使用接受字符串参数的构造函数实例化一个类对象? [英] Instantiate a class object with constructor that accepts a string parameter?

问题描述

我想从它的 Class 对象实例化一个对象，使用接受单个 String 参数的构造函数.

I would like to instantiate an object from its Class object, using the constructor that accepts a single String argument.

这是一些接近我想要的代码:

Here is some code that approaches what I want:

Object object = null;
Class classDefinition = Class.forName("javax.swing.JLabel");
object = classDefinition.newInstance();

然而，它实例化了没有文本的 JLabel 对象.我想使用接受字符串作为初始文本的 JLabel 构造函数.有没有办法从 Class 对象中选择特定的构造函数?

However, it instantiates the JLabel object with no text. I would like to use the JLabel constructor that accepts a string as the initial text. Is there a way to select a specific constructor from a Class object?

推荐答案

Class.newInstance 调用无参数构造函数(不带任何参数的构造函数).为了调用不同的构造函数，您需要使用反射包(java.lang.reflect).

Class.newInstance invokes the no-arg constructor (the one that doesn't take any parameters). In order to invoke a different constructor, you need to use the reflection package (java.lang.reflect).

像这样获取一个 Constructor 实例:

Get a Constructor instance like this:

Class<?> cl = Class.forName("javax.swing.JLabel");
Constructor<?> cons = cl.getConstructor(String.class);

对 getConstructor 的调用指定您需要采用单个 String 参数的构造函数.现在创建一个实例:

The call to getConstructor specifies that you want the constructor that takes a single String parameter. Now to create an instance:

Object o = cons.newInstance("JLabel");

大功告成.

附言仅将反射作为最后的手段！

P.S. Only use reflection as a last resort!

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