Java/Design Pattern/Bridge Pattern
Bridge Pattern 1
<source lang="java">
/* Software Architecture Design Patterns in Java by Partha Kuchana Auerbach Publications
- /
import java.io.BufferedReader; import java.io.DataOutputStream; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStreamReader; import java.util.Vector; public class BridgePatternClient {
public static void main(String[] args) {
//Create an appropriate implementer object
MessageLogger logger = new FileLogger();
//Choose required interface object and
// configure it with the implementer object
Message msg = new EncryptedMessage(logger);
msg.log("Test Message");
}
} class ConsoleLogger implements MessageLogger {
public void logMsg(String msg) {
System.out.println(msg);
}
} class EncryptedMessage implements Message {
private MessageLogger logger;
public EncryptedMessage(MessageLogger l) {
logger = l;
}
public void log(String msg) {
String str = preProcess(msg);
logger.logMsg(str);
}
private String preProcess(String msg) {
msg = msg.substring(msg.length() - 1)
+ msg.substring(0, msg.length() - 1);
return msg;
};
} class FileLogger implements MessageLogger {
public void logMsg(String msg) {
FileUtil futil = new FileUtil();
futil.writeToFile("log.txt", msg, true, true);
}
} class MiscUtil {
public static boolean hasDuplicates(Vector v) {
int i = 0;
int j = 0;
boolean duplicates = false;
for (i = 0; i < v.size() - 1; i++) {
for (j = (i + 1); j < v.size(); j++) {
if (v.elementAt(i).toString().equalsIgnoreCase(
v.elementAt(j).toString())) {
duplicates = true;
}
}
}
return duplicates;
}
public static Vector removeDuplicates(Vector s) {
int i = 0;
int j = 0;
boolean duplicates = false;
Vector v = new Vector();
for (i = 0; i < s.size(); i++) {
duplicates = false;
for (j = (i + 1); j < s.size(); j++) {
if (s.elementAt(i).toString().equalsIgnoreCase(
s.elementAt(j).toString())) {
duplicates = true;
}
}
if (duplicates == false) {
v.addElement(s.elementAt(i).toString().trim());
}
}
return v;
}
public static Vector removeDuplicateDomains(Vector s) {
int i = 0;
int j = 0;
boolean duplicates = false;
String str1 = "";
String str2 = "";
Vector v = new Vector();
for (i = 0; i < s.size(); i++) {
duplicates = false;
for (j = (i + 1); j < s.size(); j++) {
str1 = "";
str2 = "";
str1 = s.elementAt(i).toString().trim();
str2 = s.elementAt(j).toString().trim();
if (str1.indexOf("@") > -1) {
str1 = str1.substring(str1.indexOf("@"));
}
if (str2.indexOf("@") > -1) {
str2 = str2.substring(str2.indexOf("@"));
}
if (str1.equalsIgnoreCase(str2)) {
duplicates = true;
}
}
if (duplicates == false) {
v.addElement(s.elementAt(i).toString().trim());
}
}
return v;
}
public static boolean areVectorsEqual(Vector a, Vector b) {
if (a.size() != b.size()) {
return false;
}
int i = 0;
int vectorSize = a.size();
boolean identical = true;
for (i = 0; i < vectorSize; i++) {
if (!(a.elementAt(i).toString().equalsIgnoreCase(b.elementAt(i)
.toString()))) {
identical = false;
}
}
return identical;
}
public static Vector removeDuplicates(Vector a, Vector b) {
int i = 0;
int j = 0;
boolean present = true;
Vector v = new Vector();
for (i = 0; i < a.size(); i++) {
present = false;
for (j = 0; j < b.size(); j++) {
if (a.elementAt(i).toString().equalsIgnoreCase(
b.elementAt(j).toString())) {
present = true;
}
}
if (!(present)) {
v.addElement(a.elementAt(i));
}
}
return v;
}
}// end of class class FileUtil {
DataOutputStream dos;
/*
* Utility method to write a given text to a file
*/
public boolean writeToFile(String fileName, String dataLine,
boolean isAppendMode, boolean isNewLine) {
if (isNewLine) {
dataLine = "\n" + dataLine;
}
try {
File outFile = new File(fileName);
if (isAppendMode) {
dos = new DataOutputStream(new FileOutputStream(fileName, true));
} else {
dos = new DataOutputStream(new FileOutputStream(outFile));
}
dos.writeBytes(dataLine);
dos.close();
} catch (FileNotFoundException ex) {
return (false);
} catch (IOException ex) {
return (false);
}
return (true);
}
/*
* Reads data from a given file
*/
public String readFromFile(String fileName) {
String DataLine = "";
try {
File inFile = new File(fileName);
BufferedReader br = new BufferedReader(new InputStreamReader(
new FileInputStream(inFile)));
DataLine = br.readLine();
br.close();
} catch (FileNotFoundException ex) {
return (null);
} catch (IOException ex) {
return (null);
}
return (DataLine);
}
public boolean isFileExists(String fileName) {
File file = new File(fileName);
return file.exists();
}
public boolean deleteFile(String fileName) {
File file = new File(fileName);
return file.delete();
}
/*
* Reads data from a given file into a Vector
*/
public Vector fileToVector(String fileName) {
Vector v = new Vector();
String inputLine;
try {
File inFile = new File(fileName);
BufferedReader br = new BufferedReader(new InputStreamReader(
new FileInputStream(inFile)));
while ((inputLine = br.readLine()) != null) {
v.addElement(inputLine.trim());
}
br.close();
} // Try
catch (FileNotFoundException ex) {
//
} catch (IOException ex) {
//
}
return (v);
}
/*
* Writes data from an input vector to a given file
*/
public void vectorToFile(Vector v, String fileName) {
for (int i = 0; i < v.size(); i++) {
writeToFile(fileName, (String) v.elementAt(i), true, true);
}
}
/*
* Copies unique rows from a source file to a destination file
*/
public void copyUniqueElements(String sourceFile, String resultFile) {
Vector v = fileToVector(sourceFile);
v = MiscUtil.removeDuplicates(v);
vectorToFile(v, resultFile);
}
} // end FileUtil interface Message {
public void log(String msg);
} interface MessageLogger {
public void logMsg(String msg);
} class TextMessage implements Message {
private MessageLogger logger;
public TextMessage(MessageLogger l) {
logger = l;
}
public void log(String msg) {
String str = preProcess(msg);
logger.logMsg(str);
}
private String preProcess(String msg) {
return msg;
};
}
</source>
Bridge pattern in Java
<source lang="java">
/* The Design Patterns Java Companion Copyright (C) 1998, by James W. Cooper IBM Thomas J. Watson Research Center
- /
import java.awt.BorderLayout; import java.awt.Dimension; import java.awt.GridLayout; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import java.io.IOException; import java.io.RandomAccessFile; import java.util.Vector; import javax.swing.AbstractListModel; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JList; import javax.swing.JPanel; import javax.swing.JScrollPane; import javax.swing.JTable; import javax.swing.UIManager; import javax.swing.UnsupportedLookAndFeelException; import javax.swing.event.ListSelectionEvent; import javax.swing.event.ListSelectionListener; import javax.swing.event.TableModelListener; import javax.swing.table.TableModel; public class productDisplay extends JFrame {
public productDisplay() {
super("The Java Factory-- Products");
setLF(); //set look and feel
setCloseClick(); //set close on window close click
InputFile f = new InputFile("products.txt");
Vector prod = new Vector();
//read in product list
String s = f.readLine();
while (s != null) {
prod.addElement(s);
s = f.readLine();
}
JPanel p = new JPanel();
getContentPane().add(p);
p.setLayout(new GridLayout(1, 2));
JPanel pleft = new JPanel();
JPanel pright = new JPanel();
p.add(pleft);
p.add(pright);
pleft.setLayout(new BorderLayout());
pright.setLayout(new BorderLayout());
//add in customer view as list box
pleft.add("North", new JLabel("Customer view"));
pleft.add("Center", new productList(prod));
//add in execute view as table
pright.add("North", new JLabel("Executive view"));
pright.add("Center", new productTable(prod));
setSize(new Dimension(400, 300));
setVisible(true);
}
//-----------------------------------------
private void setCloseClick() {
//create window listener to respond to window close click
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
}
//------------------------------------------
private void setLF() {
// Force SwingApp to come up in the System L&F
String laf = UIManager.getSystemLookAndFeelClassName();
try {
UIManager.setLookAndFeel(laf);
} catch (UnsupportedLookAndFeelException exc) {
System.err.println("Warning: UnsupportedLookAndFeel: " + laf);
} catch (Exception exc) {
System.err.println("Error loading " + laf + ": " + exc);
}
}
//---------------------------------------------
static public void main(String argv[]) {
new productDisplay();
}
} class InputFile {
RandomAccessFile f = null;
boolean errflag;
String s = null;
public InputFile(String fname) {
errflag = false;
try {
//open file
f = new RandomAccessFile(fname, "r");
} catch (IOException e) {
//print error if not found
System.out.println("no file found");
errflag = true; //and set flag
}
}
//-----------------------------------------
public boolean checkErr() {
return errflag;
}
//-----------------------------------------
public String read() {
//read a single field up to a comma or end of line
String ret = "";
if (s == null) //if no data in string
{
s = readLine(); //read next line
}
if (s != null) //if there is data
{
s.trim(); //trim off blanks
int i = s.indexOf(","); //find next comma
if (i <= 0) {
ret = s.trim(); //if no commas go to end of line
s = null; //and null out stored string
} else {
ret = s.substring(0, i).trim(); //return left of comma
s = s.substring(i + 1); //save right of comma
}
} else
ret = null;
return ret; //return string
}
//-----------------------------------------
public String readLine() {
//read in a line from the file
s = null;
try {
s = f.readLine(); //could throw error
} catch (IOException e) {
errflag = true;
System.out.println("File read error");
}
return s;
}
//-----------------------------------------
public void close() {
try {
f.close(); //close file
} catch (IOException e) {
System.out.println("File close error");
errflag = true;
}
}
//-----------------------------------------
} class productList extends JawtList {
public productList(Vector products) {
super(products.size()); //for compatibility
for (int i = 0; i < products.size(); i++) {
//take each strig apart and keep only
//the product names, discarding the quntities
String s = (String) products.elementAt(i);
int index = s.indexOf("--"); //separate qty from name
if (index > 0)
add(s.substring(0, index));
else
add(s);
}
}
} class productTable extends JScrollPane {
JTable table;
public productTable(Vector list) {
table = new JTable(new prodModel(list));
getViewport().add(table);
}
} class prodModel implements TableModel {
int rows, columns;
Vector prodNames, quantities;
public prodModel(Vector products) {
rows = products.size();
columns = 2;
prodNames = new Vector();
quantities = new Vector();
for (int i = 0; i < products.size(); i++) {
String s = (String) products.elementAt(i);
int index = s.indexOf("--"); //separate qty from name
if (index > 0) {
prodNames.addElement(s.substring(0, index));
quantities.addElement(s.substring(index + 2).trim());
} else
prodNames.addElement(s);
}
}
public int getColumnCount() {
return columns;
}
public int getRowCount() {
return rows;
}
public Object getValueAt(int r, int c) {
switch (c) {
case 0:
return prodNames.elementAt(r);
case 1:
return quantities.elementAt(r);
default:
return prodNames.elementAt(r);
}
}
public Class getColumnClass(int c) {
return (new String("")).getClass();
}
public boolean isCellEditable(int r, int c) {
return false;
}
public String getColumnName(int c) {
return "";
}
public void setValueAt(Object obj, int r, int c) {
}
public void addTableModelListener(TableModelListener tbm) {
}
public void removeTableModelListener(TableModelListener tbm) {
}
} //this is a simple adapter class to //convert List awt methods to Swing methods class JawtList extends JScrollPane implements ListSelectionListener, awtList {
private JList listWindow;
private JListData listContents;
//-----------------------------------------
public JawtList(int rows) {
listContents = new JListData();
listWindow = new JList(listContents);
listWindow.setPrototypeCellValue("Abcdefg Hijkmnop");
getViewport().add(listWindow);
}
//-----------------------------------------
public void add(String s) {
listContents.addElement(s);
}
//-----------------------------------------
public void remove(String s) {
listContents.removeElement(s);
}
//-----------------------------------------
public String[] getSelectedItems() {
Object[] obj = listWindow.getSelectedValues();
String[] s = new String[obj.length];
for (int i = 0; i < obj.length; i++)
s[i] = obj[i].toString();
return s;
}
//-----------------------------------------
public void valueChanged(ListSelectionEvent e) {
}
} // ========================================= class JListData extends AbstractListModel {
private Vector data;
//-----------------------------------------
public JListData() {
data = new Vector();
}
//-----------------------------------------
public int getSize() {
return data.size();
}
//-----------------------------------------
public Object getElementAt(int index) {
return data.elementAt(index);
}
//-----------------------------------------
public void addElement(String s) {
data.addElement(s);
fireIntervalAdded(this, data.size() - 1, data.size());
}
//-----------------------------------------
public void removeElement(String s) {
data.removeElement(s);
fireIntervalRemoved(this, 0, data.size());
}
} interface awtList {
public void add(String s); public void remove(String s); public String[] getSelectedItems();
} //products.txt /* Brass plated widgets --1,000,076 Furled frammis --75,000 Detailed rat brushes --700 Zero-based hex dumps--80,000 Anterior antelope collars --578 Washable softwear --789,000 Steel-toed wing-tips --456,666
- /
</source>
Bridge Pattern in Java 3
<source lang="java">
//[C] 2002 Sun Microsystems, Inc.--- import java.util.ArrayList; public class RunBridgePattern {
public static void main(String [] arguments){
System.out.println("Example for the Bridge pattern");
System.out.println();
System.out.println("This example divides complex behavior among two");
System.out.println(" classes - the abstraction and the implementation.");
System.out.println();
System.out.println("In this case, there are two classes which can provide the");
System.out.println(" abstraction - BaseList and OrnamentedList. The BaseList");
System.out.println(" provides core funtionality, while the OrnamentedList");
System.out.println(" expands on the model by adding a list character.");
System.out.println();
System.out.println("The OrderedListImpl class provides the underlying storage");
System.out.println(" capability for the list, and can be flexibly paired with");
System.out.println(" either of the classes which provide the abstraction.");
System.out.println("Creating the OrderedListImpl object.");
ListImpl implementation = new OrderedListImpl();
System.out.println("Creating the BaseList object.");
BaseList listOne = new BaseList();
listOne.setImplementor(implementation);
System.out.println();
System.out.println("Adding elements to the list.");
listOne.add("One");
listOne.add("Two");
listOne.add("Three");
listOne.add("Four");
System.out.println();
System.out.println("Creating an OrnamentedList object.");
OrnamentedList listTwo = new OrnamentedList();
listTwo.setImplementor(implementation);
listTwo.setItemType("+");
System.out.println();
System.out.println("Creating an NumberedList object.");
NumberedList listThree = new NumberedList();
listThree.setImplementor(implementation);
System.out.println();
System.out.println("Printing out first list (BaseList)");
for (int i = 0; i < listOne.count(); i++){
System.out.println("\t" + listOne.get(i));
}
System.out.println();
System.out.println("Printing out second list (OrnamentedList)");
for (int i = 0; i < listTwo.count(); i++){
System.out.println("\t" + listTwo.get(i));
}
System.out.println();
System.out.println("Printing our third list (NumberedList)");
for (int i = 0; i < listThree.count(); i++){
System.out.println("\t" + listThree.get(i));
}
}
} interface ListImpl{
public void addItem(String item); public void addItem(String item, int position); public void removeItem(String item); public int getNumberOfItems(); public String getItem(int index); public boolean supportsOrdering();
} class BaseList{
protected ListImpl implementor;
public void setImplementor(ListImpl impl){
implementor = impl;
}
public void add(String item){
implementor.addItem(item);
}
public void add(String item, int position){
if (implementor.supportsOrdering()){
implementor.addItem(item, position);
}
}
public void remove(String item){
implementor.removeItem(item);
}
public String get(int index){
return implementor.getItem(index);
}
public int count(){
return implementor.getNumberOfItems();
}
} class NumberedList extends BaseList{
public String get(int index){
return (index + 1) + ". " + super.get(index);
}
} class OrderedListImpl implements ListImpl{
private ArrayList items = new ArrayList();
public void addItem(String item){
if (!items.contains(item)){
items.add(item);
}
}
public void addItem(String item, int position){
if (!items.contains(item)){
items.add(position, item);
}
}
public void removeItem(String item){
if (items.contains(item)){
items.remove(items.indexOf(item));
}
}
public boolean supportsOrdering(){
return true;
}
public int getNumberOfItems(){
return items.size();
}
public String getItem(int index){
if (index < items.size()){
return (String)items.get(index);
}
return null;
}
} class OrnamentedList extends BaseList{
private char itemType;
public char getItemType(){ return itemType; }
public void setItemType(char newItemType){
if (newItemType > " "){
itemType = newItemType;
}
}
public String get(int index){
return itemType + " " + super.get(index);
}
}
</source>
