Java Field setByte()用法及代码示例

java.lang.reflect.Field的setByte()方法用于将字段的值设置为指定对象上的字节。当您需要将对象的字段值设置为字节时，可以使用此方法在对象上设置值。

用法:

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

参数：此方法接受接受两个参数：

obj：是应该修改其字段的对象，并且
b：这是要修改的obj字段的新值。

返回：此方法不返回任何内容。

异常：此方法引发以下异常：

IllegalAccessException：如果此Field对象正在强制执行Java语言访问控制，并且基础字段是不可访问的或最终的。
IllegalArgumentException：如果指定的对象不是声明基础字段(或其子类或实现者)的类或接口的实例，或者展开转换失败。
NullPointerException：如果指定的对象为null，并且该字段是实例字段。
ExceptionInInitializerError：如果此方法引发的初始化失败。

以下示例程序旨在说明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; 
}

输出：

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; 
}

输出：

Value after applying setByte is 20

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

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注：本文由纯净天空筛选整理自AmanSingh2210大神的英文原创作品 Field setByte() method in Java with Examples。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。