Mega Code Archive
Bridge Pattern in Java 3
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//[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);
}
}
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