interface Playable {void

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interface Playable {void play();}interface Bounceable {void play();}interface Rollable extends Playa

参考答案:

正确答案:

\r\n

错。\"interface Rollable extends Playable, Bounceable\"没有问题。interface 可继承多个
interfaces,所以这里没错。问题出在interface Rollable 里的\"Ball ball = new Ball(\"PingPang\");\"。
任何在interface 里声明的interface variable (接口变量,也可称成员变