Java8接口中引入default关键字的本质原因详析

public interface IDemo {
    void func1();
}

public class CDemo1 implements IDemo{
    @Override
    public void func1() {
    }
}

public class CDemo2 implements IDemo{
    @Override
    public void func1() {
    }
}

public interface IDemo {
    void func1();
    void func2();
}

default Stream<E> stream() {
 return StreamSupport.stream(spliterator(), false);
}

default Stream<E> parallelStream() {
    return StreamSupport.stream(spliterator(), true);
}

default Spliterator<E> spliterator() {
    return Spliterators.spliterator(this, 0);
}

default boolean removeIf(Predicate<? super E> filter) {
    Objects.requireNonNull(filter);
    boolean removed = false;
    final Iterator<E> each = iterator();
    while (each.hasNext()) {
        if (filter.test(each.next())) {
            each.remove();
            removed = true;
        }
    }
    return removed;
}

public interface IDemo {
    void func1();
    void func2();
    default void func3(){
        System.out.println("this is default func2");
    }
}

public static void main(String[] args) {
    CDemo1 cd1=new CDemo1();
    cd1.func3();
}

static  void func4(){
    System.out.println("this is static func4");
}

IDemo.func4();