如何创建子类？ [关闭]

Question

我是编码的初学者，我一直在寻找整个互联网，并没有真正出来，并给我一个关于如何使用扩展方法以及如何正确使用 super( ) 方法。我有点坚持这一点，想知道是否有人可以展示或给我一个很好的例子。我的项目是定义一个类 Diploma 及其子类 DiplomaWithHonors，以便一些陈述显示他们的学术成就。谢谢你的帮助！好吧，既然我对这个问题进行了“刺伤”，那么如果有人可以帮助解决这个问题，我的 return 语句就会出错......

     public class Diploma
      {
       public String fullName;
       public String course;
       int output = Diploma();

        public Diploma(String name, String info)
         {
         fullName = name;
         course = info;
         }
        public String toString()
         {
          return "This certifies that \n" + fullName + " \n has completed a course in " + course;
           }
        }

         public class DiplomaWithHonors extends Diploma
      {
        public DiplomaWithHonors( String name, String info ) 
      {
        super( name, info );
      }
       public String toString() 
      {
      return "This certifies that \n" + fullName + " \n has completed a course in " +   course+ "\n*** with honors ***";
      }
        }
      public String toString()
       {
        Diploma[] diplomas = new Diploma[2];
        diplomas[ 0 ] = new Diploma("Murray Smith", "Gardening");
        diplomas[ 1 ] = new DiplomaWithHonors("Lisa Smith", "Evolutionary Psychology");

        for( int i = 0; i< diplomas.length; i++) 
        {
         System.out.println( diplomas[ i ] );
        }
       }
        return output;
       }

P.S 很抱歉样式故障，我有点搞砸了复制粘贴。

Answer 1

super 不是方法； it's a keyword. 在某些情况下，它可能被称为或使用作为方法，但它实际上是一个关键字。上面的链接将为您提供大量有用的信息，以及一些关于继承的花絮。

除此之外，这听起来像是两个实体之间的直接关系：

• Diploma 应该是您正在使用的基本实体；它包含诸如收件人姓名、他们的 GPA 以及他们正在接受的学位科目等信息。

• DiplomaWithHonors 听起来对于不同的 GPA 来说是一种不同的荣誉。

非常原始结构可能看起来像这样。假设定义了字段。

public class Diploma {
    public Diploma(String name, double GPA, String degreeField, DiplomaType diplomaType) {
        this.name = name;
        this.GPA = GPA;
        this.degreeField = degreeField;
        this.diplomaType = diplomaType;
    }
}

public class DiplomaWithHonors extends Diploma {
    public DiplomaWithHonors(String name, double GPA, String degreeField, DiplomaType diplomaType) {
        super(name, GPA, degreeField, diplomaType);
        calculateHonors();
     }
}

请注意，构造函数上下文中的super 必须是该构造函数内部引用的第一个事物。

Answer 2

查看此示例的 toString() 方法

import java.util.List;


public class Diploma {
    private String student;

    public String getStudent() {
        return student;
    }

    public void setStudent(String student) {
        this.student = student;
    }

    @Override
    public String toString() {
        return "Diploma [student=" + student + "]";
    }

    public static void main(String[] args){
        DiplomaWithHonors d1 = new DiplomaWithHonors();
        d1.setStudent("John");
        String[] achievements = {"Golden Medal","Silver Medal"};
        d1.setAchievements(achievements);

        System.out.println(d1);

        DiplomaWithoutAnyHonors d2 = new DiplomaWithoutAnyHonors();
        d2.setStudent("Doe");
        String[] homeworksDoneByStackOverflow = {"How to use super"};
        d2.setHomeworksDoneByStackOverflow(homeworksDoneByStackOverflow );

        System.out.println(d2);
    }
}

和

import java.util.Arrays;



public class DiplomaWithHonors extends Diploma {
    private String[] achievements;

    public String[] getAchievements() {
        return achievements;
    }

    public void setAchievements(String[] achievements) {
        this.achievements = achievements;
    }

    @Override
    public String toString() {
        return "DiplomaWithHonors [achievements=" + Arrays.asList(achievements)
                + ", toString()=" + super.toString() + "]";
    }


}

和

import java.util.Arrays;



public class DiplomaWithoutAnyHonors extends Diploma{
    private String[] homeworksDoneByStackOverflow;

    public String[] getHomeworksDoneByStackOverflow() {
        return homeworksDoneByStackOverflow;
    }

    public void setHomeworksDoneByStackOverflow(
            String[] homeworksDoneByStackOverflow) {
        this.homeworksDoneByStackOverflow = homeworksDoneByStackOverflow;
    }

    @Override
    public String toString() {
        return "DiplomaWithoutAnyHonors [homeworksDoneByStackOverflow="
                + Arrays.asList(homeworksDoneByStackOverflow) + ", toString()="
                + super.toString() + "]";
    }


}