SE450: Types: Abstraction [32/47] Previous pageContentsNext page

We can look at an object at progressively more abstract types.

Consider java.util.LinkedList:

file:types/abstractTypes/Main.java [source] [doc-public] [doc-private]
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package types.abstractTypes;
public class Main {
  private Main() {}
  public static void main(String[] args) {
    java.util.LinkedList<?> o1 = new java.util.LinkedList<>();
    java.util.AbstractSequentialList<?> o2 = o1;
    java.util.AbstractList<?> o3 = o1;
    java.util.AbstractCollection<?> o4 = o1;
    java.lang.Object o5 = o1;

    java.util.List<?> i1 = o1;
    java.util.Collection<?> i2 = o1;

    java.io.Serializable i3 = o1;
    java.lang.Cloneable i4 = o1;
  }
}

There are nine references to a single object.

Each reference has a different set of capabilities.

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