Field setByte() method in Java with Examples

Last Updated : 28 Aug, 2019

setByte() method of java.lang.reflect.Field used to set the value of a field as a byte on the specified object. When you need to set the value of a field of an object as byte then you can use this method to set value over an Object.

Syntax:

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

Parameters: This method accepts accepts two parameters:

obj: which is the object whose field should be modified and
b: which is the new value for the field of obj being modified.

Return: This method returns nothing.

Exception: This method throws the following Exception:

IllegalAccessException: if this Field object is enforcing Java language access control and the underlying field is either inaccessible or final.
IllegalArgumentException: if the specified object is not an instance of the class or interface declaring the underlying field (or a subclass or implementor thereof), or if an unwrapping conversion fails.
NullPointerException: if the specified object is null and the field is an instance field.
ExceptionInInitializerError: if the initialization provoked by this method fails.

Below programs illustrate setByte() method:
Program 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;
}

Output:

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

Program 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;
}

Output:

Value after applying setByte is 20

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

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