父类可以不同于子类吗？

Question

Lets say we have:

1) Superclass containing a string parameter: companyName 2) Subclasses containing string parameters: firstName, lastName

If we have subClassA, subClassB, subClassC, subClassD, etc. Can these subclasses have same superclass, but with different strings companyName, or the companyName meaning/value will be the same for every subclass no matter what?

Answer 1

Every instance of the parent class can have a different value for companyName whether it's of a subtype or not.

public class Parent {
  private final String companyName;

  public Parent(String name) {
    this.companyName = name;      // ignoring error-checking here
  }

  public String getCompanyName() {
    return companyName;
  }
}

public class Subsidiary extends Parent {
  private final String subsidiaryName;

  public Subsidiary(String parentName, String subsidiaryName) {
    super(parentName);
    this.subsidiaryName = subsidiaryName;
  }

  public String getSubsidiaryName() {
    return subsidiaryName;
  }
}

In some client code you can call:

Subsidiary subsidiary = new Subsidiary("Holdings, Inc.", "Puppet");
System.out.println(subsidiary.getCompanyName() + " owns "
    + subsidiary.getSubsidiaryName());

You see, the child-type object inherits the accessor method getCompanyName that gives it access to the information in the parent section of the object.