java泛型 - 类型Comparable< capture＃1-of？>中的方法compareTo（capture＃1 of？）>不适用于论据 [英] java generics - The method compareTo(capture#1-of ?) in the type Comparable<capture#1-of ?> is not applicable for the arguments

问题描述

所以我想这样做：

  public interface IFieldObject {
 public Comparable get（）; 
} 
 
 public interface IFieldCondition {
 public boolean apply（IFieldObject field，Comparable compare）; 
 
 $ b $ public class EqualTo implements IFieldCondition {
 public boolean apply（IFieldObject field，Comparable compare）{
 return（field.get（）。compareTo（compare） == 0）; 
} 
} 
  

但Eclipse给了我警告：

类型安全性：方法compareTo（Object）属于原始
类型Comparable。参考通用的
类型Comparable应该是
参数化的

所以我把它变成了：

  public interface IFieldObject {
 public Comparable<？>得到（）; 
} 
 
 public interface IFieldCondition {
 public boolean apply（IFieldObject field，Comparable<？> compare）; 
} 
 
 public class EqualTo implements IFieldCondition {
 public boolean apply（IFieldObject field，Comparable<？> compare）{
 return（field.get（）。 compareTo（compare）== 0）; 
 
 
  

由于以下原因而无法编译：

类型Comparable
中的方法compareTo（capture＃1 of？）
不适用于参数
（可比较）

有什么正确的方法可以做到这一点？
（无惯性Java> = 1.6的警告）

解决方案

这个怎么样？

  public interface IFieldObject {
 public< T>可比< T>得到（）; 
} 
 
 public interface IFieldCondition {
 public boolean apply（IFieldObject field，Comparable<？> compare）; 
} 
 
 public class EqualTo implements IFieldCondition {
 public boolean apply（IFieldObject field，Comparable<？> compare）{
 return（field.get（）。 compareTo（compare）== 0）; 
} 
} 
  

So I want to do this:

public interface IFieldObject {
    public Comparable get();
}

public interface IFieldCondition {
    public boolean apply(IFieldObject field, Comparable compare);
}

public class EqualTo implements IFieldCondition {
    public boolean apply(IFieldObject field, Comparable compare) {
        return (field.get().compareTo(compare) == 0);       
    }    
}

but Eclipse gives me warnings:

Type safety: The method compareTo(Object) belongs to the raw type Comparable. References to generic type Comparable should be parameterized

So I turned this into:

public interface IFieldObject {
    public Comparable<?> get();
}

public interface IFieldCondition {
    public boolean apply(IFieldObject field, Comparable<?> compare);
}

public class EqualTo implements IFieldCondition {
    public boolean apply(IFieldObject field, Comparable<?> compare) {
        return (field.get().compareTo(compare) == 0);       
    }
}

which does not compile because of:

The method compareTo(capture#1-of ?) in the type Comparable is not applicable for the arguments (Comparable)

What's the right way to do that ? (without warnings following idiomatic Java >= 1.6)

解决方案

How about this?

public interface IFieldObject {
    public<T> Comparable<T> get();
}

public interface IFieldCondition {
    public boolean apply(IFieldObject field, Comparable<?> compare);
}

public class EqualTo implements IFieldCondition {
    public boolean apply(IFieldObject field, Comparable<?> compare) {
        return (field.get().compareTo(compare) == 0);       
    }
}

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