Java Field getByte()用法及代码示例

java.lang.reflect.Field的getByte()方法用于获取必须为静态或实例字段类型的byte值。当一个类包含一个静态或实例字节字段，而我们想获取该字段的值时，则可以使用此方法返回Field的值。

用法:

public Byte getByte(Object obj)
            throws IllegalArgumentException,
                   IllegalAccessException

参数：此方法接受单个参数obj，它是要从中提取字节值的对象。

返回值：此方法返回转换为字节类型的字段的值。

异常：此方法引发以下异常：

IllegalAccessException：如果Field对象正在强制执行Java语言访问控制并且基础字段不可访问，则抛出此异常。
IllegalArgumentException：如果指定的对象不是声明基础字段的类或接口的实例，或者无法通过扩展转换将字段值转换为类型字节，则抛出此异常。
NullPointerException ：如果指定对象为null并且该字段是实例字段，则抛出此异常。
ExceptionInInitializerError：如果此方法引发的初始化失败，则抛出此异常。

以下示例程序旨在说明getByte()方法：
示例1:

// Java program to demonstrate the getByte() method 
  
import java.lang.reflect.Field; 
  
public class GFG { 
  
    public static void main(String[] args) 
        throws NoSuchFieldException, 
               SecurityException, 
               IllegalArgumentException, 
               IllegalAccessException 
    { 
  
        // Create the User class object 
        User user = new User(); 
  
        // Get the identificationByte field object 
        Field field 
            = User.class
                  .getField("identificationByte"); 
  
        // Apply getByte Method on User Object 
        // to get the value of identificationByte field 
        byte value = field.getByte(user); 
  
        // print result 
        System.out.println("Value of Byte Field"
                           + " identificationByte is "
                           + value); 
  
        // Now Get the selectionByte field object 
        field = User.class.getField("selectionByte"); 
  
        // Apply getByte Method on User Object 
        // to get the value of selectionByte field 
        value = field.getByte(user); 
  
        // print result 
        System.out.println("Value of Byte Field"
                           + " selectionByte is "
                           + value); 
    } 
} 
  
// sample User class 
class User { 
  
    // static Byte values 
    public static byte identificationByte = 'E'; 
    public static byte selectionByte = 121; 
  
    // getter and setter methods 
    public static byte getIdentificationByte() 
    { 
        return identificationByte; 
    } 
  
    public static void
    setIdentificationByte(byte identificationByte) 
    { 
        User.identificationByte = identificationByte; 
    } 
  
    public static byte getSelectionByte() 
    { 
        return selectionByte; 
    } 
    public static void
    setSelectionByte(byte selectionByte) 
    { 
        User.selectionByte = selectionByte; 
    } 
}

输出：

Value of Byte Field identificationByte is 69
Value of Byte Field selectionByte is 121

示例2:

// Java program to demonstrate the getByte() method 
  
import java.lang.reflect.Field; 
  
import java.lang.reflect.Field; 
  
public class GFG { 
  
    public static void main(String[] args) 
        throws NoSuchFieldException, 
               SecurityException, 
               IllegalArgumentException, 
               IllegalAccessException 
    { 
  
        // Create the Codes class object 
        Codes codes = new Codes(); 
  
        // Get the value field object 
        Field field 
            = Codes.class.getField("value"); 
  
        // Apply getByte Method on field Object 
        // to get the value of value field 
        byte value = field.getByte(codes); 
  
        // print result 
        System.out.println("Value: " + value); 
    } 
} 
// Codes class 
class Codes { 
    // Byte field 
    public static byte value = 12; 
}

输出：

Value: 12

参考文献： https://docs.oracle.com/javase/8/docs/api/java/lang/reflect/Field.html#getByte-java.lang.Object-

相关用法

注：本文由纯净天空筛选整理自AmanSingh2210大神的英文原创作品 Field getByte() 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。