Question

Hello. I'm trying to write down java code making stars whose numbers are determined by user input on the console (each star's data are stored in ArrayList).

the class extends JFrame and its color, size(Zoom in and Zoom out), and location are changing every time.

Moreover, its angular rotation is changed at a certain determined degree.

Does anyone know how to write down the java code of this question?

Answer 1

Solution:

stars_frame.java:

//stars_frame.java file to draw number of stars as input given by user

import java.awt.Color;

import java.util.Scanner;

import javax.swing.JFrame;

import java.util.ArrayList;

import java.util.Random;

public class stars_frame extends JFrame {

// size of window

private final int WINDOW_SIZE = 600;

// array list of stars_frame

private ArrayList<Star> stars_frameList;

//n is numbers of starts given as input

public stars_frame(int n) {

// passing a title to super class constructor

super("stars_frame");

Random random = new Random();

// no layout manager for absolute positioning

setLayout(null);

// initializing array list

stars_frameList = new ArrayList<Star>();

// looping for number of times to draw stars_frame

for (int i = 0; i < n; i++) {

// generating a random size between 50 and 150

int size = random.nextInt(100) + 50;

// creating a star with random angle, random color and above size

Star star = new Star(random.nextInt(360), new Color(

random.nextInt(256), random.nextInt(256),

random.nextInt(256)), size);

// specifying star in a random location on the window

star.setBounds(random.nextInt(WINDOW_SIZE - size),

random.nextInt(WINDOW_SIZE - size), size, size);

// adding stars_frame to window

add(star);

// adding to list, so that each star can be altered later when you want

stars_frameList.add(star);

}

//display window

setDefaultCloseOperation(EXIT_ON_CLOSE);

setSize(WINDOW_SIZE, WINDOW_SIZE);

setVisible(true);

}

public static void main(String[] args) {

//taking input as number of stars_frame

Scanner scanner = new Scanner(System.in);

System.out.print("Enter number of stars_frame: ");

int no_stars = scanner.nextInt();

new stars_frame(no_stars);

}

}

Star.java:

//Star.java extending JPanel to represent a single star

import java.awt.Color;//color package

import java.awt.Dimension;//for dimensions

import java.awt.Graphics;//graphics package

import java.awt.Polygon;

import javax.swing.JPanel;

public class Star extends JPanel {

// attributes using to store angle and color

private double angle;

private Color color;

// constructor to take angle, color and size

public Star(double angle, Color color, int size) {

this.angle = angle;

this.color = color;

// trnsperant background color

setBackground(new Color(0, 0, 0, 0));

setPreferredSize(new Dimension(size, size));

}

@Override

protected void paintComponent(Graphics g) {

super.paintComponent(g);

// angle

double temp_angle = angle;

// center-coordinates

double Center_X = getWidth() / 2, Center_Y = getHeight() / 2;

// distance between edge and center of the star

double radius = getWidth() / 2;

// distance between center of star to the vertex between edges

double innerRadius = getWidth() / 5;

// dividing a circle into 10 parts

int angle_difference = 360 / 10;

// polygan

Polygon polygon = new Polygon();

double x, y;

// looping for 10 times

for (int i = 0; i < 10; i++) {

if (i % 2 == 0) {

x = Center_X + radius * Math.cos(Math.toRadians(temp_angle));

y = Center_Y + radius * Math.sin(Math.toRadians(temp_angle));

} else {

x = Center_X + innerRadius

* Math.cos(Math.toRadians(temp_angle));

y = Center_Y + innerRadius

* Math.sin(Math.toRadians(temp_angle));

}

// adding to polygon

polygon.addPoint((int) x, (int) y);

// updating temp_angle

temp_angle += angle_difference;

}

// white colour to fill polygon

g.setColor(color);

g.fillPolygon(polygon);

// black colour for polygan outline

g.setColor(Color.BLACK);

g.drawPolygon(polygon);

}

}

Example input of n=20:

Thank you, Have a great day:-)