Question

我已经创建了一个Person类，以及一个继承自它的类，即教授类。现在，我已经在Person课程和教授课程中声明了我的二传手。我希望构造函数通过调用setter并执行验证来设置变量。我做的正确吗？如果没有，我该怎么做才能纠正它？

人类：

public class Person {


private String firstName;
private String lastName;

public Person(String firstname,String lastname) throws InvalidDataException
{
    setFirstName(firstname);
    setLastName(lastname);
}

public String getFirstName() {
    return firstName;
}

private void setFirstName(String firstName) throws InvalidDataException {

 if ( firstName == null || firstName.length() < 1) {
      throw new InvalidDataException("Person Must have First Name");}

    this.firstName = firstName;
}

public String getLastName() {
    return lastName;
}

private void setLastName(String lastName) throws InvalidDataException {

     if ( lastName == null ||  lastName.length() < 1) {
          throw new InvalidDataException("Person Must have Last Name");}

    this.lastName = lastName;
}

教授班

public class Professor extends Person {


private String  professorID;

public Professor(String professorID,String firstname, String lastname) throws InvalidDataException {
    super(firstname, lastname);
    // TODO Auto-generated constructor stub
    this.setID(professorID);

}

private void setID(String professorID) throws InvalidDataException{

     if ( professorID == null ||professorID.length() < 1) {
          throw new InvalidDataException("Person Must have ID");}
    this.professorID = professorID;
}

public String getID()
{
    return this.professorID;
}


public void printData()
{
     System.out.println("Professor ID: " + this.getID() + " First Name: " + this.getFirstName() + " Last Name: " + this.getLastName());
}

}

Answer 1

考虑到你的“ setters ”主要检查字符串既不是空也不是空，你可能有一个静态或实用方法就是这样做，并在构造函数（和/或公共setter）中调用它）在分配给班级成员之前。

public class Person {

    protected void check( String s, String msg ){
        if( s == null ||s.length < 1) {
            throw new InvalidDataException(msg);
        }
    }

    public Person(String firstname,String lastname) throws InvalidDataException{
        check( firstname, "Person's first name missing" );
        check( lastname, "Person's last name missing" );
        this.firstname = firstname;
        this.lastname = lastname;
    }

    public void setFirstname( String firstname ){
        check( firstname, "Person's first name missing" );
        this.firstname = firstname;
    }
}

但是豆子不应该需要这样的守卫。如果有GUI，GUI应该进行验证，只将正确的值传递给对象构造。

Answer 2

将setter声明为private是一种不好的做法。因为setter的目标是从类实例中调用它们在该类之外。如果你真的想用构造函数填充你的类属性，你可以创建一个私有函数来构建你的类。 ** ps：如果你的类属性很容易填充，你可以在构造函数中填充它们。你不需要任何支持函数。

Answer 3

最好的方法是将Person类成员设置为protected而不是private。无论如何，定居者和吸气者应该在OOD公开。

私有Setter的Java继承

3 个答案: