java - Create instance of generic type in Java within the generic class

Question

According to the question, Create instance of generic type in Java?

At the time of writing ,the best answer is found to be...

private static class SomeContainer<E> { 
    E createContents(Class<E> clazz) { 
       return clazz.newInstance(); 
    }
 }

But the answer works only for this SomeContainer.createContents("hello");

My condition is to put the class as an inner class in a generic class,then the code should be like this.

SomeContainer<T>.createContents(T);

That will produce compile time error. There is not any created references for T,also. Is there any way to create completly new T object inside the generic class?

Thanks in advance

Answer 1

由于在 Java 中实现了泛型，您必须传递Class<T>对象以供进一步使用。

这是示例：

public class Outer<E> {

    private static class Inner<E> {
        E createContents(Class<E> clazz) {
            try {
                return clazz.newInstance();
            } catch (InstantiationException | IllegalAccessException e) {
                return null;
            }
        }
    }  

    private Class<E> clazz;
    private Inner<E> inner;

    public Outer(Class<E> clazz) {
        this.clazz = clazz;
        this.inner = new Inner<>();
    }


    public void doSomething() {
        E object = inner.createContents(clazz);
        System.out.println(object);
    }

}

您也可以使用<? extends E>@gparyani在这里提出的