ClassLoader类findSystemClass()方法 (ClassLoader Class findSystemClass() method)

• findSystemClass() method is available in java.lang package.

  findSystemClass()方法在java.lang包中可用。

• findSystemClass() method is used to find the class with the given binary name and load the class through the system loader if needed.

  findSystemClass()方法用于查找具有给定二进制名称的类，并在需要时通过系统加载器加载该类。

• findSystemClass() method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.

  findSystemClass()方法是一个非静态方法，只能通过类对象访问，如果尝试使用类名称访问该方法，则会收到错误消息。

• findSystemClass() method may throw an exception at the time of finding the class with the given class.

  在使用给定类查找类时， findSystemClass()方法可能会引发异常。

  ClassNotFoundException: This exception may throw when the given class does not exist.

  ClassNotFoundException ：如果给定的类不存在，则可能引发此异常。

Syntax:

句法：

    protected Class findSystemClass(String class_name);

Parameter(s):

参数：

• String class_name – represents the binary name of the class.

  字符串class_name –表示类的二进制名称。

Return value:

返回值：

The return type of this method is Class, it returns a Class object for the given class name.

该方法的返回类型为Class ，它返回给定类名的Class对象。

Example:

例：

// Java program to demonstrate the example 
// of Class findSystemClass(String class_name)
// method of ClassLoader
class FindSystemClass extends ClassLoader {
void loadedSystemClass() throws ClassNotFoundException {
// It checks whether the given class is loaded
// or not by using the findSystemClass()
Class cl1 = super.findSystemClass("java.lang.String");
// If cl1 not null that means cl1 is loaded
// then don't need to load again
if (cl1 != null)
System.out.println("Class already loaded!!!");
else
System.out.println("Ready to load the given class by using system classloader!!!");
}
}
public class Main {
public static void main(String[] args) throws Exception {
// Creating an instance of FindSystemClass
FindSystemClass sc = new FindSystemClass();
sc.loadedSystemClass();
}
}

Output

输出量

Class already loaded!!!

翻译自: https://www.includehelp.com/java/classloader-findsystemclass-method-with-example.aspx