标签：sys str 通过 htm trace generated dir cep imp
builer英文名原意为建造者，在Builder模式中，主要有Builer（建造者），concreteBuilder(具体的建造者），Directer（监工）以及Client（使用者），其中Builder定义了各种建造的方法，并作为Directer的字段，并在Directer中定义了builder的方法执行顺序以及执行时所需要的参数，ConcrereBuilder则实现了Builder中的方法，下面通过案例说明：
用Builder模式编写文档，文档中含有一个标题，含有几个字符串，含有条目项目。
首先定义Builder
1 package framework; 2 3 public interface Builder { 4 public abstract void makeTitle(String title); 5 6 public abstract void makeString(String str); 7 8 public abstract void makeItems(String[] items); 9 10 public abstract void close(); 11 }
然后是Directer类
1 package framework; 2 3 public class Director { 4 private Builder builder; 5 6 public Director(Builder builder) { 7 this.builder = builder; 8 } 9 10 public void construct() { 11 builder.makeTitle("Greeting"); 12 builder.makeString("从早上到下午"); 13 builder.makeItems(new String[] { "早上好", "下午好", }); 14 builder.makeString("晚上"); 15 builder.makeItems(new String[] { "晚上好", "晚安", "再见", }); 16 builder.close(); 17 } 18 }
然后是实现了Builder的两个子类，这两个子类充当concreteBUilder角色
package concrete; import framework.Builder; public class HTMLBuilder implements Builder { private StringBuffer buffer = new StringBuffer(); @Override public void makeTitle(String title) { buffer.append("========================================\n"); buffer.append("[" + title + "]\n"); buffer.append("\n"); } @Override public void makeString(String str) { buffer.append("@" + str + ":\n"); buffer.append("\n"); } @Override public void makeItems(String[] items) { int length = items.length; for (int i = 0; i < length; i++) { buffer.append(" ." + items[i] + "\n"); } buffer.append("\n"); } @Override public void close() { buffer.append("===========================================\n"); } public String getResult() { return buffer.toString(); } }
1 package concrete; 2 3 import java.io.FileWriter; 4 import java.io.IOException; 5 import java.io.PrintWriter; 6 7 import framework.Builder; 8 9 public class TextBuilder implements Builder { 10 private String filename; 11 12 private PrintWriter writer; 13 14 @Override 15 public void makeTitle(String title) { 16 filename = title + ".html"; 17 try { 18 writer = new PrintWriter(new FileWriter(filename)); 19 } catch (IOException e) { 20 21 // Auto-generated catch block 22 e.printStackTrace(); 23 24 } 25 writer.println("<html><head><title>" + title + "</title></head><body>"); 26 writer.println("<h1>" + title + "</h1>"); 27 } 28 29 @Override 30 public void makeString(String str) { 31 writer.println("<p>" + str + "</p>"); 32 } 33 34 @Override 35 public void makeItems(String[] items) { 36 writer.println("<ul>"); 37 for (int i = 0; i < items.length; i++) { 38 writer.println("<li>" + items[i] + "</li>"); 39 } 40 writer.println("</ul>"); 41 } 42 43 @Override 44 public void close() { 45 writer.println("</body></html>"); 46 writer.close(); 47 48 } 49 50 public String getResult() { 51 return filename; 52 } 53 }
最后是Main程序入口，充当Client角色
1 public class Main { 2 3 public static void main(String[] args) { 4 if (args.length != 1) { 5 System.out.println("哈哈哈哈"); 6 System.exit(0); 7 } 8 if (args[0].equals("plain")) { 9 TextBuilder textBuilder = new TextBuilder(); 10 Director director = new Director(textBuilder); 11 director.construct(); 12 String result = textBuilder.getResult(); 13 System.out.println(result); 14 } else if (args[0].equals("html")) { 15 HTMLBuilder htmlBuilder = new HTMLBuilder(); 16 Director director = new Director(htmlBuilder); 17 director.construct(); 18 String result = htmlBuilder.getResult(); 19 System.out.println(result + "文件编写完成"); 20 } else { 21 System.exit(0); 22 ; 23 } 24 } 25 26 }
当我们需要编写其他类型的文档时并且文档内容不变时，并不需要对Directer和Builder修改，仅仅定义一个子类继承Builder就可以了，这里的Directer与Builder就可以作为组件重复使用，这就是Builder模式的优点。
标签：sys str 通过 htm trace generated dir cep imp
原文地址：https://www.cnblogs.com/xiaoyaomianbiren/p/12182642.html
