我正在創建一個通用的多路樹,我知道將只採用四種類型之一(整數,雙精度,字符串和字符)。我在可比接口和插入功能方面遇到問題。下面是相關的代碼到目前爲止,我已經寫了:Multiway樹可比較的接口問題
public class BTree<T extends Comparable<? super T>>
{
private int m=0, height=0, numkeys=0;
private BTreeNode<T> root;
boolean ready=false;
class BTreeNode<T extends Comparable<? super T>>
{
boolean leaf = true;
int keyTally = 1;
Comparable<T> keys[] = new Comparable[m-1];
BTreeNode<T> references[] = new BTreeNode[m];
BTreeNode(T key)
{
keys[0] = (Comparable<T>) key;
for (int i=0; i<m; i++)
references[i] = null;
}
}
public BTree(int c)
{
root=null;
m=c;
}
// Not finished - can't test due to other bug
public boolean insertElement(T elem)
{
insert(elem, root, height);
numkeys++;
return true;
}
// And now the ploblem function
private BTreeNode<T> insert(T elem, BTreeNode<T> node, int hvar)
{
int i;
BTreeNode<T> temp = null;
if (hvar == 0)
{
for (i = 0; i < node.keyTally; i++)
if (elem.compareTo(node.keys[i]) < 0)
break;
}
else
{
for (i = 0; i < node.keyTally; i++)
{
if ((i+1 == node.keyTally) || elem.compareTo(node.keys[i]) < 0)
{
Node n = insert(elem, node.references[i++], hvar-1);
if (n == null)
return null;
temp.keys[0] = n.keys[0];
temp.references[0] = n;
break;
}
}
}
for (int j = node.keyTally; j > i; j--)
node.keys[j] = node.keys[j-1];
node.children[i] = temp;
node.keyTally++;
if (node.keyTally < m)
return null;
else
{
BTreeNode<T> newNode = null;
newNode.keyTally = m/2;
for(i=0; i<m/2; i++)
newNode.references[i] = node.references[m/2+i];
return newNode;
}
return null;
}
,這裏是我的控制檯輸出:
BTree.java:169: error: method compareTo in interface Comparable<T#2> cannot be applied
to given types;
if (elem.compareTo(node.keys[i]) < 0)
^
required: CAP#1
found: Comparable<T#1>
reason: actual argument Comparable<T#1> cannot be converted to CAP#1 by method
invocation conversion
where T#1,T#2 are type-variables:
T#1 extends Comparable<? super T#1> declared in class BTree
T#2 extends Object declared in interface Comparable
where CAP#1 is a fresh type-variable:
CAP#1 extends Object super: T#1 from capture of ? super T#1
BTree.java:176: error: method compareTo in interface Comparable<T#2> cannot be
applied to given types;
if ((i+1 == node.keyTally) || elem.compareTo(node.keys[i]) < 0)
^
required: CAP#1
found: Comparable<T#1>
reason: actual argument Comparable<T#1> cannot be converted to CAP#1 by
method invocation conversion
where T#1,T#2 are type-variables:
T#1 extends Comparable<? super T#1> declared in class BTree
T#2 extends Object declared in interface Comparable
where CAP#1 is a fresh type-variable:
CAP#1 extends Object super: T#1 from capture of ? super T#1
BTree.java:178: error: cannot find symbol
Node n = insert(elem, node.references[i++], hvar-1);
^
symbol: class Node
location: class BTree<T>
where T is a type-variable:
T extends Comparable<? super T> declared in class BTree
BTree.java:191: error: cannot find symbol
node.children[i] = temp;
^
symbol: variable children
location: variable node of type BTree<T>.BTreeNode<T>
where T is a type-variable:
T extends Comparable<? super T> declared in class BTree
Note: Some input files use unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
4 errors
我不明白我在做什麼毛病可比接口,使其抱怨關於compareTo方法。另外,我想知道如果使用字符串類型會做什麼?我認爲它會按字母順序查看哪一個先到達。謝謝:)
謝謝您的回覆!我只需將'elem.compareTo(node.keys [i])'改爲'node.keys [i] .compareTo(elem)' – Tim 2012-04-07 17:35:56