Gfrktyl

I was asked to code a TextPad with following functionality:
display() – to display the entire content

display(n, m) – to display from line n to m

insert(n, text) – to insert text at line n

delete(n) – delete line n

delete(n, m) – delete from line n to m

copy(n, m) – copy contents from line n to m to clipboard

paste(n) – paste contents from clipboard to line n

undo() – undo last command

redo() – redo last command

They expected the textpad to be in memory (not as file). They also expected to handle error gracefully and the program to be menu driven.

Can someone please review the class structure implemented. Can it be improved so that code can be easily modified and extended?

public interface Command {



      void execute();



      void undo();



  }

package com.onedirect.oodesign.textpad;



public class PasteCommand implements Command {



  private TextPad textPad;



  private Integer line;



  public PasteCommand(TextPad textPad, Integer line){

    this.textPad = textPad;

    this.line = line;

  }



  @Override

  public void execute() {

    this.textPad.getLines().addAll(line, this.textPad.getClipBoard());

  }



  @Override

  public void undo() {

    for (int i = line; i < this.textPad.getClipBoard().size(); i++) {

      this.textPad.getLines().remove(i);

    }

  }





}

package com.onedirect.oodesign.textpad;



public class CopyCommand implements Command {



  private TextPad textPad;



  private Integer from;



  private Integer to;



  public CopyCommand(TextPad textPad, Integer from, Integer to) {

    this.textPad = textPad;

    this.from = from;

    this.to = to;

  }





  @Override

  public void execute() {

    this.textPad.setClipBoard(this.textPad.getLines().subList(from, to));

  }



  @Override

  public void undo() {



  }



}

package com.onedirect.oodesign.textpad;



import java.util.List;



public class DeleteCommand implements Command {





  private TextPad textPad;



  private Integer from;



  private Integer to;



  private List<String> lines;



  public DeleteCommand(TextPad textPad, Integer from, Integer to) {

    this.textPad = textPad;

    this.from = from;

    this.to =to;

  }



  @Override

  public void execute() {

    List<String> content = textPad.getLines();

    this.lines  = content.subList(from, to);

    for (int i = from; i < to && i<content.size(); i++) {

      content.remove(i);

    }

  }



  @Override

  public void undo() {

    List<String> content = textPad.getLines();

    content.addAll(from, this.lines);

  }

}

package com.onedirect.oodesign.textpad;



import java.util.List;



public class DisplayCommand  implements Command {





  private TextPad textPad;



  private int m;



  private int n;



  public DisplayCommand(TextPad textPad, int m, int n) {

    this.textPad = textPad;

    this.m = m;

    this.n = n;

  }

  public DisplayCommand(TextPad textPad) {

    this.textPad = textPad;

    this.m = 0;

    this.n = this.textPad.getLines().size();

  }



  @Override

  public void execute() {

    List<String> list = this.textPad.getLines();

    list.subList(m, n).forEach(System.out::println);

  }



  @Override

  public void undo() {



  }





}

package com.onedirect.oodesign.textpad;



public class InsertCommand implements Command{



  private TextPad textPad;



  private Integer line;



  private String text;



  public InsertCommand(TextPad textPad, Integer line, String text) {

    this.line = line;

    this.textPad = textPad;

    this.text = text;

  }



  @Override

  public void execute() {

    this.textPad.getLines().add(line, text);

  }



  @Override

  public void undo() {

    this.textPad.getLines().remove((int)line);

  }

}

package com.onedirect.oodesign.textpad;



import java.util.ArrayList;

import java.util.List;

import java.util.Stack;



public class TextPad {



  private List<String> lines;



  private Stack<Command> undo;



  private Stack<Command> redo;



  private List<String> clipBoard;



  public TextPad() {

    this.lines = new ArrayList<>();

    this.undo = new Stack<>();

    this.redo = new Stack<>();

    this.clipBoard = new ArrayList<>();

  }







  public List<String> getClipBoard() {

    return this.clipBoard;

  }



  public void setClipBoard(List<String> clipBoard) {

    this.clipBoard = clipBoard;

  }



  public List<String> getLines() {

    return lines;

  }



  public void display() {

    DisplayCommand displayCommand = new DisplayCommand(this);

    displayCommand.execute();

  }



  public void display(int m, int n) {

    DisplayCommand displayCommand = new DisplayCommand(this, m, n);

    displayCommand.execute();

  }



  public void insert(int n, String text) {

    clearRedo();

    InsertCommand insertCommand = new InsertCommand(this, n, text);

    insertCommand.execute();

    undo.push(insertCommand);

  }



  public void delete(int n) {

    delete(n, n);

  }



  public void delete(int n, int m) {

    clearRedo();

    DeleteCommand deleteCommand = new DeleteCommand(this, n, m);

    deleteCommand.execute();

    undo.push(deleteCommand);

  }



  public void copy(int n, int m) {

    clearRedo();

    CopyCommand copyCommand = new CopyCommand(this, n, m);

    copyCommand.execute();

  }



  public void paste(int n) {

    clearRedo();

    PasteCommand pasteCommand = new PasteCommand(this, n);

    pasteCommand.execute();

    undo.push(pasteCommand);

  }



  public void undo(){

    if(!undo.isEmpty()) {

      Command command = undo.pop();

      command.undo();

      redo.push(command);

    }

  }



  public void redo(){

    if(!redo.isEmpty()) {

      Command command = redo.pop();

      command.execute();

      undo.push(command);

    }

  }



  private void clearRedo() {

    while (!redo.isEmpty()) {

      redo.pop();

    }

  }



}