Java 类型参数不在类型变量的范围内
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type argument is not within bounds of type-variable
提问by saqehi
Hi Stack Overflow community ^_^
嗨堆栈溢出社区^_^
Basically, I am working with Stacks and converting from Infix to Postfix equations. This is the error message showing on screen when I am trying to compile the Stack class:
基本上，我正在使用堆栈并将中缀转换为后缀方程。这是我尝试编译 Stack 类时在屏幕上显示的错误消息：
Stack.java:5: error: type argument T#1 is not within bounds of type-variable T#2
private LinkedList<T> list;
^
where T#1,T#2 are type-variables:
T#1 extends Object declared in class Stack
T#2 extends Comparable<T#2> declared in class LinkedList
I am having real troubles trying to figure out this error but sadly I don't have a clue of what might be the problem. If I knew a little better I could have provided you with more info.
我在试图找出这个错误时遇到了真正的麻烦，但遗憾的是我不知道可能是什么问题。如果我知道得更好一点，我可以为您提供更多信息。
Thanks in advance for any comments and help!
在此先感谢您的任何意见和帮助！
Update: Here is my class...
更新：这是我的课...
package ListPkg;
public class Stack<T> // implements Comparable<Stack>>
{
private LinkedList<T> list;
public Stack()
{
this("list");
}
public Stack(String name)
{
list = new LinkedList(name);
}
public void push(T item)
{
list.insertAtFront(item);
}
public T pop()
{
list.removeFromFront();
}
public int lenghtIs()
{
return list.lengthIs();
}
public T peek()
{
return list.returnFirstNode();
}
public void print()
{
list.print();
}
public boolean isEmpty()
{
return list.isEmpty();
}
}
回答by Sotirios Delimanolis
It seems you have a class LinkedListdeclared as
看来你有一个类LinkedList声明为
class LinkedList<T extends Comparable<T>> {...}
but you're trying to use it in a class Stackdeclared as
但是您试图在Stack声明为的类中使用它
class Stack<T> {
private LinkedList<T> list;
...
}
The type variable Tdeclared in Stackis completely unrelated to the type variable Tin LinkedList. What's more, they are not compatible. LinkedListexpects a type that is a sub type of Comparable, but Stackis giving it a type argument that has no bounds. The compiler cannot allow this.
该类型变量T的声明Stack是完全无关的类型变量T中LinkedList。更重要的是，它们不兼容。LinkedList期望一个类型是 的子类型Comparable，但是Stack给它一个没有边界的类型参数。编译器不允许这样做。
Add appropriate bounds to your Stackclass' type parameter
为Stack类的类型参数添加适当的边界
class Stack<T extends Comparable<T>> {
