在Java中实例化一个泛型类

在Java中实例化一个泛型类

本文介绍了在Java中实例化一个泛型类的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!

问题描述

我知道Java的泛型与.Net相比有些逊色。我有一个泛型类 Foo< T> ,我真的需要使用无参数的构造函数在 Foo 中实例化 T 。如何解决Java的限制?

解决方案

一个选项是传入 Bar.class (或任何您感兴趣的类型 - 以任何方式指定适当的 Class< T> 引用)并将该值保留为字段:

  public class Test 
{
public static void main(String [] args)
throws Exception //只是为了简单!
{
通用< Bar> x =新的通用< Bar>(Bar.class);
Bar y = x.buildOne();
}
}

public class Generic< T>
{
private Class< T> clazz中;

public Generic(Class< T> clazz)
{
this.clazz = clazz;
}

public T buildOne()抛出InstantiationException,
IllegalAccessException
{
return clazz.newInstance();



public class Bar
{
public Bar()
{
System.out.println(构建);
}
}

另一种选择是有一个工厂并将工厂传递给泛型类的构造函数。这更加灵活,您不必担心反射异常。


I know Java's generics are somewhat inferior to .Net's.

I have a generic class Foo<T>, and I really need to instantiate a T in Foo using a parameter-less constructor. How can one work around Java's limitation?

解决方案

One option is to pass in Bar.class (or whatever type you're interested in - any way of specifying the appropriate Class<T> reference) and keep that value as a field:

public class Test
{
    public static void main(String [] args)
        throws Exception // Just for simplicity!
    {
        Generic<Bar> x = new Generic<Bar>(Bar.class);
        Bar y = x.buildOne();
    }
}

public class Generic<T>
{
    private Class<T> clazz;

    public Generic(Class<T> clazz)
    {
        this.clazz = clazz;
    }

    public T buildOne() throws InstantiationException,
        IllegalAccessException
    {
        return clazz.newInstance();
    }
}

public class Bar
{
    public Bar()
    {
        System.out.println("Constructing");
    }
}

Another option is to have a "factory" interface, and you pass a factory to the constructor of the generic class. That's more flexible, and you don't need to worry about the reflection exceptions.

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08-05 09:17