cityinthunder.java

Java案例开发集锦,里面提供了很好的学习例子

import java.applet.Applet;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;

//在applet中支持线程，需要实现Runnable接口
public class CityInThunder extends Applet implements Runnable
{
	private Thread thread = null; //applet支持的线程

	private boolean no_thunder = true; //没有闪电的标志变量

	private boolean thunder = true; //有闪电的标志变量

	private int[] light;

	private int[] b1;

	private int[] b2;

	private Color whiteSky = new Color(0, 0, 65), yellowSky = new Color(144,
			40, 40);//白色闪电、黄色闪电

	private Image buffer, image;

	private String delay = "3";

	public void init() {
		//初始化applet
		String imageName = getParameter("Image1");
		image = getImage(getCodeBase(), imageName);
		light = new int[getSize().height];
		b1 = new int[getSize().height];
		b2 = new int[getSize().height];
		buffer = this.createImage(getSize().width, getSize().height);
	}

	public void paint(Graphics g) {
		int i, thr;
		if (no_thunder) //没有闪电
		{
			g.setColor(Color.black); //设背景色为黑色
			g.fillRect(0, 0, getSize().width, getSize().height); //填充背景色
			g.drawImage(image, 0, 0, this); //输出City.gif
		} else //有闪电
		{
			if (thunder) //白色闪电
				g.setColor(whiteSky); //设背景色为白色
			else
				//黄色闪电
				g.setColor(yellowSky); //设背景色为黄色
			g.fillRect(0, 0, getSize().width, getSize().height); //填充背景色
			//输出闪电图像
			thr = (int) (0.8F * getSize().height);
			for (i = 1; i < getSize().height; i++) {
				if (i < thr) { //输出闪电周围的灰色矩形
					g.setColor(Color.darkGray);
					g.drawRect(light[i] - 4, i, 3, 1);
					g.drawRect(light[i] + 2, i, 3, 1);
					g.setColor(Color.gray);
					g.drawRect(light[i] - 1, i, 1, 1);
					g.drawRect(light[i] + 1, i, 1, 1);
				}
				if (thunder) { //白色闪电
					g.setColor(Color.white);
				} else
					//黄色闪电
					g.setColor(Color.yellow);
				g.drawLine(light[i], i, light[i - 1], i - 1);
				if (b1[i] >= 0) { //输出闪电折线
					g.drawLine(b1[i], i, b1[i - 1], i - 1);
				}
				if (b2[i] >= 0) { //输出闪电折线
					g.drawLine(b2[i], i, b2[i - 1], i - 1);
				}
			}
			//输出城市图像city.gif
			g.drawImage(image, 0, 0, this);
			thunder = !thunder;
		}
	}

	void drawBuffer() {
		//调用paint()方法
		Graphics g;
		g = buffer.getGraphics();
		paint(g);
	}

	public void start() {
		//启动applet，创建并启动线程
		if (thread == null) {
			thread = new Thread(this);
			thread.start();
		}
	}

	public void stop() {
		if (thread != null) {
			thread.stop();
			thread = null;
		}
	}

	void createThunder() {
		//生成闪电的坐标数组数据
		int i;
		int bs1, bs2; //开始位置的坐标
		int be1, be2; //结束位置的坐标
		light[0] = (int) (Math.random() * getSize().width); //随机产生闪电出现的位置
		b1[0] = light[0];
		b2[0] = light[0];
		bs1 = (int) (Math.random() * getSize().height) + 1;
		bs2 = (int) (Math.random() * getSize().height) + 1;
		be1 = bs1 + (int) (0.5 * Math.random() * getSize().height) + 1;
		be2 = bs2 + (int) (0.5 * Math.random() * getSize().height) + 1;
		for (i = 1; i < getSize().height; i++) {
			light[i] = light[i - 1] + ((Math.random() > 0.5) ? 1 : -1);
			b1[i] = light[i];
			b2[i] = light[i];
		}
		for (i = bs1; i < getSize().height; i++) {
			b1[i] = b1[i - 1] + ((Math.random() > 0.5) ? 2 : -2);
		}
		for (i = bs2; i < getSize().height; i++) {
			b2[i] = b2[i - 1] + ((Math.random() > 0.5) ? 2 : -2);
		}
		for (i = be1; i < getSize().height; i++) {
			b1[i] = -1;
		}
		for (i = be2; i < getSize().height; i++) {
			b2[i] = -1;
		}
	}

	public void run() {
		//启动进程

		Graphics g;
		while (true) {
			try {
				//输出图像
				drawBuffer();
				g = this.getGraphics();
				g.drawImage(buffer, 0, 0, this);
				//线程休眠，时间随机产生
				Thread.sleep((int) (Integer.parseInt(delay) * 1000 * Math
						.random()));
				//无闪电标记变量置位
				no_thunder = false;
				//创建闪电
				createThunder();
				//输出图像
				drawBuffer();
				g = this.getGraphics();
				g.drawImage(buffer, 0, 0, this);
				//线程休眠1秒
				Thread.sleep(1000);
				//无闪电标记变量置位
				no_thunder = true;
			} catch (InterruptedException e) {
				stop();//发生异常，停止线程
			}
		}
	}
}