類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()方法用于檢查此Class對象所表示的類或接口是否與該類或接口相同，或者該Class對象是超類還是超接口。

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

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

  在分配對象時， isAssignableFrom()方法可能會引發異常。

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

  NullPointerException ：在異常中，當給定的類存在時為null。

Syntax:

句法：

    public boolean isAssignableFrom(Class class);

Parameter(s):

參數：

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

  類class –表示要確定的Class對象。

Return value:

返回值：

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

此方法的返回類型為boolean ，它基于以下情況返回布爾值：

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

  當類的對象可分配給該類的對象時，它返回true 。

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

  當class的對象不可分配給該Class的對象時，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

輸出量

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

翻譯自: https://www.includehelp.com/java/class-class-isassignablefrom-method-with-example.aspx