Created
October 15, 2016 19:31
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Visitor Pattern
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| import java.util.ArrayList; | |
| import java.util.List; | |
| import java.util.stream.Collectors; | |
| import java.util.stream.Stream; | |
| public class VisitorPatternExample { | |
| public static void main(String[] args) { | |
| List<String> list = new ArrayList<String>(); | |
| //list.add("java"); | |
| list.add("pdf"); | |
| list.add("html"); | |
| list.forEach(file -> { | |
| FileOperator head = new Head(); | |
| FileUtil.fileIdentifier(file).doFileOperation(head); | |
| }); | |
| } | |
| } | |
| //Visitable | |
| interface ReadableFile { | |
| public String readNextLine(); | |
| public void doFileOperation(FileOperator operator); | |
| } | |
| class PdfFile implements ReadableFile { | |
| PdfFile(String fileName) { | |
| // Create instance of File | |
| } | |
| public String readNextLine() { | |
| return "Reading line from a PDF"; | |
| } | |
| @Override | |
| public void doFileOperation(FileOperator operator) { | |
| operator.processPdfFile(this); | |
| } | |
| public boolean isSecure() { | |
| return false; | |
| } | |
| } | |
| class HtmlFile implements ReadableFile { | |
| HtmlFile(String fileName) { | |
| // Create instance of File | |
| } | |
| public String readNextLine() { | |
| return "Reading line from a HTML"; | |
| } | |
| @Override | |
| public void doFileOperation(FileOperator operator) { | |
| operator.processHtmlFile(this); | |
| } | |
| } | |
| interface FileOperator{ | |
| public void processPdfFile(PdfFile file); | |
| public void processHtmlFile(HtmlFile file); | |
| } | |
| class Head implements FileOperator{ | |
| public void operation(PdfFile file) { | |
| file.readNextLine(); | |
| } | |
| @Override | |
| public void processPdfFile(PdfFile file) { | |
| if(file.isSecure()){ | |
| System.out.println("Can't read secure file"); | |
| }else{ | |
| System.out.println(file.readNextLine()); | |
| } | |
| } | |
| @Override | |
| public void processHtmlFile(HtmlFile file) { | |
| System.out.println(file.readNextLine()); | |
| } | |
| } | |
| class FileUtil { | |
| public static ReadableFile fileIdentifier(String fileName) { | |
| if (fileName.toString().contains("pdf")) | |
| return new PdfFile(fileName); | |
| else if (fileName.toString().contains("html")) | |
| return new HtmlFile(fileName); | |
| return null; | |
| } | |
| } |
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