如何返回与使用Java 6传入的类相同类型的对象的实例？ [英] How do I return an instance of an object of the same type as the class passed in using Java 6?

问题描述

我想返回一个与传入的Class对象类型相同的对象的实例。传入的类型可以是ANYTHING。有没有办法与泛型做到这一点？

澄清 - 我不希望方法的调用者不必转换为对象的类例如，

  public Object< Class> getObject（Class class）
 {
 //构造一个Class类型的对象的实例
 
 return object; 
} 
 
 //我想要：
 MyClass myObj = getObject（MyClass.class）; 
 
 //不是（铸造）：
 MyClass myObj =（MyClass）getObject（MyClass.class）; 
  

解决方案

我假设您要创建一个新的实例类。这不可能使用泛型（你不能调用 new T（）），并且使用反射也会受到很大限制。

反射方法可以是：

  // class是一个保留字，所以使用clazz 
公共< T> T getObject（Class< T> clazz）{
 try {
 return clazz.newInstance（）; 
} 
 catch（/ *可由clazz.newInstance（）* /）{
 //处理异常
} 
} $引发的大量异常b $ b  

请注意，这只适用于类没有参数构造函数的情况。

然而，问题出在你为什么需要而不是仅仅调用
new WhatEverClassYouHave（）。

I want to return an instance of an object of same type of the Class object passed in. The type passed in can be ANYTHING. Is there a way to do this with Generics?

To clarify -- I don't want the caller of the method to not have to cast to the Class of the object they passed in

For example,

public Object<Class> getObject(Class class)
{
  // Construct an instance of an object of type Class

  return object;
}

// I want this:
MyClass myObj = getObject(MyClass.class);

// Not this (casting):
MyClass myObj = (MyClass)getObject(MyClass.class);

解决方案

I assume you want to create a new instance of that class. This would not be possible using generics (you can't call new T()) and would also be quite limited using reflection.

The reflection approach could be:

//class is a reserved word, so use clazz
public <T> T getObject(Class<T> clazz) {
  try {
    return clazz.newInstance();
  }
  catch( /*a multitude of exceptions that can be thrown by clazz.newInstance()*/ ) {
    //handle exception
  }
}

Note that this only works if the class has a no-argument constructor.

However, the question would by why you need that instead of just calling
new WhatEverClassYouHave().

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