Field setByte() method in Java with Examples - GeeksforGeeks

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:
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 classclass Employee {      // static byte values    public static byte age = 45;    public static byte leaveLeft = 12;}
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 classclass User {      // static byte values    public static byte id = 2;}
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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