如何使Java通用方法静态？ [英] How to make a Java Generic method static?

问题描述

以下是关于如何使Java泛型类将单个项目附加到数组的一段代码。我怎样才能让appendToArray成为一个静态方法。

  public class ArrayUtils< E> {
 
 public E [] appendToArray（E [] array，E item）{
 E [] result =（E []）new Object [array.length + 1]; 
结果[array.length] = item; 
返回结果; 
} 
} 
  

解决方案

只能将签名更改为

  public static< E> E [] appendToArray（E [] array，E item）
  

重要细节：

返回值前面的泛型表达式总是引入（声明）一个新的泛型变量。

另外，类型变量（ ArrayUtils ）和静态方法（ appendToArray ）永远不会相互干扰。

那么，这是什么意思：
在我的回答< E> 中会隐藏 static ，则从 ArrayUtils< E> > E AND < E> 与 ArrayUtils< E>无关 E / code>。

为了更好地反映这个事实，更正确的答案是：

  public static< I> I [] appendToArray（I [] array，I item）
  

The following is a snippet on how to make a java generic class to append a single item to an array. How can I make appendToArray a static method. Adding static to the method signature results in compile errors.

public class ArrayUtils<E> {

        public E[] appendToArray(E[] array, E item) {
            E[] result = (E[])new Object[array.length+1];
            result[array.length] = item;
            return result;
        }
}

解决方案

the only thing you can do is to change your signature to

public static <E> E[] appendToArray(E[] array, E item)

Important details:

Generic expressions preceding the return value always introduce (declare) a new generic type variable.

Additionally, type variables between types (ArrayUtils) and static methods (appendToArray) never interfere with each other.

So, what does this mean: In my answer <E> would hide the E from ArrayUtils<E> if the method wouldn't be static. AND <E> has nothing to do with the E from ArrayUtils<E>.

To reflect this fact better, a more correct answer would be:

public static <I> I[] appendToArray(I[] array, I item)

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