创建一个compareTo实现可比较的通用类 [英] Create a compareTo to a Generic Class that Implements Comparable

问题描述

我有一个具有两个类型变量的泛型类，它们实现java.lang.Comparable。

 
 public class DoubleKey< K，J> ;实现可比< DoubleKey< K，J>> {
 
 private K key1; 
私人J key2; 
 
 public DoubleKey（K key1，J key2）{
 this.key1 = key1; 
 this.key2 = key2; 
} 
 
 public K getFirstKey（）{
 return this.key1; 
} 
 
 public J getSecondKey（）{
 return this.key2; 
} 
 
 //需要比较接口
 public int compareTo（DoubleKey< K，J> aThat）{
 ... 
} 
 
 
 
 
 
因为我用Comparable实现它，所以我需要编写compareTo（）方法。因为K，J可以是 ANY 类型，所以我在如何完全比较它们时遇到问题。有没有办法在比较中捕捉所有可能的类型（Primitive，Wrapper，Object）？感谢您的帮助！
解决方案
所以总结一下上面的内容， p> 
 
 
  public class DoubleKey< K extends Comparable< K>，J extends Comparable< J>> 
实现了Comparable< DoubleKey< K，J>> {
 
 private K key1; 
私人J key2; 
 
 public DoubleKey（K key1，J key2）{
 this.key1 = key1; 
 this.key2 = key2; 
} 
 
 public K getFirstKey（）{
 return this.key1; 
} 
 
 public J getSecondKey（）{
 return this.key2; 
 
 $ b $ public int compareTo（DoubleKey< K，J> that）{
 
 int cmp = this.getFirstKey（）。compareTo（that.getFirstKey（） ）; 
 if（cmp == 0）
 cmp = this.getSecondKey（）。compareTo（that.getSecondKey（））; 
 return cmp; 
} 
} 
  
 
I have a Generic Class with two type variables, which implements java.lang.Comparable.
public class DoubleKey<K,J> implements Comparable<DoubleKey<K,J>>{

    private K key1;
    private J key2;

    public DoubleKey(K key1, J key2){
        this.key1 = key1;
        this.key2 = key2;
    } 

    public K getFirstKey(){
        return this.key1;
    }

    public J getSecondKey(){
        return this.key2;
    }

    // need for Comparable interface
    public int compareTo(DoubleKey<K,J> aThat){
        ...
    }

}
Becuase i implemeted it with Comparable, I need to write the compareTo() method. Because K, J can be of ANY type, I'm having problems on how to compare them completely. Is there a way to be able to catch all possible types (Primitive, Wrapper, Object) in the comparison? Thanks for the help!
解决方案
so to summarize the said above and to puzzle it together into a working code this is:    
    public class DoubleKey<K extends Comparable<K>, J extends Comparable<J>>
        implements Comparable<DoubleKey<K, J>> {

    private K key1;
    private J key2;

    public DoubleKey(K key1, J key2) {
        this.key1 = key1;
        this.key2 = key2;
    }

    public K getFirstKey() {
        return this.key1;
    }

    public J getSecondKey() {
        return this.key2;
    }

    public int compareTo(DoubleKey<K, J> that) {

        int cmp = this.getFirstKey().compareTo(that.getFirstKey());
        if (cmp == 0)
            cmp = this.getSecondKey().compareTo(that.getSecondKey());
        return cmp;
    }
}


                        
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