java - 使用多态性打印字符串出现次数

Question

我无法弄清楚如何打印出“Dr”标题出现在测试程序的数组对象中的次数，因为它们包含多个字符串。使用 equals 类是解决这个问题的最佳方法吗？

注意:我正在使用继承和多态性。

public class Driver {

public static void main(String[ ] args) {
    Person[] persons = new Person[5];

    persons[0] = new Person("John Smith");
    persons[1] = new Person();
    persons[2] = new TitledPerson("Rowan Bean", "Mr");
    persons[3] = new TitledPerson("Phil McGraw", "Dr");
    persons[4] = new TitledPerson("Hugo Strange", "Dr");

    System.out.println("Person 3 and 4 are equal: " + persons[2].equals(persons[3]));
    System.out.println();

    String search = "Dr";
    int counter = 0;
    for(int i = 0; i < persons.length; i++) {
        System.out.println(persons[i]); 

        if(persons[i] instanceof TitledPerson) {
            if(persons[i].equals(search)) {
            counter++;
            }
        }
    }
    System.out.println();

System.out.println("There are " + counter + " 'Dr' titles listed.");
}   
}

人员类别:

public class Person {

private String name;
private final static String DEFAULT_NAME = "N/A";

public Person() {
    this(DEFAULT_NAME);
}

public Person(String name) {
    this.name = name;
}

public void setName(String name) {
    this.name = name;
}

public String getName() {
    return name;
}

public String toString() {
    return "Name: " + name;
}

public boolean equals(Object obj) {
    if(obj instanceof Person) {
        Person otherPerson = (Person) obj;
        return name.equalsIgnoreCase(otherPerson.getName());
    } else {
        return false;
    }
}

}

TitledPerson 类:

public class TitledPerson extends Person { 

private String title;

public TitledPerson() {
}

public TitledPerson(String name, String title) {
    super(name);
    this.title = title;
}

public String getTitle() {
    return title;
}

public void setTitle(String title) {
    this.title = title;
}

@Override
public String toString() {
    String parentString = super.toString();
    parentString += ", " + title;
    return parentString;
}

@Override
public boolean equals(Object obj) {
    if(obj instanceof TitledPerson) {
        TitledPerson otherPers = (TitledPerson) obj;
        return super.equals(obj) && this.title.equalsIgnoreCase(otherPers.title);                               
    } else {
        return false;
    }
}

}

Answer 1

更改为使用 TitledPerson 类中的 getTitle，同时与 search 关键字进行比较。

if(((TitledPerson)persons[i]).getTitle().equals(search)) {
        counter++;      
}