编写一个泛型方法来复制一个数组 [英] Write a generic method to copy an array

问题描述

对于我的编程任务，我被要求编写一个通用的复制方法来从一个数组复制到一个相同大小和类型的数组.这在Java中甚至可能吗?我尝试的一切都以一些通用数组创建"错误告终.我迷路了，不知道如何解决这个问题！

For my programming assignment, I was asked to write a generic copy method to copy from one array to an identically sized and typed array. Is this even possible in Java? Everything I tried ended up with some "generic array creation" error. I am lost and don't know how to solve this problem!

public class copyArray<AnyType>{

   public copyArray(AnyType[] original){ 

     AnyType[] newarray = new AnyType[original.length];  

     for(int i =0; i<original.length; i++){ 
        newarray[i] = original[i]; } 
}

推荐答案

可以使用反射的概念编写一个可以在运行时判断类型的泛型复制方法.简而言之，反射是在运行时检查类、接口、字段和方法的能力，而无需在编译时知道类、方法等的名称.

You can use the concept of reflection to write a generic copy method that can determine type at runtime. In a nutshell, reflection is the ability to inspect classes, interfaces, fields and methods at runtime without knowing the names of classes, methods etc at compile time.

java.lang.Reflect 与 java.lang.Class 组成 Java 反射 API.这个方法使用这两个类和它们的一些方法来创建一个通用的 arrayCopy 方法，它将为我们找出类型.

java.lang.Reflect together with java.lang.Class comprise the Java Reflection API. This method uses both of those classes and some of their methods to make a generic arrayCopy method that will find out the type for us.

更多信息:什么是反射，为什么它有用?

Class<?> 使用通配符运算符 ? 基本上说我们可以有一个未知的 Class 对象type - 类 Class 的通用版本.

<T> 是一个通用运算符，代表 原始类型

ArrayArray 类提供静态方法来动态创建和访问Java 数组.即，此类包含允许您设置和查询数组元素的值、确定数组的长度以及创建新的数组实例的方法.我们将使用 Array.newInstance()

Class<?> is using a wildcard operator ? which basically says that we can have a Class object of unknown type - a generic version of class Class.

<T> is a generic operator that stands for raw type

ArrayThe Array class provides static methods to dynamically create and access Java arrays. i.e. This class contains methods that allow you to set and query the values of array elements, determine the length of the array, and create new instances of arrays. We are going to use Array.newInstance()

getClass () - 返回一个数组，其中包含代表所有公共类和接口的 Class 对象，这些公共类和接口是所表示的类对象的成员.

getComponentType() - 返回表示数组的组件类型(什么类型，即 int 等)的类.

newInstance() - 获取数组的新实例.

getClass () - returns an array containing Class objects representing all public classes and interfaces that are members of the represented class object.

getComponentType() - returns the class representing the component type (what type i.e. int, , etc) of the array.

newInstance() - Gets a new instance of an array.

private <T> T[] arrayCopy(T[] original) {

    //get the class type of the original array we passed in and determine the type, store in arrayType
    Class<?> arrayType = original.getClass().getComponentType();

    //declare array, cast to (T[]) that was determined using reflection, use java.lang.reflect to create a new instance of an Array(of arrayType variable, and the same length as the original
    T[] copy = (T[])java.lang.reflect.Array.newInstance(arrayType, original.length);

    //Use System and arraycopy to copy the array
    System.arraycopy(original, 0, copy, 0, original.length);
    return copy;
}

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