Java应用技巧

    技术2022-05-11  57

    ---- 1. Applet 与 Application 合 并 ---- Java 是 一 种 建 立 分 布 应 用 程 序 的 技 术 。 它 是 网 络 编 程 的 最 优 秀 工 具 。 使 Internet 的 应 用 从 通 讯 工 具 扩 展 到 能 够 运 行 成 熟 应 用 程 序 的 网 络 。 ---- Java 程 序 有 两 种 类 型:Applet 和 Application 。 简 单 的 讲 ,Applet 就 是 嵌 入Web 文 档 的 程 序 , 而Application 则 是 所 有 其 它 类 型 的 程 序 。 ---- 就Java 而 言 ,Applet 与 Application 的 大 小 和 复 杂 性 都 没 有 限 制 , 但 是 因 为Applet 主 要 是 用 于 网 络 通 讯 , 由 于 通 讯 速 度 有 限 , 下 载 时 间 较 长 , 因 而 Applet 一 般 来 说 规 模 较 小 , 而 对 于Application 则 无 此 顾 虑 。 ---- Applet 与 Application 之 间 的 技 术 差 别 来 源 于 其 运 行 环 境 的 差 别 。 Applet 需 要 来 自 浏 览 器 的 大 量 信 息: 浏 览 器 客 户 机 的 位 置 和 大 小 、 嵌 入 主HTML 文 档 的 参 数 、 初 始 化 过 程(init) 、 启 动 过 程(start) 、 停 止 过 程(stop) 、 终 止 过 程(destory) 、 绘 图 过 程(paint) 等 等 , 而Application 则 相 对 要 简 单 得 多 , 它 来 自 外 部 世 界 的 唯 一 输 入 就 是 命 令 行 参 数 。 ---- 对 于 Applet 必 须 做 为java.applet.Applet 的 子 类 , 而Application 则 必 须 有 一 个 公 共 的 方 法 main( ) 。 其 次 , 两 者 的 主 线 程 是 不 同 的 ,Applet 是 由 方 法 init( ) 来 对applet 进 行 初 始 化 的 , 而Application 则 由 方 法main( ) 来 开 始 运 行 程 序 的 。 一 般 地 ,Java 的 Applet 和 Application 是 完 全 遵 照 以 上 的 原 则 进 行 编 程 的 , 但 是 , 我 们 可 以 运 用 技 巧 写 出 即 是Applet 又 是 Application 的 程 序 来 。 这 样 , 即 可 以 使 我 们 更 进 一 步 了 解Java 的 内 部 结 构 又 可 以 使 同 一 程 序 运 行 于 不 同 的 运 行 环 境 、 还 可 以 提 高 研 究Java 的 兴 趣 。 ---- 例 程 如 下:       import java.applet.*;      import java.awt.*;      import java.awt.event.*;             public class Example extends Applet implements                        ActionListener{ // #1         public static void main(String[] args){           Frame win=new Frame("Example");           Example example=new Example();           win.add(揅enter", example);           example.init();             // #2           win.setSize(600,360);           win.setVisible(true);         }      public void init(){  // #3           Button button;           Label  label;           button=new Button(" OK "):           button.setBounds(280,200,100,20);           button.addActionListener(this);           label=new Label();           label.setBounds(260,100,200,20);           add(button);           add(label);         }       public void actionPerformed(ActionEvent e){           Object source=e.getSource();           if(source==button){             label.setText(" It is a example !");           }         }      }---- 在 程 序 中 的 #1 处 , 必 须 让 程 序 继 承java.applet.Applet 类 这 是 做 为Applet 的 必 要 条 件 , 在 #2 处 , 需 要 生 成 本 类 的 一 个 实 例 example , 通 过 此 实 例 来 调 用init() 方 法 , #3 是 init() 方 法 。 ---- 如 果 把 该 程 序 看 作Applet , 它 只 是 覆 盖 了init() 方 法 和actionPerformed( ) 方 法 来 响 应Button 事 件 。 如 果 作 为Application , 则 由main( ) 方 法 开 始 , 先 生 成 程 序 本 身 的 实 例 将 程 序 加 入 窗 口 , 然 后 调 用init() 方 法 。 编 译 此 程 序 , 即 可 以 在 提 示 下 作 为Application 直 接 运 行 , 又 可 以 作 为Applet 送 入 任 何 浏 览 器 。 ---- 2. Java 中 的 发 声 提 示 ---- Java 作 为 一 种 网 络 编 程 语 言 , 在 浏 览 器 中 即 可 以 进 行 动 画 演 示 , 也 可 以 播 放 声 音 。 在 人 机 的 交 互 过 程 中 , 为 了 加 强 效 果 或 起 到 提 示 的 作 用 , 需 要 加 入 声 音 。 ---- Java 的 包 java.applet 中 有AudioClip 接 口 , 此 接 口 封 装 有 关 声 音 片 断 的 一 些 常 用 方 法 。 用 法 如 下:        AudioClip audio;         audio=getAudioClip(getCodeBase(),"Hi.au");         audio.play();---- 第 一 行 生 成 接 口AudioClip 的 一 个 变 量 , 第 二 行 利 用 此 变 量 取 得 声 音 文 件 Hi.au , 此 文 件 与 程 序 本 身 在 同 一 目 录 下,getCodeBase() 方 法 是 用 来 取 得Applet 的class 文 件 的URL 地 址 。 第 三 行 是 播 放 声 音 文 件 。 在Applet 中 利 用 此 用 法 可 在 浏 览 器 中 发 出 声 音 。 那 么 , 在Application 中 是 否 也 可 以 用 此 方 法 来 发 出 声 音 呢 ? 不 可 以 。 因 为 接 口AudioClip 是 在 包 java.applet 中 , 而 此 包 只 适 用 于Applet 。 是 否 可 以 用 其 它 方 法 来 实 现 呢 ? 我 们 可 以 利 用 1 中 的 技 巧 来 编 写 一 个 即 是Applet 又 是 Application 的 程 序 试 试 。 结 果 , 还 是 不 行 。 这 是 因 为play() 方 法 只 能 在Applet 中 实 现 , 对 于Applicationplay() 方 法 是 不 能 够 被 调 用 的 。 ---- 那 么 , 如 何 在Application 中 实 现 发 声 提 示 呢 ? ---- 记 得 VB 中 有 beep 语 句 来 使 系 统 发 声 器(System Speaker ) 发 声 , 那 么 ,Java 中 也 应 有 类 似 的 方 法 。 ---- 在 Java 的 java.awt.Toolkit 类 中 有 方 法beep() 是 来 实 现 这 一 功 能 的 。 类 Toolkit 是 抽 象 类 , 它 是 实 现AWT 的 所 有 工 具 的 父 类 。 Java 中 的 抽 象 类 是 不 能 够 实 例 化 的 , 但 是 一 般 地 , 抽 象 类 可 以 生 成 变 量 , 然 后 利 用 抽 象 类 中 的 某 一 方 法 来 取 得 此 类 的 替 代 品 。 在 Toolkit 中 是 利 用 getDefaultToolkit() 方 法 来 实 现 的 。 现 在 给 出 一 个 实 例: 这 是 一 个 客 户 机/ 服 务 器 的Application 。 当 服 务 器 运 行 时 如 果 有 客 户 机 与 服 务 器 相 连 , 则 服 务 器 会 自 动 发 声 警 报 提 示 服 务 器 端 的 用 户 有 客 户 要 与 自 己 进 行 对 话 。 ---- 程 序 如 下:  服 务 器:import java.util.*;import java.io.*;import java.net.*;import java.awt.*;public class ServerT{  public static void main(String[] args){    Server server;    String clientRequest;    boolean quit=false;    server=new Server(8001);    while(!quit){      DataInputStream keyboard=new DataInputStream(System.in);      try{        clientRequest=server.in.readLine();        if(clientRequest.trim().equals("CLOSE")){          System.out.println("Client says: "+clientRequest);          System.exit(1);        }        System.out.println("Client says: "+clientRequest);        server.out.println(keyboard.readLine());       }catch(IOException e){        System.out.println("IOException in server.in.readLine()"+e);        System.exit(1);      }    }  }}class Server{  private ServerSocket server;  private Socket socket;  public DataInputStream in;  public PrintStream out;  public Server(int port){    try{      server=new ServerSocket(port);      System.out.println("/n*************************************************");      System.out.println("/n @(#)Net Applecation               Version 1.00 97/12/30 ");      System.out.println(" Copyright (c) 1997              (Lui DongBing) All Rights Reserved.");      System.out.println("/n ***************************************************");      System.out.println("/n Server is: /n "+server);      socket=server.accept();      for(int i=0;I < 260;i++){ // 发 声 提 示Toolkit.getDefaultToolkit().beep();}System.out.println("/n Server is ready ! /n");in=new DataInputStream(socket.getInputStream());out=new PrintStream(socket.getOutputStream());out.println("We connect in "+new Date());}catch(IOException e){System.out.println("Server is failied !");}}} 客 户 机 :import java.util.*;import java.io.*;import java.net.*;public class ClientT{public static void main(String[] args){String welcome,response;Client client;client=new Client("100.100.100.1",8001); // #1DataInputStream keyboard=new DataInputStream(System.in);boolean Bye=false;while(!Bye){try{welcome=client.in.readLine();System.out.println(" Server says: "+welcome);client.out.println(keyboard.readLine());}catch(IOException e){System.out.println("/n The talk is CLOSED !");System.exit(1);}}try{Thread.sleep(200);}catch(Exception e){System.out.println("It is a bug !");}}}class Client{public DataInputStream in;public PrintStream out;private Socket client;public Client(String host,int port){try{client=new Socket(host,port);System.out.println("/n ***************************************************");System.out.println("/n @(#)Net Applecation Version 1.00 97/12/30 ");System.out.println(" Copyright (c) 1997 (Lui DongBing) All Rights Reserved.");System.out.println("/n **************************************************");System.out.println("/n Client socket:"+client);System.out.println("/n Client is ready ! /n");out=new PrintStream(client.getOutputStream());in=new DataInputStream(client.getInputStream());}catch(IOException e){System.out.println("/n IOException !/n"+e);System.exit(1);}}}

     

    100.100.100.1为本机地址


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