我正在创建一个使用二叉搜索树实现通用 Set 的类。我在我的几个方法中使用了“compareTo”方法,无论我做什么,我都会不断收到规定的警告。感谢您的帮助!
// Allow short name access to following classes
import csc143.data_structures.*;
public class MySet<E> implements SimpleSet<E> {
// the root of the "tree" that structures the set
private BTNode root;
// the current number of elements in the set
private int numElems;
public MySet() {
root = null;
numElems = 0;
}
/**
* Add an element to the set.
*
* @param e The element to be added to the set.
* @return <tt>true</tt> If this operation updated the contents of the set.
*/
public boolean add(E e) {
try {
root = addToSubtree(root, (Comparable) e);
return true;
} catch(DuplicateAdded exc) {
// duplicate trying to be added
return false;
}
}
// This helper method adds the element "e" to tree rooted at r. Returns
// (possibly new) tree containing "e", or throws DuplicateAdded exception
// if "e" already exists in tree.
private BTNode addToSubtree(BTNode r, Comparable elem)
throws DuplicateAdded {
if(r == null) {
return new BTNode(elem);
}
int compare = elem.compareTo(r.item);
// element already in tree
if(compare == 0) {
throw new DuplicateAdded("Element is already in set");
}
if(compare < 0) {
r.left = addToSubtree(r.left, elem);
} else { // compare > 0
r.right = addToSubtree(r.right, elem);
}
// element has been added
return r;
}
/**
* Remove all elements from this set.
*/
public void clear() {
root = null;
numElems = 0;
}
/**
* Checks for the existance of the specified value within the set.
*
* @param e The value sought.
* @return <tt>true</tt> If the value exists in the set.
*/
public boolean contains(E e) {
return subtreeContains(root, (Comparable) e);
}
// This helper method returns whether element "elem" is in
// (sub-)tree with root "r".
private boolean subtreeContains(BTNode r, Comparable elem) {
if(r == null) {
return false;
} else {
int compare = elem.compareTo(r.item);
// found element
if(compare == 0){
return true;
} else if(compare < 0) {
return subtreeContains(r.left, elem);
} else { // compare > 0
return subtreeContains(r.right, elem);
}
}
}
/**
* Check for the existance of elements in the set.
*
* @return <tt>true</tt> If there are no elements in the set.
*/
public boolean isEmpty() {
return root == null;
}
/**
* Return the number of elements in the set.
*
* @return The number of elements in the set.
*/
public int size() {
return numElems;
}
/**
* Returns a String representation of the contents of the set.
*
* @return The String representation of the set.
*/
public String toString() {
}
// this inner class creates the node that compose the binary tree structure
class BTNode<E> {
/**
* The item stored in the node.
*/
public E item;
/**
* The node to the left of "this" node.
*/
public BTNode left;
/**
* The node to the right of "this" node.
*/
public BTNode right;
/**
* Constructs the BTNode object (three parameters).
*
* @param item The item to be stored in the node.
* @param left The node to the left of "this" node.
* @param right The node to the right of "this" node.
*/
@SuppressWarnings("unchecked")
public BTNode(Object item, BTNode left, BTNode right) {
// bind to references
this.item = (E) item;
this.left = left;
this.right = right;
}
/**
* Constructs the BTNode (one parameter).
*
* @param The item to be stored in the node.
*/
public BTNode(Object item) {
// call three parameter constructor
this(item, null, null);
}
}
}
编辑:包括SimpleSet接口(interface):
package csc143.data_structures;
public interface SimpleSet<E> {
/**
* Add an element to the set.
*
* @param e The element to be added to the set.
* @return <tt>true</tt> If this operation updated the contents of the set.
*/
public boolean add(E e);
/**
* Remove all elements from this set.
*/
public void clear();
/**
* Checks for the existance of the specified value within the set.
*
* @param e The value sought.
* @return <tt>true</tt> If the value exists in the set.
*/
public boolean contains(E e);
/**
* Check for the existance of elements in the set.
*
* @return <tt>true</tt> If there are no elements in the set.
*/
public boolean isEmpty();
/**
* Return the number of elements in the set.
*
* @return The number of elements in the set.
*/
public int size();
/**
* Returns a String representation of the contents of the set.
*
* @return The String representation of the set.
*/
public String toString();
}
最佳答案
您方法上的签名使用原始 Comparable
没有泛型的接口(interface)。您的 set 实现中似乎要求数据类型实现 Comparable
, 所以既然你现在使用的是泛型,你应该全面地做出改变。
您没有发布 SimpleSet
的类声明, 所以 Comparable
对 E
的限制可能已经在那里了。如果不是,您需要将类声明更改为:
public class MySet<E extends Comparable<? super E>> implements SimpleSet<E>
这会告诉您的类的客户只有实现 Comparable
的类型允许作为集合实现的泛型类型参数。您没有发布 BTNode
的代码, 但它可能需要在 E
上进行参数化以及 ( BTNode<E>
)。
现在,因为您只允许 E
类型的对象要添加到集合中,您应该更改加法器方法以反射(reflect)这一点:
private BTNode<E> addToSubtree(BTNode<E> r, E elem) throws DuplicateAdded
以此类推,对于subtreeContains
, 等等。 Java泛型的要点是,你用类型占位符( Comparable
代表元素)替换所有这些地方(到 E
,在你的情况下),在编译时限制可以添加的内容,所以废除最需要显式转换。泛型是一个强大但复杂的特性,我推荐阅读 the official tutorial .
关于java - 警告 : unchecked call to compareTo(T) as a member of the raw type java. lang.Comparable,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/18143305/