用于读取不同文件格式的策略模式(Strategy pattern to read different file formats)
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();
}
}
}
我有一个问题，介绍了更多的文件格式，我们将为它们创建单独的类，但我必须更改TestStrategy类中的if else代码，以便为引入的文件模式创建新对象。
我们可以删除这个if else代码。任何建议。
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.
最满意答案
您可以使用将文件扩展名映射到实现的注册表。
public class Registry { static Map<String,FileReader> reg = new HashMap<String,FileReader>(); public static void register(String ext, FileReader fr ) { reg.put( ext, fr ); } }让新添加的实现注册自己，例如
public class XMLReader implements FileReader { static { Registry.register( "xml", new XMLReader() ); } .... public class ExcelReader implements FileReader { static { Registry.register( "xls", new ExcelReader() ); } ...那么您可以简单地在注册表中查找合适的实现，而不需要if或switch 。
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.
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