以下是我的简化图表实现
import java.util.ArrayList;
import java.util.List;
public class TreeNode<E extends Comparable<E>> {
private E data;
private List<TreeNode<E>> children;
public TreeNode(E value) {
data = value;
children = new ArrayList<>();
}
public E getData() {
return data;
}
public void setData(E data) {
this.data = data;
}
public List<TreeNode<E>> getChildren() {
return children;
}
public void setChildren(List<TreeNode<E>> children) {
this.children = children;
}
}
我正在编写代码来查找有向图中是否连接了2个节点.我收到编译错误
public static boolean findIfPathExists(TreeNode<? extends Comparable<?>> start,TreeNode<? extends Comparable<?>> end) {
Set<TreeNode<? extends Comparable<?>>> visitednodes = new HashSet<TreeNode<? extends Comparable<?>>>();
return findIfPathExists(start,end,visitednodes);
}
private static boolean findIfPathExists(TreeNode<? extends Comparable<?>> start,TreeNode<? extends Comparable<?>> end,Set<TreeNode<? extends Comparable<?>>> visitednodes) {
if(start == end) return true;
visitednodes.add(start);
List<TreeNode<? extends Comparable<?>>> children = start.getChildren();
for (TreeNode<? extends Comparable<?>> child : children) {
if(visitednodes.contains(child)) continue;
if(findIfPathExists(child,visitednodes)) return true;
}
return false;
}
我在行start.getchildren收到错误
Type mismatch: cannot convert from List<TreeNode<capture #11 -of? extends Comparable<?>>> to List<TreeNode<? extends Comparable<?>>>
解决方法
在方法签名中添加一个类型变量：
public static <T extends Comparable<T>> boolean findIfPathExists(
TreeNode<T> start,TreeNode<T> end) {
private static <T extends Comparable<T>> boolean findIfPathExists(
TreeNode<T> start,TreeNode<T> end,Set<TreeNode<T>> visitednodes) {
然后在你现在的任何地方使用T？扩展Comparable<？>.