete(F var1) throws Exception;
}

//测试示例
private static final int MAX_RETRY = 5;
private static void connect(final String host,final int port,final int retry,final Bootstrap bootstrap){
    bootstrap.connect(host,port).addListener(future ->  {
    if (future.isSuccess()){
        System.out.println("客户端连接成功！");
    }else if(retry == 0){
        System.out.println("连接失败！");
    }
    else {
       int order = (MAX_RETRY - retry) + 1;
       int delay = 1 << order;
       bootstrap.config().group().schedule(() -> connect(host, port, retry - 1, bootstrap), delay, TimeUnit.SECONDS);
   }});
}