Lösningar till övning 2

public class Counter {
  private int val;

  public Counter() {
    reset();
  }

  public void count() {
    val++;
  }

  public void reset() {
    val = 0;
  }

  public int readValue() {
    return val;
  }
}

public static void main(String[] args) {
  if (args.length != 1) {
    System.out.println("Ange ett filnamn som programargument");
    return;
  }
  File fil = new File(args[0]);
  Scanner scanner = null;

  try {
    scanner = new Scanner(fil);

    Counter countOdd = new Counter();
    Counter countEven = new Counter();

    while (scanner.hasNext()) {
      int x = scanner.nextInt();
      if (x % 2 == 0) { // even number
        countEven.count();
      } else {  // x % 2 == 1, odd number
        countOdd.count();
      }
    }

    System.out.println("Filen innehåller " + countOdd.readValue() + " udda tal" +
                       " och " + countEven.readValue() + " jämna tal.");
  } catch (FileNotFoundException e) {
    System.out.println("Filen existerar inte.");
  } catch (InputMismatchException e) {
    System.out.println("Filen ska bara innehålla heltal.");
  } finally {
    if (scanner != null) scanner.close();
  }
}

public class FinSubset {

  public static class SetSizeMismatchException extends RuntimeException {
  }

  private boolean[] members;

  public FinSubset(int n) {
    members = new boolean[n];

    for (int i = 0; i < n; i++) {
      members[i] = false;
    }
  }

  public int universeSize() {
    return members.length;
  }

  public void add(int x) {
    members[x] = true;
  }

  public void remove(int x) {
    members[x] = false;
  }

  public boolean isMember(int x) {
    return members[x];
  }

  public int size() {
    int s = 0;
    // use enhanced for-loop instead of traditional (seel below) 
    for (boolean m : members) {
      if (m) s++;
    }
    // for (int i = 0; i < members.length; i++) {
    //   if (members[i]) s++;
    // }
    return s;
  }

  private void checkUniverseSizes(FinSubset s) {
    if (members.length != s.members.length) {
      throw new SetSizeMismatchException();
    }   
  }

  public boolean isSubsetOf(FinSubset s) {
    checkUniverseSizes(s);

    for (int i = 0; i < members.length; i++) {
      if (members[i] && !s.members[i]) return false;
    }
    return true;
  }

  public FinSubset union(FinSubset s) {
    checkUniverseSizes(s);

    FinSubset newSet = new FinSubset(members.length);
    for (int i = 0; i < members.length; i++) {
      if (isMember(i) || s.isMember(i)) {
        newSet.add(i);
      }
    }
    return newSet;
  }

  public FinSubset intersection(FinSubset s) {
    checkUniverseSizes(s);

    FinSubset newSet = new FinSubset(members.length);
    for (int i = 0; i < members.length; i++) {
      if (isMember(i) && s.isMember(i)) {
        newSet.add(i);
      }
    }
    return newSet;
  }

}

Se föregående kod.

private static FinSubset readSet(File fil) {
  Scanner scanner = null;
  FinSubset s = null;

  try {
    scanner = new Scanner(fil);

    int n = scanner.nextInt();

    s = new FinSubset(n);

    while (scanner.hasNext()) {
      int x = scanner.nextInt();
      s.add(x);
    }
  } catch (FileNotFoundException e) {
    System.out.println("Filen existerar inte.");
  } finally {
    if (scanner != null) scanner.close();
  }

  return s;
}

public static void main(String[] args) {
  FinSubset s1 = readSet(new File(args[0]));
  FinSubset s2 = readSet(new File(args[1]));
  FinSubset s3 = s1.intersection(s2);  // or s2.intersection(s1)

  PrintWriter writer = null;
  try {
    writer = new PrintWriter(new File(args[2]));

    writer.print(s3.universeSize() + " ");

    for (int i = 0; i < s3.universeSize(); i++) {
      if (s3.isMember(i)) {
        writer.print(i + " ");
      }
    }

  } catch (FileNotFoundException e) {
    System.out.println("Couldn't open output file.");
  } finally {
    if (writer != null) writer.close();
  }
} 

public class Point {
  private double x, y;

  public Point() {
    x = y = 0.0;
  }

  public Point(double x, double y) {
    this.x = x;
    this.y = y;
  }

  public Point(Point p) {
    x = p.x;
    y = p.y;
  }

  public double getX() {
    return x;
  }

  public double getY() {
    return y;
  }

  public void setX(double x) {
    this.x = x;
  } 

  public void setY(double y) {
    this.y = y;
  } 

  public void translate(double dx, double dy) {
    x += dx;
    y += dy;
  }

  public void rotate(Point center, double angle) {
    double relx = x - center.x;
    double rely = y - center.y;
    double cos = Math.cos(angle);
    double sin = Math.sin(angle);
    x = center.x + relx * cos + rely * sin;
    y = center.y + rely * cos - relx * sin;
  }

  public boolean equals(Point p) {
    return x == p.x && y == p.y;
  }
} 

public class Line {
  Point p1, p2;

  public Line(Point p1, Point p2) {
    this.p1 = new Point(p1);
    this.p2 = new Point(p2);
  }

  public boolean equals(Line l) {
    return p1.equals(l.p1) && p2.equals(l.p2) ||
           p2.equals(l.p1) && p1.equals(l.p2);
  }

  public double length() {
    double dx = p1.getX() - p2.getX();
    double dy = p1.getY() - p2.getY();
    return Math.sqrt(dx * dx + dy * dy);
  }

  public Point[] getPoints() {
    Point[] points = new Point[2];
    points[0] = new Point(p1);
    points[1] = new Point(p2);
    return points;
  }
}