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@sureshbabu. Here is code. So that you can convert to java:

#!/usr/bin/python37
#OpenCV 4.3.0, Raspberry pi3B/+, 4b/4g/8g, Thonny 3.7.3
#Date: 2nd July, 2020

import cv2
import numpy as np
from utils import get_four_points

if __name__ == '__main__' :

    # Read in the image.
    im_src = cv2.imread("paper.jpg")
    im_src =cv2.resize(im_src, (640, 480))

    # Destination image
    size = (640,480,3)
    im_dst = np.zeros(size, np.uint8)   
    pts_dst = np.array(
                       [
                        [0,0],
                        [size[0] - 1, 0],
                        [size[0] - 1, size[1] -1],
                        [0, size[1] - 1 ]
                        ], dtype=float
                       )

    print( '''
        Click on the four corners of the book -- top left first and
        bottom left last -- and then hit ENTER''')   
    # Show image and wait for 4 clicks.
    cv2.imshow("Image", im_src)
    pts_src = get_four_points(im_src);

    # Calculate the homography
    h, status = cv2.findHomography(pts_src, pts_dst)

    # Warp source image to destination
    im_dst = cv2.warpPerspective(im_src, h, size[0:2])

    # Show output
    cv2.imshow("Image", im_dst)
    cv2.waitKey(0)

Output:

U have to rotate on editor. Becuase of paper resolution 3680x2160.