Field setBoolean() method in Java with Examples

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

public void setBoolean(Object obj, boolean z)
            throws IllegalArgumentException,
                   IllegalAccessException

Parameters: This method accepts two parameters:

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

Return value: This method returns nothing. Exception: This method throws 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 implementer 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 setBoolean() method: Program 1:

Java

// Java program to illustrate setBoolean() method

import java.lang.reflect.Field;

public class GFG {

    public static void main(String[] args)
        throws Exception
    {

        // create user object
        User user = new User();

        // print value of isActive
        System.out.println("Value before "
                           + "applying setBoolean is "
                           + user.isActive);

        // Get the marks field object
        Field field
            = User.class
                  .getField("isActive");

        // Apply setBoolean Method
        field.setBoolean(field, false);

        // print result
        System.out.println("Value after "
                           + "applying setBoolean is "
                           + user.isActive);
    }
}

// sample User class
class User {

    // static boolean values
    public static boolean isActive = true;
}

Output:

Value before applying setBoolean is true
Value after applying setBoolean is false

Program 2:

Java

// Java program to illustrate setBoolean() 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 isManager
        System.out.println("Value of isManager before "
                           + "applying setBoolean is "
                           + emp.isManager);

        // Get the marks field object
        Field field
            = Employee.class
                  .getField("isManager");

        // Apply setBoolean Method
        field.setBoolean(emp, false);

        // print value of isActive
        System.out.println("Value of isPresent before "
                           + "applying setBoolean is "
                           + emp.isManager);

        // print value of isManager
        System.out.println("Value of isManager before "
                           + "applying setBoolean is "
                           + emp.isPresent);

        // Get the marks field object
        field = Employee.class
                    .getField("isPresent");

        // Apply setBoolean Method
        field.setBoolean(emp, true);

        // print value of isActive
        System.out.println("Value of isPresent before "
                           + "applying setBoolean is "
                           + emp.isPresent);
    }
}

// sample User class
class Employee {

    // static boolean values
    public static boolean isPresent = false;
    public static boolean isManager = true;
}

Output:

Value of isManager before applying setBoolean is true
Value of isPresent before applying setBoolean is false
Value of isManager before applying setBoolean is false
Value of isPresent before applying setBoolean is true

References: https://docs.oracle.com/javase/8/docs/api/java/lang/reflect/Field.html#setBoolean-java.lang.Object-boolean-