java - 子类 toString 打印 null？ (对不同的toStrings使用相同的参数)

Question

我正在尝试制作一个疯狂的库游戏，用户将输入 5 个变量(名词、形容词、动词、副词、第二个名词)，然后这些变量将在我的子类中用于不同的“库”。问题是，当我输入参数时，它会将它们打印为空。我确信有一种简单的方法可以对不同的 toString 使用相同的输入，但我对继承很陌生，并且不确定这部分是如何工作的。

(我查看了其他 toString null 问题，但没有一个完全适合我的情况，或者它们的构造函数有问题。我相当确定我的问题没有问题。)

这是我的短语父类(super class):

public class Phrase 
{
    private String noun;
    private String adjective;
    private String verb;
    private String adverb;
    private String noun2;

    public Phrase (String n, String a, String v, String ad, String n2)
    {
        n=noun;
        a=adjective;
        v=verb;
        ad=adverb;
        n2=noun2;
    }

    public String getNoun()
    {return noun;}

    public String getAdj ()
    {return adjective;}

    public String getVerb ()
    {return verb;}

    public String getAdverb ()
    {return adverb;}

    public String get2Noun ()
    {return noun2;}

    //i'll need the get methods in the libs classes and the set methods in the 
    while loop, if user wants to change parameters

    public void setNoun (String Newnoun)
    {noun=Newnoun;}

    public void setAdj (String newAdj)
    {adjective=newAdj;}

    public void setVerb (String newVrb)
    {verb=newVrb;}

    public void setAdverb (String newAdv)
    {adverb=newAdv;}

    public void set2Noun (String newNoun2)
    {noun2=newNoun2;}

}

这是我的子类:

public class Obama extends Phrase
{
    public Obama(String noun, String adjective, String verb, String adverb, 
            String noun2)
    {super (noun, adjective, verb, adverb, noun2);}

    public String getNoun()
    {return super.getNoun();}

    public String getAdj ()
    {return super.getAdj();}

    public String getVerb ()
    {return super.getVerb();}

    public String getAdverb ()
    {return super.getAdverb();}

    public String get2Noun (String n)
    {return super.get2Noun();}


    public String toString()
    {
        return ("there is a " + super.getAdj() + " " + super.getNoun() +" on the 
                floor! It is " + super.getVerb() +"ing " + super.getAdverb() +". Next to it 
                is a " + super.get2Noun()); 
    }


}

这是我的司机:

public class Madlibsdriver 
{
    static Scanner scan= new Scanner (System.in);
    public static void main(String[] args) 
    {

        System.out.print ("Welcome to Mad libs!");
        System.out.println();
        System.out.println("-------------------------------------------- ");
        System.out.println("Enter a noun:");
        String ip1= scan.nextLine();
        System.out.println("Enter an adjective:");
        String ip2= scan.nextLine();
        System.out.println ("Enter a verb:");
        String ip3= scan.nextLine();
        System.out.println ("Enter an adverb (ex: angrily) :");
        String ip4= scan.nextLine();
        System.out.println ("Enter another noun:");
        String ip5= scan.nextLine();

        Phrase obama= new Obama(ip1, ip2, ip3, ip4, ip5);

        System.out.println();
        System.out.print (obama.toString());

    }

}

Answer 1

您已经交换了构造函数中的参数，设置了传入的值(而不是使用它们来设置本地字段)。使用 this 关键字捕获此类错误，例如

public Phrase (String n, String a, String v, String ad, String n2)
{
    this.noun = n;
    this.adjective = a;
    this.verb = v;
    this.adverb = ad;
    this.noun2 = n2;
}