将消费者泛型类型转换为另一种类型
Casting consumer generic type to another type
请先看我的代码。当我想创建一个对象时,我在 BolBFS 构造函数中遇到错误:
Error:
Required type is : Consumer<Node<String, ChildFlightConsignmentInfo>>
Provided type is : Consumer<BolNode>
我知道我不能将 consumer<T>
转换为 consumer\<? extends T>
,但我不知道为什么,我应该如何处理这个问题?
如果我将 Node 更改为 N,我在 adj() 方法中遇到另一个问题 class BFS.
Error:
Required Set<N>
Provided Provided Set<Node<Identifier, Data>>
这是我的代码:
BolBFS.java构造函数:
public BolBFS(TraverseDirection dir, BolNode root, Consumer<BolNode> consumeEachBol, Predicate<BolNode> setFlagCondition, Predicate<BolNode> stopCondition) {
BFS<String, ChildFlightConsignmentInfo, BolNode> bfs = new BFS<>(dir, root, consumeEachBol, setFlagCondition, stopCondition);
}
BolNode.java:
public class BolNode extends Node<String, ChildFlightConsignmentInfo>
BFS.java:
public class BFS<Identifier, Data, N extends Node<Identifier, Data>> implements Serializable {
protected TraverseDirection dir;
protected volatile Queue<Node<Identifier, Data>> nextToVisit;
protected volatile boolean flag;
protected volatile Set<Object> visited;
protected Consumer<Node<Identifier, Data>> consumer;
protected Predicate<Node<Identifier, Data>> checker;
protected Predicate<Node<Identifier, Data>> stopCondition;
protected volatile Map<Object, Node<Identifier, Data>> predecessor;
protected volatile Map<Integer, Set<Node<Identifier, Data>>> levels;
protected volatile Map<Object, Set<Object>> adjList;
protected volatile Map<Object, Node<Identifier, Data>> idMap;
public BFS(TraverseDirection dir, Node<Identifier, Data> root, Consumer<Node<Identifier, Data>> consumer, Predicate<Node<Identifier, Data>> checker, Predicate<Node<Identifier, Data>> stopCondition) { this.dir = dir;
this.flag = false;
this.checker = checker;
this.consumer = consumer;
this.stopCondition = stopCondition;
this.predecessor = new ConcurrentHashMap<>();
this.levels = new ConcurrentHashMap<>();
this.adjList = new ConcurrentHashMap<>();
this.idMap = new ConcurrentHashMap<>();
idMap.put(root.getId(), root);
levels.put(0, Stream.of(root).collect(Collectors.toSet()));
logic(root, consumer, checker, stopCondition);
}
protected Map<TraverseDirection, Set<N>> adj(N node) {
Map<TraverseDirection, Set<N>> result = new ConcurrentHashMap<>();
result.put(TraverseDirection.ANY, node.getChild());
return result;
}
}
Node.class:
public abstract class Node<Identifier, Data> implements Serializable {
public abstract Set<Node<Identifier, Data>> getChild();
}
问题是 Consumer<BolNode>
不是 Consumer<Node<String, ChildFlightConsignmentInfo>>
,原因与 a List<Dog>
is not a List<Animal>
相同。更具体地说,Consumer<BolNode>
期望它总是传递给 BolNode
,而 Consumer<Node<String, ChildFlightConsignmentInfo>>
可能传递给 Node<String, ChildFlightConsignmentInfo>
.[=22 的任何子 class =]
您已在 BFS
class 中声明了类型参数 N extends Node<Identifier, Data>
,但随后未在构造函数参数类型中使用它。我建议尝试:
public BFS(
TraverseDirection dir,
N root,
Consumer<N> consumer, // Or Consumer<? super N>
Predicate<N> checker, // Or Predicate<? super N>
Predicate<N> stopCondition) {
请先看我的代码。当我想创建一个对象时,我在 BolBFS 构造函数中遇到错误:
Error:
Required type is : Consumer<Node<String, ChildFlightConsignmentInfo>>
Provided type is : Consumer<BolNode>
我知道我不能将 consumer<T>
转换为 consumer\<? extends T>
,但我不知道为什么,我应该如何处理这个问题?
如果我将 Node
Error:
Required Set<N>
Provided Provided Set<Node<Identifier, Data>>
这是我的代码:
BolBFS.java构造函数:
public BolBFS(TraverseDirection dir, BolNode root, Consumer<BolNode> consumeEachBol, Predicate<BolNode> setFlagCondition, Predicate<BolNode> stopCondition) {
BFS<String, ChildFlightConsignmentInfo, BolNode> bfs = new BFS<>(dir, root, consumeEachBol, setFlagCondition, stopCondition);
}
BolNode.java:
public class BolNode extends Node<String, ChildFlightConsignmentInfo>
BFS.java:
public class BFS<Identifier, Data, N extends Node<Identifier, Data>> implements Serializable {
protected TraverseDirection dir;
protected volatile Queue<Node<Identifier, Data>> nextToVisit;
protected volatile boolean flag;
protected volatile Set<Object> visited;
protected Consumer<Node<Identifier, Data>> consumer;
protected Predicate<Node<Identifier, Data>> checker;
protected Predicate<Node<Identifier, Data>> stopCondition;
protected volatile Map<Object, Node<Identifier, Data>> predecessor;
protected volatile Map<Integer, Set<Node<Identifier, Data>>> levels;
protected volatile Map<Object, Set<Object>> adjList;
protected volatile Map<Object, Node<Identifier, Data>> idMap;
public BFS(TraverseDirection dir, Node<Identifier, Data> root, Consumer<Node<Identifier, Data>> consumer, Predicate<Node<Identifier, Data>> checker, Predicate<Node<Identifier, Data>> stopCondition) { this.dir = dir;
this.flag = false;
this.checker = checker;
this.consumer = consumer;
this.stopCondition = stopCondition;
this.predecessor = new ConcurrentHashMap<>();
this.levels = new ConcurrentHashMap<>();
this.adjList = new ConcurrentHashMap<>();
this.idMap = new ConcurrentHashMap<>();
idMap.put(root.getId(), root);
levels.put(0, Stream.of(root).collect(Collectors.toSet()));
logic(root, consumer, checker, stopCondition);
}
protected Map<TraverseDirection, Set<N>> adj(N node) {
Map<TraverseDirection, Set<N>> result = new ConcurrentHashMap<>();
result.put(TraverseDirection.ANY, node.getChild());
return result;
}
}
Node.class:
public abstract class Node<Identifier, Data> implements Serializable {
public abstract Set<Node<Identifier, Data>> getChild();
}
问题是 Consumer<BolNode>
不是 Consumer<Node<String, ChildFlightConsignmentInfo>>
,原因与 a List<Dog>
is not a List<Animal>
相同。更具体地说,Consumer<BolNode>
期望它总是传递给 BolNode
,而 Consumer<Node<String, ChildFlightConsignmentInfo>>
可能传递给 Node<String, ChildFlightConsignmentInfo>
.[=22 的任何子 class =]
您已在 BFS
class 中声明了类型参数 N extends Node<Identifier, Data>
,但随后未在构造函数参数类型中使用它。我建议尝试:
public BFS(
TraverseDirection dir,
N root,
Consumer<N> consumer, // Or Consumer<? super N>
Predicate<N> checker, // Or Predicate<? super N>
Predicate<N> stopCondition) {