LSP Violation - MyDrawing Class

[jossanchcald]

The MyDrawing Class in the ex04 package violates twice the Liskov Substitution Principle, overriding the methods in a way that may affect the functioning of the system, it may lead to unexpected exceptions or restricted behavior. This errors should be fixed as you see fittable, but as a sugestion:

You should change the method:
@Override void selectLine(Line line) { if (!lines.contains(line)){ throw new RuntimeException("Invalid Line"); } if(line instanceof InnerSelectableLine){ InnerSelectableLine l = (InnerSelectableLine) line; l.isSelected = true; }else{ throw new RuntimeException("Invalid Line"); } }

For the LSP violation-free version:
` // FIXED VIOLATION #1
@OverRide
void selectLine(Line line) {
// Just exit the method and don't throw exceptions
if (!lines.contains(line)) {
return;
}

    if (line instanceof InnerSelectableLine) {
        InnerSelectableLine l = (InnerSelectableLine) line;
        l.isSelected = true;
    } else {
    // This is an assumption, you should change it as you see more fittable for the system
        line.setSelected(true);
    }
} `

And the method:
@Override void alignSelectedLinesToTheRight() { throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates. }

For the LSP violation-free version:
// FIXED VIOLATION #2 @Override void alignSelectedLinesToTheRight() { // This is an assumption, it should be the correct algorithm for (Line line : getSelectedLines()) { line.alignRight(); } }

So your class MyDrawing should result in:

`package org.afdemp.cb6.ex04;

import java.util.ArrayList;
import java.util.List;
import org.afdemp.cb6.ex03.geom.Line;
import org.afdemp.cb6.ex03.geom.Point;

public class MyDrawing extends Drawing {

@Override
Line addLine(int x1, int x2, int y) {
   Point p1 = new Point(x1, y);
   Point p2 = new Point(x2, y);
   //Line l1 =  new Line(p1,p2);
   //SelectableLine l1 = new SelectableLine(p1, p2, false);
   InnerSelectableLine l1 = new InnerSelectableLine(p1, p2, false);
   lines.add(l1);
   return l1;
}


// FIXED VIOLATION #1
@Override
void selectLine(Line line) {
// Just exit the method and don't throw exceptions
    if (!lines.contains(line)) {
        return;
    }

    if (line instanceof InnerSelectableLine) {
        InnerSelectableLine l = (InnerSelectableLine) line;
        l.isSelected = true;
    } else {
    // This is an assumption, you should change it as you see more fittable for the system
        line.setSelected(true);
    }
}


@Override
void alignSelectedLinesToTheLeft() {
    List<InnerSelectableLine> selectedLines = new ArrayList<>();
    
    int minX = Integer.MAX_VALUE;   
    for(Line line : lines){
        InnerSelectableLine l = (InnerSelectableLine) line;
        if (l.isSelected){
            minX = getMinX(minX, l);                
            selectedLines.add(l);
        }
    }
    
    for (InnerSelectableLine line : selectedLines) {            
        Point f = line.getFirstPoint();
        Point s = line.getSecondPoint();            
        int dist = Math.abs(f.getX() - s.getX());
        f.setX(minX);
        s.setX(minX + dist);
    }
}

// FIXED VIOLATION #2
@Override
void alignSelectedLinesToTheRight() {
// This is an assumption, it should be the correct algorithm
    for (Line line : getSelectedLines()) {
        line.alignRight();
    }
}

private static int getMinX(int x, Line l) {
    int m = Math.min(x, l.getFirstPoint().getX());
    return Math.min(m, l.getSecondPoint().getX());
}

private static class InnerSelectableLine extends Line {
    
    private boolean isSelected;
    
    private InnerSelectableLine(Point f, Point s, boolean selected) {
        super(f, s);
        isSelected = selected;

       }
    }
}`