java Comparator<String> 必须覆盖超类方法
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Comparator<String> must override super class method
提问by Kenny Wyland
I'm making a TreeMap<String, String>and want to order it in a descending fashion. I created the following comparator:
我正在制作一个TreeMap<String, String>并希望以降序方式订购它。我创建了以下比较器：
Comparator<String> descender = new Comparator<String>() {
@Override
public int compare(String o1, String o2) {
return o2.compareTo(o1);
}
};
I construct the TreeMap like so:
我像这样构造 TreeMap：
myMap = new TreeMap<String, String>(descender);
myMap = new TreeMap<String, String>(descender);
However, I'm getting the following error:
但是，我收到以下错误：
The method compare(String, String) of type new Comparator<String>(){} must override a superclass method
I've never fully groked generics, what am I doing wrong?
我从来没有完全理解泛型，我做错了什么？
回答by BalusC
Your Eclipse project is apparently set to Java 1.5. The @Overrideannotation is then indeed not supported on interface methods. Either remove that annotation or fix your project's compliance level to Java 1.6.
您的 Eclipse 项目显然设置为 Java 1.5。@Override接口方法确实不支持该注释。删除该注释或将项目的合规性级别修复为 Java 1.6。
回答by Philipp Reichart
You don't need to write a custom Comparatorif you just want to reverse the natural (ascending) ordering.
Comparator如果您只想反转自然（升序）排序，则无需编写自定义。
To get a descending ordering just use:
要获得降序，只需使用：
myMap = new TreeMap<String, String>(java.util.Collections.reverseOrder());
回答by Kenny Wyland
Ah, I found the problem. When instantiating a new anonymous instance of a Comparable, I'm not overriding the interfaces methods... I'm implementing them. The @Override directive was the problem. The compare() method wasn't overriding an existing method, it was implementing part of the interface. I copied that code from another place and it shouldn't have had the @Override.
啊，我发现问题了。在实例化 Comparable 的新匿名实例时，我没有覆盖接口方法......我正在实现它们。@Override 指令是问题所在。compare() 方法没有覆盖现有方法，它实现了接口的一部分。我从另一个地方复制了那个代码，它不应该有@Override。
