Java Field setByte()用法及代碼示例

java.lang.reflect.Field的setByte()方法用於將字段的值設置為指定對象上的字節。當您需要將對象的字段值設置為字節時，可以使用此方法在對象上設置值。

用法:

public void setByte(Object obj, byte b)
            throws IllegalArgumentException,
                   IllegalAccessException

參數：此方法接受接受兩個參數：

obj：是應該修改其字段的對象，並且
b：這是要修改的obj字段的新值。

返回：此方法不返回任何內容。

異常：此方法引發以下異常：

IllegalAccessException：如果此Field對象正在強製執行Java語言訪問控製，並且基礎字段是不可訪問的或最終的。
IllegalArgumentException：如果指定的對象不是聲明基礎字段(或其子類或實現者)的類或接口的實例，或者展開轉換失敗。
NullPointerException：如果指定的對象為null，並且該字段是實例字段。
ExceptionInInitializerError：如果此方法引發的初始化失敗。

以下示例程序旨在說明setByte()方法：
示例1:

// Java program to illustrate setByte() method 
  
import java.lang.reflect.Field; 
  
public class GFG { 
  
    public static void main(String[] args) 
        throws Exception 
    { 
  
        // create user object 
        Employee emp = new Employee(); 
  
        // print value of leaveLeft 
        System.out.println( 
            "Value of leaveLeft before "
            + "applying setByte is "
            + emp.leaveLeft); 
  
        // Get the marks field object 
        Field field 
            = Employee.class
                  .getField("leaveLeft"); 
  
        // Apply setByte Method 
        field.setByte(emp, (byte)2); 
  
        // print value of leaveLeft 
        System.out.println( 
            "Value of leaveLeft after "
            + "applying setByte is "
            + emp.leaveLeft); 
  
        // print value of age 
        System.out.println( 
            "Value of age before "
            + "applying setByte is "
            + emp.age); 
  
        // Get the marks field object 
        field = Employee.class.getField("age"); 
  
        // Apply setByte Method 
        field.setByte(emp, (byte)56); 
  
        // print value of age 
        System.out.println( 
            "Value of age after "
            + "applying setByte is "
            + emp.age); 
    } 
} 
  
// sample class 
class Employee { 
  
    // static byte values 
    public static byte age = 45; 
    public static byte leaveLeft = 12; 
}

輸出：

Value of leaveLeft before applying setByte is 12
Value of leaveLeft after applying setByte is 2
Value of age before applying setByte is 45
Value of age after applying setByte is 56

示例2:

// Java program to illustrate setByte() method 
  
import java.lang.reflect.Field; 
  
public class GFG { 
  
    public static void main(String[] args) 
        throws Exception 
    { 
  
        // create user object 
        User user = new User(); 
  
        // Get the id field object 
        Field field = User.class
                          .getField("id"); 
  
        // Apply setByte Method 
        field.setByte(user, (byte)20); 
  
        // print value of isActive 
        System.out.println( 
            "Value after "
            + "applying setByte is "
            + user.id); 
    } 
} 
  
// sample User class 
class User { 
  
    // static byte values 
    public static byte id = 2; 
}

輸出：

Value after applying setByte is 20

參考： https://docs.oracle.com/javase/8/docs/api/java/lang/reflect/Field.html#setByte-java.lang.Object-byte-

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注：本文由純淨天空篩選整理自AmanSingh2210大神的英文原創作品 Field setByte() 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。