Java Class cast()用法及代碼示例

java.lang.Class類的cast()方法用於將指定的對象強製轉換為此類的對象。該方法以對象形式轉換後返回對象。

用法:

public T[] cast(Object obj)

參數：此方法接受參數obj，它是要轉換的對象

返回值：此方法以對象形式轉換後返回指定的對象。

異常：該方法拋出：

ClassCastException：如果對象不為null，並且不能分配給T類型。

下麵的程序演示了cast()方法。

範例1：

// Java program to demonstrate 
// cast() method 
  
import java.util.*; 
  
public class Test { 
  
    public static Object obj; 
  
    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()); 
  
        // Cast the object obj to object of myClass 
        // using cast() method 
        System.out.println("Object " + obj + " after cast "
                           + "upon to class Test:"
                           + myClass.cast(obj)); 
    } 
}

輸出：

Class represented by myClass:class Test
Object null after cast upon to class Test:null

範例2：

// Java program to demonstrate 
// cast() method 
  
import java.util.*; 
  
class Main { 
  
    private static int obj = 10; 
  
    public static void main(String[] args) 
        throws ClassNotFoundException 
    { 
  
        try { 
            // returns the Class object for this class 
            Class myClass = Class.forName("Main"); 
  
            System.out.println("Class represented by myClass:"
                               + myClass.toString()); 
  
            // Cast the object obj to object of myClass 
            // using cast() method 
            System.out.println("Object " + obj + " after cast "
                               + "upon to class Test:"
                               + myClass.cast(obj)); 
        } 
        catch (Exception e) { 
            System.out.println(e); 
        } 
    } 
}

輸出：

Class represented by myClass:class Main
java.lang.ClassCastException:Cannot cast java.lang.Integer to Main

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

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注：本文由純淨天空篩選整理自srinam大神的英文原創作品 Class cast() method in Java with Examples。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。