ClassLoader類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()方法用于查找具有給定二進制名稱的類，并在需要時通過系統加載器加載該類。

• 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()方法是一個非靜態方法，只能通過類對象訪問，如果嘗試使用類名稱訪問該方法，則會收到錯誤消息。

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

  在使用給定類查找類時， findSystemClass()方法可能會引發異常。

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

  ClassNotFoundException ：如果給定的類不存在，則可能引發此異常。

Syntax:

句法：

    protected Class findSystemClass(String class_name);

Parameter(s):

參數：

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

  字符串class_name –表示類的二進制名稱。

Return value:

返回值：

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

該方法的返回類型為Class ，它返回給定類名的Class對象。

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

輸出量

Class already loaded!!!

翻譯自: https://www.includehelp.com/java/classloader-findsystemclass-method-with-example.aspx