package test.test_5;
class Person {
//...
}
class Student extends Person {
//...
}
public class test_5 {
public static void main(String[] args) throws ClassNotFoundException {
//方式一
Class<Person> clazz1 = Person.class;
System.out.println("clazz1 = " + clazz1); //clazz1 = class test.test_5.Person
//方式二
Person p1 = new Person();
Class<? extends Person> clazz2 = p1.getClass(); //因为p1有可能是多态性，所以泛型使用extends方式
System.out.println("clazz2 = " + clazz2); //clazz2 = class test.test_5.Person
Person p2 = new Student();
Class<? extends Person> clazz3 = p2.getClass(); //多态性
System.out.println("clazz3 = " + clazz3); //clazz3 = class test.test_5.Student
//方式三
Class<?> clazz4 = Class.forName("test.test_5.Person"); //因为此时无法确定forName()参数的类型，所以Class的泛型是‘?’，参数内需使用”完整包名+类名“
System.out.println("clazz4 = " + clazz4); //clazz4 = class test.test_5.Person
clazz4 = Class.forName("java.lang.String"); //可以转换Class类型
System.out.println("clazz4 now = " + clazz4); //clazz4 now = class java.lang.String
//方式四
ClassLoader classLoader = test_5.class.getClassLoader();
Class<?> clazz5 = classLoader.loadClass("test.test_5.Student");
System.out.println("clazz5 = " + clazz5); //clazz5 = class test.test_5.Student
/*
clazz1：class test.test_5.Person
clazz2：class test.test_5.Person
clazz3：class test.test_5.Student
clazz4：从 class test.test_5.Person 转换到 class java.lang.String
clazz5；class test.test_5.Student
*/
//比较四种方式的Class是不是同一类
System.out.println("(clazz1 == clazz2) is " + (clazz1 == clazz2)); //true
System.out.println("(clazz1 == clazz3) is " + (clazz1 == clazz3)); //false
System.out.println("(clazz1 == clazz4) is " + (clazz1 == clazz4)); //false，因为clazz4被转换了
System.out.println("(clazz1 == clazz5) is " + (clazz1 == clazz5)); //false
System.out.println("(clazz3 == clazz5) is " + (clazz3 == clazz5)); //true
}
}
运行结果：
clazz1 = class test.test_5.Person
clazz2 = class test.test_5.Person
clazz3 = class test.test_5.Student
clazz4 = class test.test_5.Person
clazz4 now = class java.lang.String
clazz5 = class test.test_5.Student
(clazz1 == clazz2) is true
(clazz1 == clazz3) is false
(clazz1 == clazz4) is false
(clazz1 == clazz5) is false
(clazz3 == clazz5) is true
