java软件体系设计模式---享元

概念：

a,内在信息：对象的内在信息是独立与对象所处环境的

b，外部信息：一个对象的外部信息是与对象所处华宁有关的，并且随着环境的变化而有所不同。

享元应用场合：

该应用需要创建大量的对象，而这些对象只有部分参数是一致的。创建和维护这么多对象的代价是非常昂贵的，需要消耗大量的内存。

享元模式建议将所有的内在共同数据分离出来，建立一个单独的对象，也就是享元。这样就可以节省可观的内存以及时间开销。

实例：

它用于打印一家大型组织中所有雇员的名片数据，该组织拥有四个主要的分区办事处。

名片格式：

（外部数据）

《雇员姓名》

《头衔》

（内部数据）

《公司名称》

《分区办事处地址》

《城市》《州》《压缩码》

public interface FlyweightIntr {

public String getCompany();

public String getAddress();

public String getCity();

public String getState();

public String getZip();

}

import java.util.*;

// singleton Flyweight Factory

public class FlyweightFactory {

private HashMap lstFlyweight;

private static FlyweightFactory factory =

new FlyweightFactory();

private FlyweightFactory() {

lstFlyweight = new HashMap();

}

public synchronized FlyweightIntr getFlyweight(

String divisionName) {

if (lstFlyweight.get(divisionName) == null) {

FlyweightIntr fw = new Flyweight(divisionName);

lstFlyweight.put(divisionName, fw);

return fw;

} else {

return (FlyweightIntr) lstFlyweight.get(divisionName);

}

}

public static FlyweightFactory getInstance() {

return factory;

}

//Inner flyweight class

private class Flyweight implements FlyweightIntr {

private String company;

private String address;

private String city;

private String state;

private String zip;

private void setValues(String cmp, String addr,

String cty, String st, String zp) {

company = cmp;

address = addr;

city = cty;

state = st;

zip = zp;

}

private Flyweight(String division) {

// values are hard coded

//for simplicity

if (division.equals("North")) {

setValues("CMP","addr1", "cty1","st1","10000");

}

if (division.equals("South")) {

setValues("CMP","addr2", "cty2","st2","20000");

}

if (division.equals("East")) {

setValues("CMP","addr3", "cty3","st3","30000");

}

if (division.equals("West")) {

setValues("CMP","addr4", "cty4","st4","40000");

}

}

public String getCompany() {

return company;

}

public String getAddress() {

return address;

}

public String getCity() {

return city;

}

public String getState() {

return state;

}

public String getZip() {

return zip;

}

}// end of Flyweight

}// end of FlyweightFactory

public class VCard {

String name;

String title;

FlyweightIntr objFW;

public VCard(String n, String t, FlyweightIntr fw) {

name = n;

title = t;

objFW = fw;

}

public void print() {

System.out.println(name);

System.out.println(title);

System.out.println(objFW.getAddress() + "-" +

objFW.getCity() + "-" +

objFW.getState() + "-" +

objFW.getZip());

System.out.println("----------------");

}

}

import java.io.*;

import java.util.*;

public class FileUtil {

DataOutputStream dos;

public String OutputToFile(String FileName, String DataLine,

boolean AppendMode, boolean NewLine) {

if ((FileExists(FileName)) && (AppendMode == false)) {

try {

String tempFile =

FileName + new Date().getTime();

File OutFile = new File(tempFile);

dos = new DataOutputStream(

new FileOutputStream(OutFile));

dos.writeBytes(DataLine);

dos.close();

DeleteFile(FileName);

OutFile.renameTo(new File(FileName));

} catch (FileNotFoundException ex) {

//

System.out.println(

" File Utility OutputToFile ERROR=" +

ex.getMessage());

System.exit(1);

}

catch (IOException ex) {

//

System.out.println(

" File Utility OutputToFile ERROR=" +

ex.getMessage());

System.exit(1);

}

} else {

if (NewLine) {

DataLine = "\n" + DataLine;

}

try {

File OutFile = new File(FileName);

if (AppendMode) {

dos = new DataOutputStream(

new FileOutputStream(FileName, true));

} else {

dos = new DataOutputStream(

new FileOutputStream(OutFile));

}

dos.writeBytes(DataLine);

dos.close();

} catch (FileNotFoundException ex) {

//

System.out.println(

" File Utility OutputToFile ERROR=" +

ex.getMessage());

System.exit(1);

}

catch (IOException ex) {

//

System.out.println(

" File Utility OutputToFile ERROR=" +

ex.getMessage());

System.exit(1);

}

} // If-Else

return ("Success");

}

public String ReadFromFile(String FileName) {

String DataLine = "";

try {

File InFile = new File(FileName);

BufferedReader dos = new BufferedReader(

new InputStreamReader(

new FileInputStream(InFile)));

DataLine = dos.readLine();

dos.close();

} catch (FileNotFoundException ex) {

//

System.out.println(

" File Utility ReadFromFile ERROR=" +

ex.getMessage());

System.exit(1);

}

catch (IOException ex) {

//

System.out.println(

" File Utility ReadFromFile ERROR=" +

ex.getMessage());

System.exit(1);

}

return (DataLine);

}

public boolean FileExists(String FileName) {

File InFile = new File(FileName);

return InFile.exists();

}

public boolean DeleteFile(String FileName) {

File InFile = new File(FileName);

return InFile.delete();

}

public Vector FileToVector(String FileName) {

Vector v = new Vector();

String inputLine;

try {

File InFile = new File(FileName);

BufferedReader din = new BufferedReader(

new InputStreamReader(

new FileInputStream(InFile)));

while ((inputLine = din.readLine()) != null) {

v.addElement(inputLine);

}

din.close();

} // Try

catch (FileNotFoundException ex) {

//

System.out.println(

" File Utility FiletoVector ERROR=" +

ex.getMessage());

}

catch (IOException ex) {

//

System.out.println(

" File Utility FiletoVector ERROR=" +

ex.getMessage());

}

return (v);

}

public void VectorToFile(Vector v, String FileName) {

for (int i = 0; i < v.size(); i++) {

OutputToFile(FileName, (String) v.elementAt(i), true,

true);

}

}

}// end of class

import java.io.*;

import java.util.*;

public class FlyweightTest {

public static void main(String[] args) throws Exception {

Vector empList = initialize();

FlyweightFactory factory =

FlyweightFactory.getInstance();

for (int i = 0; i < empList.size(); i++) {

String s = (String) empList.elementAt(i);

StringTokenizer st = new StringTokenizer(s, ",");

String name = st.nextToken();

String title = st.nextToken();

String division = st.nextToken();

FlyweightIntr flyweight =

factory.getFlyweight(division);

//associate the flyweight

//with the extrinsic data object.

VCard card = new VCard(name, title, flyweight);

card.print();

}

}

private static Vector initialize() {

//for simplicity values are being hardcoded.

Vector v = new Vector();

v.add("name1,title1,North");

v.add("name2,title2,South");

v.add("name3,title1,North");

v.add("name4,title3,East");

v.add("name5,title4,East");

v.add("name6,title2,East");

v.add("name7,title1,West");

v.add("name8,title3,West");

v.add("name9,title1,West");

v.add("name10,title6,South");

v.add("name11,title5,North");

v.add("name12,title1,North");

return v;

}

}

文档与源代码下载地址:http://download.csdn.net/detail/hnzhangshilong/3685894