java 通用構造函數未定義

Question

我正在學習 java 和 generics 並遇到了一些問題。 我已閱讀 Stackoverflow 上發布的有關泛型的所有問題，但不明白為什么會發生此錯誤

class Student{

    String name;
    float marks;

    Student(String name,float marks){
        this.name = name;
        this.marks = marks;
    }

}

public class GenericClassEx<T> {
    
    T obj;
        GenericClassEx(T data){
       
        this.obj = data;
    }

    public T getObject(){
        return this.obj;
    }

    public static void main(String[] args) {
        Float d = new Float(10);
        GenericClassEx<Student> iobj= new GenericClassEx <Student> ("prince",d);
        System.out.println(iobj.getObject());
    }

}

當我運行這段代碼時，它說

GenericClassEx.java:28: error: constructor GenericClassEx in class GenericClassEx<T> cannot be applied to given types;
        GenericClassEx<Student> iobj= new GenericClassEx <Student> ("prince",d);
                                      ^
  required: Student
  found: String,Float
  reason: actual and formal argument lists differ in length
  where T is a type-variable:
    T extends Object declared in class GenericClassEx
Note: GenericClassEx.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
1 error

Answer 1

您需要將Student的 object 傳遞給構造函數GenericClassEx(T data) 。 取而代之的是，您將兩個 arguments、 "prince"和d傳遞給它。

代替

GenericClassEx<Student> iobj= new GenericClassEx <Student> ("prince",d);

和

GenericClassEx<Student> iobj = new GenericClassEx<Student>(new Student("prince", d));

附帶說明一下，構造函數Float(double value)自 Java-9 以來已被棄用。

代替

Float d = new Float(10);

和

Float d = Float.valueOf(10);