Java 从字符串获取类类型
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Getting Class type from String
提问by Steven
I have a Stringwhich has a name of a class say "Ex"(no .classextension). I want to assign it to a Classvariable, like this:
我有一个String类的名称说"Ex"（没有.class扩展名）。我想将它分配给一个Class变量，如下所示：
Class cls = (string).class
How can i do that?
我怎样才能做到这一点？
采纳答案by Bozho
Class<?> cls = Class.forName(className);
But your classNameshould be fully-qualified - i.e. com.mycompany.MyClass
但你className应该是完全合格的 - 即com.mycompany.MyClass
回答by Hans Westerbeek
It should be:
它应该是：
Class.forName(String classname)
Class.forName(String classname)
回答by Manrico Corazzi
Not sure what you are asking, but... Class.forname, maybe?
不确定你在问什么，但是... Class.forname，也许？
回答by rsp
You can use the forNamemethod of Class:
您可以使用以下forName方法Class：
Class cls = Class.forName(clsName);
Object obj = cls.newInstance();
回答by JuanZe
String clsName = "Ex"; // use fully qualified name
Class cls = Class.forName(clsName);
Object clsInstance = (Object) cls.newInstance();
Check the Java Tutorial trail on Reflection at http://java.sun.com/docs/books/tutorial/reflect/TOC.htmlfor further details.
在http://java.sun.com/docs/books/tutorial/reflect/TOC.html上查看有关反射的 Java 教程路径以获取更多详细信息。
回答by gmhk
You can get the Class reference of any class during run time through the Java Reflection Concept.
您可以在运行时通过 Java 反射概念获取任何类的 Class 引用。
Check the Below Code. Explanation is given below
检查下面的代码。解释如下
Here is one example that uses returned Class to create an instance of AClass:
下面是一个使用返回的 Class 创建 AClass 实例的示例：
package com.xyzws;
class AClass {
public AClass() {
System.out.println("AClass's Constructor");
}
static {
System.out.println("static block in AClass");
}
}
public class Program {
public static void main(String[] args) {
try {
System.out.println("The first time calls forName:");
Class c = Class.forName("com.xyzws.AClass");
AClass a = (AClass)c.newInstance();
System.out.println("The second time calls forName:");
Class c1 = Class.forName("com.xyzws.AClass");
} catch (ClassNotFoundException e) {
// ...
} catch (InstantiationException e) {
// ...
} catch (IllegalAccessException e) {
// ...
}
}
}
The printed output is
打印的输出是
The first time calls forName:
static block in AClass
AClass's Constructor
The second time calls forName:
The class has already been loaded so there is no second "static block in AClass"
该类已经加载，因此没有第二个“AClass 中的静态块”
The Explanation is below
解释如下
Class.ForName is called to get a Class Object
调用 Class.ForName 获取类对象
By Using the Class Object we are creating the new instance of the Class.
通过使用类对象，我们正在创建类的新实例。
Any doubts about this let me know
对此有任何疑问让我知道
