public interface FileReader {
void readFile();
void writeFile();
}
public class XMLReader implements FileReader {
@Override
public void readFile() {
System.out.println("Hellp i am read");
}
@Override
public void writeFile() {
System.out.println("Hello i am write");
}
}
public class ExcelReader implements FileReader {
@Override
public void readFile() {
System.out.println("Hellp i am read");
}
@Override
public void writeFile() {
System.out.println("Hello i am write");
}
}
public class Context {
FileReader reader ;
public Context(FileReader reader) {
super();
this.reader = reader;
}
public void executeRead(){
reader.readFile();
}
}
public class TestStrategy {
public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.println(args[0]);
String s=args[0];
String[] a=s.split("\\.");
if(a[1].equals("csv")){
new Context(new XMLReader()).executeRead();
}else{
new Context(new ExcelReader()).executeRead();
}
}
}
I have a concern more file format are introduced we will create separate class for them but i have to change the if else code in TestStrategy class to create new object for the file pattern introduced.
Can we remove this if else code .Any suggestions.
You could use a registry that maps a files extension to the implementation.
public class Registry {
static Map<String,FileReader> reg = new HashMap<String,FileReader>();
public static void register(String ext, FileReader fr ) {
reg.put( ext, fr );
}
}
and let newly added implementation register themself e.g.
public class XMLReader implements FileReader {
static {
Registry.register( "xml", new XMLReader() );
}
....
public class ExcelReader implements FileReader {
static {
Registry.register( "xls", new ExcelReader() );
}
...
then you could simply lookup the registry for a suitable implementation with no if or switch required.