Number 为何不 Comparable

现状 java 5+

package java.lang.Number
  public abstract class Number implements java.io.Serializable
package java.lang.Integer
  public final class Integer extends Number implements Comparable<Integer>

麻烦
* 直觉上 Number应该是可以 Comparable。
* 接受 Comparable<T> 的方法可以使用 Integer，有时 Integer被包成Number，就不能用了。

讨论
这样有啥不好。

public abstract class XNumber<T extends XNumber<T>> implements java.io.Serializable,Comparable<T>{
    private static final long serialVersionUID = 1L;
}

public final class XLong extends XNumber<XLong>  {
    private static final long serialVersionUID = 1L;

    @Override
    public int compareTo(XLong o) {
        return 0;
    }
}

评论

6 楼 whitesock 2011-02-19  

public final class Float extends Number implements Comparable<Float> {
    public static final float NaN = 0.0f / 0.0f;
    ...
}

final Float nan1 = new Float(Float.NaN);
final Float nan2 = new Float(Float.NaN);
System.out.println(nan1.equals(nan2)); // ture
System.out.println(nan1.compareTo(nan2)); // 0
System.out.println(Float.NaN == Float.NaN); // false

5 楼 trydofor 2011-02-18  

fujohnwang 写道

float and double don't seem comparable

but they are

4 楼 fujohnwang 2011-02-18  

float and double don't seem comparable

3 楼 trydofor 2011-02-18  

http://stackoverflow.com/questions/480632/why-doesnt-java-lang-number-implement-comparable

2 楼 trydofor 2011-02-18  

NOT Comparable Number in JDK
AtomicInteger
AtomicLong

1 楼 trydofor 2011-02-18  

http://zh-cn.w3support.net/index.php?db=so&id=480632