我正在使用
Java 6.
让我的内部类使用相同的泛型类作为它的封闭类.目前我有
public class TernarySearchTree < T > {
...
protected class TSTNode < T > {
// index values for accessing relatives array
protected static final int PARENT = 0,LOKID = 1,EQKID = 2,HIKID = 3;
protected char splitchar;
protected TSTNode < T > [] relatives;
private T data;
protected TSTNode(char splitchar,TSTNode < T > parent) {
this.splitchar = splitchar;
relatives = new TSTNode[4];
relatives[PARENT] = parent;
}
}
}
现在我得到警告
The type parameter T is hiding the type T
如果我从内部类中删除类型参数(即从受保护的类TSTNode< T>行中删除< T>),则在relatives = new TSTNode [4]行上得到一个编译错误.
如何使一切正确？
解决方法
你可以：
>删除< T>来自TSTNode的类型参数(即使其成为非泛型) – 它仍然可以访问外部< T>.
>重命名< T>类TSTNode中的类型参数(说)U.
[UPDATE]
以下是重写代码的四种不同的方法.他们都编译我想你应该考虑使用EnumMap(见下面的第4版).
版本1：在内部类中使用不同命名的类型参数.您需要使用List而不是数组.
public class TernarySearchTree<T> {
protected class TSTNode<U> {
// index values for accessing relatives array:
protected static final int PARENT = 0,HIKID = 3;
protected char splitchar;
protected List<TSTNode<U>> relatives;
private U data;
protected TSTNode(char splitchar,TSTNode<U> parent) {
this.splitchar = splitchar;
relatives = new ArrayList<TSTNode<U>>();
for (int i = 0; i < HIKID; ++i) { // Allocate 4 slots in relatives
relatives.add(null);
}
relatives.set(PARENT,parent);
}
}
private TSTNode<T> node; // When you use it,pass T as U
public TernarySearchTree() {
node = new TSTNode<T>(',',null); // When you use it,pass T as U
}
}
版本2：从封闭类继承T
public class TernarySearchTree<T> {
protected class TSTNode {
// index values for accessing relatives array:
protected static final int PARENT = 0,HIKID = 3;
protected char splitchar;
protected List<TSTNode> relatives;
private T data;
protected TSTNode(char splitchar,TSTNode parent) {
this.splitchar = splitchar;
relatives = new ArrayList<TSTNode>();
for (int i = 0; i < HIKID; ++i) { // Allocate 4 slots in relatives
relatives.add(null);
}
relatives.set(PARENT,parent);
}
}
private TSTNode node;
public TernarySearchTree() {
node = new TSTNode(',null);
}
}
版本3：使用地图(而不是列表)
public class TernarySearchTree<T> {
protected class TSTNode {
// index values for accessing relatives array:
protected static final int PARENT = 0,HIKID = 3;
protected char splitchar;
protected Map<Integer,TSTNode> relatives;
private T data;
protected TSTNode(char splitchar,TSTNode parent) {
this.splitchar = splitchar;
// Create a hash map. No need to pre-allocate!
relatives = new HashMap<Integer,TSTNode>();
relatives.put(PARENT,parent); // set -> put
}
}
private TSTNode node;
public TernarySearchTree() {
node = new TSTNode(',null);
}
}
}
版本4：将索引定义为枚举使用EnunMap(而不是哈希映射)
public class TernarySearchTree<T> {
protected static enum Index {
PARENT,LOKID,EQKID,HIKID;
}
protected class TSTNode {
protected char splitchar;
protected EnumMap<Index,TSTNode parent) {
this.splitchar = splitchar;
// Create an EnumMap.
relatives = new EnumMap<Index,TSTNode>(Index.class);
relatives.put(Index.PARENT,parent);
}
}
private TSTNode node;
public TernarySearchTree() {
node = new TSTNode(',null);
}
}
[更新2]
有一件事要记住：Use EnumMap instead of ordinal indexing