Java Class isInstance()用法及代碼示例

java.lang.Class類的isInstance()方法用於檢查指定的對象是否兼容分配給該Class的實例。如果指定對象為非null，並且可以強製轉換為此類的實例，則該方法返回true。否則返回false。

用法:

public boolean isInstance(Object object)

參數：此方法接受object作為參數，這是要檢查與此Class實例的兼容性的指定對象。

返回值：如果指定對象為非null，並且可以強製轉換為此類的實例，則此方法返回true。否則返回false。

下麵的程序演示了isInstance()方法。

示例1:

// Java program to demonstrate isInstance() 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 isInstance() method 
        System.out.println("Is c compatible: "
                           + myClass.isInstance(c)); 
    } 
}

輸出：

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

示例2:

// Java program to demonstrate isInstance() 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 isInstance() method 
        System.out.println("Is c compatible: "
                           + myClass.isInstance(c)); 
    } 
}

輸出：

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

參考： https://docs.oracle.com/javase/9/docs/api/java/lang/Class.html#isInstance-java.lang.Object-

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