java - Eclipse (Java) 中未找到源错误

Question

我有这几行代码:

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

最后一行导致运行时错误，在 Debug模式下我得到“找不到源”

Group 类的代码:

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转换:

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

相反，你必须使用这个:

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

这是因为 toArray() 返回 Object[]，然后您尝试将 Object[] 转换为 Group[]。这失败了。