Java Class isAssignableFrom()方法及示例

java.lang.Class类的isAssignableFrom()方法用于检查指定类的对象是否可以分配给该类的实例。如果两个类都是相同的，或者指定的类是超类或超接口，那么它将是兼容的。如果指定的类的对象可以被赋值到这个类的实例中，该方法返回true。否则会返回false。

语法。

public boolean isAssignableFrom(Class<T> class)

参数。该方法接受class作为参数，它是指定的类，其对象要检查与该类实例的兼容性。

返回值。如果指定的类的对象可以被投到这个类的实例中，这个方法返回true。否则返回false。

下面的程序演示了isAssignableFrom()方法。

例1:

// Java program to demonstrate isAssignableFrom() method
  
public class Test {
    public static void main(String[] args)
        throws ClassNotFoundException
    {
  
        // returns the Class object for this class
        Class myClass = Class.forName("Test");
  
        System.out.println("Class represented by myClass: "
                           + myClass.toString());
  
        // get the Class instance using forName() method
        Class c = Class.forName("java.lang.String");
  
        System.out.println("Class represented by c: "
                           + c.toString());
  
        // Check if object c is compatible
        // using isAssignableFrom() method
        System.out.println("Is c compatible: "
                           + myClass.isAssignableFrom(c));
    }
}

输出:

Class represented by myClass: class Test
Class represented by c: class java.lang.String
Is c compatible: false

例2:

// Java program to demonstrate isAssignableFrom() method
  
public class Test {
    public static void main(String[] args)
        throws ClassNotFoundException
    {
  
        // returns the Class object for this class
        Class myClass = Class.forName("Test");
  
        System.out.println("Class represented by myClass: "
                           + myClass.toString());
  
        // get the Class instance using forName() method
        Class c = Class.forName("Test");
  
        System.out.println("Class represented by c: "
                           + c.toString());
  
        // Check if object c is compatible
        // using isAssignableFrom() method
        System.out.println("Is c compatible: "
                           + myClass.isAssignableFrom(c));
    }
}

输出:

Class represented by myClass: class Test
Class represented by c: class Test
Is c compatible: true

参考资料: https://docs.oracle.com/javase/9/docs/api/java/lang/Class.html#isAssignableFrom-java.lang.Class-