Java警告：[unchecked]未经检查的转换 [英] Java warning: [unchecked] unchecked conversion

问题描述

我有以下（部分）类：

I have the following (partial) class:

public class Graph<O> {
    private ArrayList<Edge> edges;

    public ArrayList<Edge> getEdges() {
        return edges;
    }
}

现在，当调用方法 getEdges（）>并将结果存储在类型为 ArrayList< Edge> 的变量中，得到警告： [unchecked] unchecked conversion ：

Now, when calling the method getEdges() somewhere else and storing the result in a variable of type ArrayList<Edge>, I get warning: [unchecked] unchecked conversion:

OtherFile.java:101: warning: [unchecked] unchecked conversion
        ArrayList<Edge> edges = graph.getEdges();
                                              ^
  required: ArrayList<Edge>
  found:    ArrayList

我已经看过关于此警告的其他多个问题，但我可以弄清楚我做错了什么。 getEdges（）返回 ArrayList< Edge> ，为什么我不能将它的结果存储在一个精确的变量中类型？

I have looked at multiple other questions about this warning, but I can't figure out what I'm doing wrong. getEdges() returns ArrayList<Edge>, so why can't I store its result in a variable of that exact type?

推荐答案

当您调用 getEdges（）方法对原始类型图。在这种情况下，所有的通用类型都会被其擦除所替代。因此，对于 Graph 原始类型，方法签名变为：

That warning would come when you invoke the getEdges() method on raw type Graph. When that is the case, all the generic types are replaced with their erasure. So, for Graph raw type, the method signature becomes like:

public ArrayList getEdges();

解决方案是使用参数化类型或通配符类型。

Solution is to use parameterized type or wildcard types.

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