看看下面的继承关系就知道了。
public class ArrayList extends AbstractList
implements List, RandomAccess, Cloneable, java.io.Serializable;public abstract class AbstractList extends AbstractCollection implements Listpublic abstract class AbstractCollection implements Collection public interface List extends Collection 明白了吗?用到了java的多态性。
public class ArrayList extends AbstractList
implements List, RandomAccess, Cloneable, java.io.Serializable;public abstract class AbstractList extends AbstractCollection implements Listpublic abstract class AbstractCollection implements Collection public interface List extends Collection 明白了吗?用到了java的多态性。
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