接口作为成员变量类型以及参数或返回值

接口作为成员变量类型

public class Hero {
    private String name;
    private Skill skill;

    public void attack(){
        System.out.println("我叫"+name+"开始");
        skill.use();
        System.out.println("完成");
    }
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Skill getSkill() {
        return skill;
    }

    public void setSkill(Skill skill) {
        this.skill = skill;
    }

    public Hero() {
    }

    public Hero(String name, Skill skill) {
        this.name = name;
        this.skill = skill;
    }
}

public interface Skill {
    void use();
}

public class SkillImpl implements Skill{
    @Override
    public void use() {
        System.out.println("放技能");
    }
}

public class DemoMain {
    public static void main(String[] args) {
        Hero hero = new Hero();
        hero.setName("张三");
//        hero.setSkill(new SkillImpl());
        //还可以使用匿名内部类
//        Skill skill =  new Skill() {
//            @Override
//            public void use() {
//                System.out.println("释放技能");
//            }
//        };
//        hero.setSkill(skill);
        //同时使用匿名内部类和匿名对象
        hero.setSkill(new Skill() {
            @Override
            public void use() {
                System.out.println("释放技能");
            }
        });
        hero.attack();
    }
}

 

运行结果：

 

 

 

 

 

 

接口作为方法的参数或返回值 

public class DemoInterface {
    public static void main(String[] args) {
        //左边是接口名称，右边是实现类名称，这就是多态的写法
        List<String> list = new ArrayList<>();
        List<String> list1 = addNames(list);
        for (int i = 0; i < list1.size(); i++) {
            System.out.println(list1.get(i));
        }
    }

    public static List<String> addNames(List<String> list){
        list.add("张三");
        list.add("李四");
        list.add("王五");
        return list;
    }
}

运行结果：