Eclipse中未找到源错误（Java）

Question

我有几行代码：

Set<Group> setofAllGroups;
setofAllGroups = new TreeSet<Group>();
Group[] allGroupsArray = (Group[]) setofAllGroups.toArray();

最后一行导致运行时错误，在调试模式下我得到“Source not found”

类Group的代码：

public class Group 
{
String groupName;
Set<Recipient> groupMembers;

public Group()
{
    groupName = "";
    groupMembers = new TreeSet<Recipient>();
}

public void setGroupName(String name)
{
    groupName = name;
    return;
}

public void addMember(Recipient toAdd)
{
    groupMembers.add(toAdd);
    return;
}
public void addMember(String name, String phoneNumber)
{
    Recipient toAdd = new Recipient(name, phoneNumber);
    groupMembers.add(toAdd);
    return;
}
public void removeMember(Recipient toRemove)
{
    groupMembers.remove(toRemove);
}
public void removeMember(String name, String phoneNumber)
{
    Recipient toRemove = new Recipient(name, phoneNumber);
    groupMembers.remove(toRemove);
}
public void removeAllGroupMembers()
{
    groupMembers.clear();
}

}

运行时错误的原因是什么？

Answer 1

快速回答是你不能这样投：

Group[] allGroupsArray = (Group[]) setofAllGroups.toArray();

相反，你必须使用它：

Group[] allGroupsArray = setofAllGroups.toArray(
     new Group[setofAllGroups.size()]);

那是因为toArray（）返回Object []，之后你尝试将Object []转换为Group []。这失败了。