Java Generics有没有采用需要实现2个接口的Generic参数的方法？ [英] Is there a way with Java Generics to take Generic parameter that requires implementation of 2 interfaces?

问题描述

说我有这个代码 -

  public interface ParentInterface1 {
 public List< ;?扩展ChildInterface1>的getChildren（）; 
 public void setChildren（List< ;? extends ChildInterface1> children）; 
} 
 public interface ParentInterface2 {
 public List< ;?扩展ChildInterface2>的getChildren（）; 
 public void setChildren（List< ;? extends ChildInterface2> children）; 
} 
 public interface ChildInterface1 {
 public String getField（）; 
 public void setField（String field）; 
} 
 public interface ChildInterface2 {
 public String getField（）; 
 public void setField（String field）; 
} 
公共类LParentImpl实现ParentInterface1，ParentInterface2 {
 private List< ChildImpl>列表; 
 public List< ChildImpl> getChildren（）{
返回列表; 
} 
 public void setChildren（List< ...想要接受ChildImpl，其中
实现ChildInterface1和ChildInterface2>子元素）{
抛出新的UnsupportedOperationException（还不支持。 ）; 
} 
} 
 public class ChildImpl implements ChildInterface1，ChildInterface2 {
 private String field; 
 public String getField（）{
 return field; 
} 
 public void setField（String field）{
 this.field = field; 
 
 
 
 
 
 
 $ b $ p有没有办法让setChildren（）在ParentImpl类可以工作，而不需要从接口和实现中完全删除泛型类型？
 
 
 
我想做类似于 -  
  public void setChildren（List <？extends ChildInterface1& ChildInterface2> children）
  
这种接口/实现结构对于非泛型类型是有效的，但是似乎泛型的运行时擦除的某些方面可能会使这不可能？或者我错过了一些神奇的语法？
 
 
 
编辑：使用列表< ;?延伸ChildInterface1& ChildInterface2>产生这个编译错误 -  
  ... \ParentImpl.java：20：>预计
 public void setChildren（List <？extends ChildInterface1& ChildInterface2> children）{
  
 
 
解决方案
您的问题没有意义。
 
 
 
  ParentInterface1.setChildren 接受列表与LT; ChildInterface1> 。因此，这么多 LParentImpl.setChildern ，但是你正试图限制它，所以它不会。
 
 
 
你可能会想要说，parameterise  ParentInterface1  /  2 ，但我建议避免多接口的继承接口涉及泛型）。 
Say I have this code - 
public interface ParentInterface1 {
    public List<? extends ChildInterface1> getChildren();
    public void setChildren(List<? extends ChildInterface1> children);
}
public interface ParentInterface2 {
    public List<? extends ChildInterface2> getChildren();
    public void setChildren(List<? extends ChildInterface2> children);
}
public interface ChildInterface1 {
    public String getField();
    public void setField(String field);
}
public interface ChildInterface2 {
    public String getField();
    public void setField(String field);
}
public class LParentImpl implements ParentInterface1, ParentInterface2 {
    private List<ChildImpl> list;
    public List<ChildImpl> getChildren() {
        return list;
    }
    public void setChildren(List<... wants to accept ChildImpl, which 
                                   implements ChildInterface1 & ChildInterface2> children) {
        throw new UnsupportedOperationException("Not supported yet.");
    }
}
public class ChildImpl implements ChildInterface1, ChildInterface2 {
    private String field;
    public String getField() {
        return field;
    }
    public void setField(String field) {
        this.field = field;
    }
}
Is there a way to make the setChildren() in the ParentImpl class work, without removing the Generic typing completely from the interfaces and implementation?

I'd like to do something like - 
public void setChildren(List<? extends ChildInterface1 & ChildInterface2> children) 
This sort of interface/implementation structure is valid for non Generic types, but it seems some aspect of the run-time erasure of Generics might make this impossible? Or am I missing some magic syntax?

Edit: Using the List<? extends ChildInterface1 & ChildInterface2> yields this compile error - 
...\ParentImpl.java:20: > expected
    public void setChildren(List<? extends ChildInterface1 & ChildInterface2> children) {

解决方案
Your problem doesn't makes sense.

ParentInterface1.setChildren accepts List<ChildInterface1>. Therefore so much LParentImpl.setChildern, but you are trying to constrain it so that it does not.

You might want to say, parameterise ParentInterface1/2, but I'd suggest avoiding multiple inheritance of interface wherever possible (not just where generics are involved).

                        
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