[英]Generic setter method incompatible type error
我是泛型的新手,我正在嘗試使用泛型SinglyLinkedNode實現鏈表。 但是,當我運行setData()和setNext()方法時,出現以下錯誤:
.\singlyLinkedList\SinglyLinkedNode.java:13: error: incompatible types: T#1 cannot be
converted to T#2
this.data = d;
^
where T#1,T#2 are type-variables:
T#1 extends Object declared in method <T#1>setData(T#1)
T#2 extends Object declared in class SinglyLinkedNode
.\singlyLinkedList\SinglyLinkedNode.java:21: error: incompatible types:
SinglyLinkedNode<T#1> cannot be converted to SinglyLinkedNode<T#2>
this.next = n;
^
where T#1,T#2 are type-variables:
T#1 extends Object declared in method <T#1>setNext(SinglyLinkedNode<T#1>)
T#2 extends Object declared in class SinglyLinkedNode
在我看來,引發該錯誤是因為存在潛在的情況,其中預先存在的this.data或this.next的類型與d或n不匹配。 我該如何解決? 有什么辦法可以用T#2(新數據)覆蓋T#1(現有數據)的類型? 這是帶有構造函數和設置方法的類:
public class SinglyLinkedNode<T> {
private T data;
private SinglyLinkedNode<T> next;
SinglyLinkedNode(T d) {
this.data = d;
this.next = null;
}
public <T> void setData(T d) {
this.data = d;
}
//...
public <T> void setNext(SinglyLinkedNode<T> n) {
this.next = n;
}
//...
}
感謝您提供的任何幫助。 提前致謝!
編輯:感謝您的幫助! 我已從方法中刪除,但是從SinglyLinkedList類運行setNext()時仍然出現以下錯誤:
.\singlyLinkedList\SinglyLinkedList.java:63: error: method setNext in class SinglyLinkedNode<T#2> cannot be applied to given types;
curr.setNext() = toBeRemoved.getNext();
^
required: SinglyLinkedNode<T#1>
found: no arguments
reason: actual and formal argument lists differ in length
where T#1,T#2 are type-variables:
T#1 extends Object declared in class SinglyLinkedList
T#2 extends Object declared in class SinglyLinkedNode
.\singlyLinkedList\SinglyLinkedList.java:79: error: method setNext in class SinglyLinkedNode<T#2> cannot be applied to given types;
prev.setNext() = this.head;
^
required: SinglyLinkedNode<T#1>
found: no arguments
reason: actual and formal argument lists differ in length
where T#1,T#2 are type-variables:
T#1 extends Object declared in class SinglyLinkedList
T#2 extends Object declared in class SinglyLinkedNode
.\singlyLinkedList\SinglyLinkedList.java:82: error: method setNext in class SinglyLinkedNode<T#2> cannot be applied to given types;
prev.setNext() = curr.getNext();
^
required: SinglyLinkedNode<T#1>
found: no arguments
reason: actual and formal argument lists differ in length
where T#1,T#2 are type-variables:
T#1 extends Object declared in class SinglyLinkedList
T#2 extends Object declared in class SinglyLinkedNode
因此,在我看來,getNext()(來自SinglyLinkedNode)和head(來自SinglyLinkedList)似乎沒有返回任何值,即使它們都應返回SinglyLinkedNode對象也是如此。
這是有問題的代碼。 我已標記出錯誤發生的位置。
public class SinglyLinkedList<T> {
private int size;
private SinglyLinkedNode<T> head;
private SinglyLinkedNode<T> tail;
SinglyLinkedList() {
this.size = 0;
this.head = null;
this.tail = null;
}
//...
public SinglyLinkedNode<T> remove(int i) {
SinglyLinkedNode<T> curr = this.head;
for(int counter = 0; counter < i; counter++) {
curr = curr.getNext(); //<---------------
}
SinglyLinkedNode<T> toBeRemoved = curr.getNext();
curr.setNext() = toBeRemoved.getNext();
this.size--;
return toBeRemoved;
}
//...
public SinglyLinkedNode<T> remove(T d) {
if(this.head == null) {
return null;
}
if(this.head.getData() == d) {
SinglyLinkedNode<T> toBeRemoved = this.head;
this.head = this.head.getNext();
return toBeRemoved;
}
SinglyLinkedNode<T> curr = this.head;
SinglyLinkedNode<T> prev = null;
prev.setNext() = this.head; //<---------------
while(curr.getNext() != null) {
if(curr.getData() == d) {
prev.setNext() = curr.getNext(); //<---------------
return curr;
}
}
return null;
}
//...
如果仍然有人遇到這篇文章,如果他們能幫助我,我將不勝感激。 再次感謝!
編輯:我也修復此錯誤; 它的
curr.setNext(toBeRemoved.getNext());
不
curr.setNext() = toBeRemoved.getNext()
您面臨的問題實際上非常簡單。 基本上,您需要了解泛型方法完全獨立於泛型類 。
public <T> void setData(T d) {
this.data = d;
}
public <T> void setNext(SinglyLinkedNode<T> n) {
this.next = n;
}
將<T>
放在方法的修飾符中時,即表示它是通用方法。 泛型方法中的類型T不同,並且覆蓋了整個類的類型T,這意味着您可以輸入任何類型的對象,並且該方法會將其用作其局部T值,該值可能與全局值完全不同類型T。
從方法修飾符中刪除<T>
將使它們成為常規的setter方法,並且默認為類類型T,該類型必須保證與所需類型匹配。
您不需要在setter上具有泛型,因為它將處理與類所處理的相同類型的數據。 因此,您的代碼將如下所示:
public class SinglyLinkedNode<T> {
private T data;
private SinglyLinkedNode<T> next;
SinglyLinkedNode(T d) {
this.data = d;
this.next = null;
}
public void setData(T d) {
this.data = d;
}
//...
public void setNext(SinglyLinkedNode<T> n) {
this.next = n;
}
//...
}
因此,現在您可以創建SinglyLinkedNode實例,並將值設置為:
public static void main(String[] args) {
SinglyLinkedNode<Integer> integers = new SinglyLinkedNode<>(2);
//
}
另外,由於我已經有一個設置值的構造函數,因此我將擺脫設置方法。
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