类class isAssignableFrom()方法 (Class class isAssignableFrom() method)

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

  isAssignableFrom()方法在java.lang包中可用。

• isAssignableFrom() method is used to check whether the class or an interface denoted by this Class object is either the same as, or the Class object is a superclass or superinterface.

  isAssignableFrom()方法用于检查此Class对象所表示的类或接口是否与该类或接口相同，或者该Class对象是超类还是超接口。

• isAssignableFrom() 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.

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

• isAssignableFrom() method may throw an exception at the time of assigning an object.

  在分配对象时， isAssignableFrom()方法可能会引发异常。

  NullPointerException: In the exception, when the given class exists null.

  NullPointerException ：在异常中，当给定的类存在时为null。

Syntax:

句法：

    public boolean isAssignableFrom(Class class);

Parameter(s):

参数：

• Class class – represents the Class object to be determined.

  类class –表示要确定的Class对象。

Return value:

返回值：

The return type of this method is boolean, it returns a boolean value based on the following cases,

此方法的返回类型为boolean ，它基于以下情况返回布尔值：

• It returns true, when the object of class is assignable to object of this Class.

  当类的对象可分配给该类的对象时，它返回true 。

• It returns false, when the object of class is not assignable to object of this Class.

  当class的对象不可分配给该Class的对象时，它返回false 。

Example:

例：

// Java program to demonstrate the example 
// of boolean isAssignableFrom(Class class) method of Class 
public class Parent {
public static void main(String[] args) throws Exception {
// Create and Return Parent Class object
Parent p = new Parent();
Class cl1 = p.getClass();
// Create and Return Child Class object
Child ch = new Child();
Class cl2 = ch.getClass();
// We are checking the given Parent class is 
// Assignable from Child Class
boolean child = cl2.isAssignableFrom(cl1);
System.out.println("Is" + " " + cl1.getSimpleName() + " " + "Assignable from Child: " + " " + child);
// We are checking the given Child class is 
// Assignable from Parent Class
boolean parent = cl1.isAssignableFrom(cl2);
System.out.println("Is" + " " + cl2.getSimpleName() + " " + "Assignable from Parent: " + " " + parent);
}
}
class Child extends Parent {
public Child() {
// Default Constructor with blank implementation
}
}

Output

输出量

Is Parent Assignable from Child:  false
Is Child Assignable from Parent:  true

翻译自: https://www.includehelp.com/java/class-class-isassignablefrom-method-with-example.aspx