How to Create a custom widget for wordpress sidebar

How to create a custom widget for your theme or custom plugin , just copy and paste below code and paste it into your theme's functions.php or your custom plugin file

class showtable_widget extends WP_Widget {

function __construct() {
    global $wpdb;
parent::__construct(

'showtable_widget',   // custom widget slug put slug whatever you like

__('Show xml feed table', 'showtable_widget'),   // widget title display in admin side widget area

array( 'description' => __( 'Display feed table in sidebar ', 'showtable_widget' ), )  // description for
);    // your widget purpose
}

public function widget( $args, $instance ) {   // this function use for display data frontend side
     global $wpdb;
$title = apply_filters( 'widget_title', $instance['title'] );

echo $args['before_widget'];
if ( ! empty( $title ) )
echo $args['before_title'] . $title . $args['after_title'];


// custom code started for display in frontside

echo __( 'Hello, World! Have a great day', 'showtable_widget' );

// custom code end for display in frontside
echo $args['after_widget'];
}


public function form( $instance ) {  // this form display in admin side for change title
if ( isset( $instance[ 'title' ] ) ) {
$title = $instance[ 'title' ];
}
else {
$title = __( 'Show Table', 'showtable_widget' );
}
if(isset($instance['noofrow']))
{
    $noofrow = $instance['noofrow'];
}else
{
    $noofrow = 5;
}
?>
<p>
<label for="<?php echo $this->get_field_id( 'title' ); ?>"><?php _e( 'Title:' ); ?></label>
<input class="widefat" id="<?php echo $this->get_field_id( 'title' ); ?>" name="<?php echo $this->get_field_name( 'title' ); ?>" type="text" value="<?php echo esc_attr( $title ); ?>" />
</p><p>
<label for="<?php echo $this->get_field_id( 'noofrow' ); ?>"><?php _e( 'No of Rows:' ); ?></label>
<input class="widefat" id="<?php echo $this->get_field_id( 'noofrow' ); ?>" name="<?php echo $this->get_field_name( 'noofrow' ); ?>" type="text" value="<?php echo esc_attr( $noofrow ); ?>" />
</p>
<?php
}


public function update( $new_instance, $old_instance ) {
$instance = array();
$instance['title'] = ( ! empty( $new_instance['title'] ) ) ? strip_tags( $new_instance['title'] ) : '';
$instance['noofrow'] = ( ! empty( $new_instance['noofrow'] ) ) ? strip_tags( $new_instance['noofrow'] ) : '';
return $instance;
}
}
function rj_load_widget() {  // load widget
register_widget( 'showtable_widget' );
}
add_action( 'widgets_init', 'rj_load_widget' );     // display widget action