接口定义

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

函数式接口

  • JSR 335
A functional interface is an interface that has just one abstract method, and thus
represents a single function contract. (In some cases, this "single" method may take
the form of multiple abstract methods with override-equivalent signatures inherited
from superinterfaces; in this case, the inherited methods logically represent a single
method.)

  • 单抽象方法接口Single Abstract Method Interfaces(SAM Interfaces): 表达逻辑上的单一功能约定

  • java.lang.Runnable是函数式接口，只有一个抽象方法

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