作用：
組裝具有復(fù)雜結(jié)構(gòu)的實例，組裝的過程被隱藏在Director角色中
理解：
當(dāng)創(chuàng)建的對象特別的復(fù)雜，把這個復(fù)雜的對象進行拆分。這個復(fù)雜對象的各個部分經(jīng)常會需要面臨劇烈的變化，但是他們的組合在一起的算法是相對穩(wěn)定
的。Builder模式就是一種“封裝機制”來隔離“復(fù)雜對象的各個部分”的變化，從而保持系統(tǒng)中的“穩(wěn)定構(gòu)建算法”不隨需求發(fā)生改變而改變。
Builder模式.png
小案例
Builder.java
package example1;
/**
* @Author:DarknessShadow
* @description:
* @date 2020/5/13 10:19
*/
public abstract class Builder {
public abstract void makeTitle(String title);
public abstract void makeString(String string);
public abstract void makeItems(String[] items);
public abstract void close();
}
HtmlBuilder.java
package example1;
import java.io.FileWriter;
import java.io.PrintWriter;
/**
* @Author:DarknessShadow
* @description:
* @date 2020/5/13 10:41
*/
public class HTMLBuilder extends Builder {
private String filename;
private PrintWriter writer;
@Override
public void makeTitle(String title) {
filename = title + ".html";
try {
writer = new PrintWriter(new FileWriter(filename));
} catch (Exception e) {
e.printStackTrace();
}
writer.println("<html><head><title>" + title + "</title></head><body>");
writer.println("<h1>" + title + "</h1>");
}
@Override
public void makeString(String string) {
writer.println("<p>" + string + "</p>");
}
@Override
public void makeItems(String[] items) {
writer.print("<ul>");
for (int i = 0; i < items.length; i++) {
writer.println("<li>" + items[i] + "</li>");
}
writer.println("</ul");
}
@Override
public void close() {
writer.println("</body></html>");
writer.close();
}
public String getResult() {
return filename;
}
}
TextBuilder.java
package example1;
/**
* @Author:DarknessShadow
* @description:
* @date 2020/5/13 10:25
*/
public class TextBuilder extends 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 string) {
buffer.append("@" + string + "\n");
buffer.append("\n");
}
@Override
public void makeItems(String[] items) {
for (int i = 0; i < items.length; i++) {
buffer.append(" ." + items[i] + "\n");
}
buffer.append("\n");
}
@Override
public void close() {
buffer.append("==============================\n");
}
public String getResult() {
return buffer.toString();
}
}
Director.java
package example1;
/**
* @Author:DarknessShadow
* @description:
* @date 2020/5/13 10:20
*/
public class Director {
private Builder builder;
public Director(Builder builder) {
this.builder = builder;
}
public void construct() {// 編寫文檔
builder.makeTitle("Greeting"); // 標題
builder.makeString("從早上到下午"); // 字符串
builder.makeItems(new String[]{ // 條目
"good morning",
"good afternoon",
});
builder.makeString("晚上");
builder.makeItems(new String[]{ // 條目
"good night",
"good bye",
});
builder.close();
}
}
Main.java
package example1;
/**
* @Author:DarknessShadow
* @description:
* @date 2020/5/13 10:47
*/
public class Main {
public static void main(String[] args) {
String arg = "plain";
if ("plain".equals(arg)) {
TextBuilder textBuilder = new TextBuilder();
Director director = new Director(textBuilder);
director.construct();
String result = textBuilder.getResult();
System.out.println(result);
} else if ("html".equals(arg)) {
HTMLBuilder htmlBuilder = new HTMLBuilder();
Director director = new Director(htmlBuilder);
director.construct();
String filename = htmlBuilder.getResult();
System.out.println(filename + "文件編寫完成");
}
}
}
