英文:
How to use compareTo method with generic T type?
问题
我有这个 UML，也许可以帮助。我在那里唯一使用的是实例变量 T[] list 和方法 f()，这个方法只是用来测试的方法。
注意：忽略 UML 中那些被覆盖的 compareto 方法，我尝试重写这个方法，但是没有成功，因为它没有在比较 t 类型。
这是我的头文件：
我有一个代表列表的类，但我不明白如何使其适用于 T 类型。
例如，在我的 Alist 类中，我有一个名为 "list" 的实例变量，它是类型为 T 的数组，我想在另一个名为 "f()" 的方法内比较这些类型为 T 的对象。
在 public static void 内部：
ListInterface<String> myList = new AList();
myList.add("a");
myList.add("b");
myList.add("c");
myList.f();
在 Alist.java 内部：
public void f() {
System.out.println("a".compareTo("b")); //works
System.out.println(list[1].compareTo(list[2])); //gives the error below
}
对于第二个打印语句，我得到以下错误：
Exception in thread "main" java.lang.Error: Unresolved compilation problem:
The method compareTo(T) is undefined for the type T
英文:
I got this UML, maybe it helps. The only thing I'm using there is
the instance variable T[] list and the method f() which is method just for testing.
(edited)note: Ignore those overrided compareto methods in the UML, I tried to override the method but it didnt work because it was not comparing the t types.
These are my headers:
I have a class that represents a list, but I do not understand how to make it work with T types.
For example in my class Alist I have an instance variable called "list" which is a array of type T, I would like to compare this Type T objects inside another method called "f()" .
inside public static void:
ListInterface<String> myList = new AList();
myList.add("a");
myList.add("b");
myList.add("c");
myList.f();
inside Alist.java:
public void f() {
System.out.println( "a".compareTo("b")); //works
System.out.println(list[1].compareTo(list[2])); //gives the error below
}
For the second print statement I get the error:
Exception in thread "main" java.lang.Error: Unresolved compilation problem:
The method compareTo(T) is undefined for the type T
答案1
得分: 1
如果您想要比较 AList 类的元素，您应该使用泛型类型，就像这样：AList<T extends Comparable<T>> 并对其进行边界限定。
英文:
if you want to compare the elements of AList class you should use your generics type like this AList<T extends Comparable<T>> and bound it.
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