کلاس های ابستراکت (abstract) در جاوا

public abstract class MyAbstractClass{ ... }

public abstract class MyAbstractClass{ ... public abstract myAbstractMethod(); ... }

public abstract class GeometricShape { private final Date dateCreated = new Date(); private String color; private boolean filled; public GeometricShape(String color, boolean filled){ this.color = color; this.filled = filled; } public String getColor() { return color; } public void setColor(String color) { this.color = color; } public Date getDateCreated() { return dateCreated; } public boolean isFilled() { return filled; } public void setFilled(boolean filled) { this.filled = filled; } //تعریف متد های مساحت و محیط به صورت ابستراکت public abstract double getArea(); public abstract double getPerimeter(); @Override public String toString() { if(this instanceof Circle) return "Circle: created on " + getDateCreated().toString() + "\n" + " area: " + getArea() + " perimeter " + getPerimeter(); else return "Rectangle: created on " + getDateCreated().toString() + "\n" + " area: " + getArea() + " perimeter: " + getPerimeter(); } } class Circle extends GeometricShape{ private double radius; public Circle(double radius, String color, boolean filled){ super(color, filled); this.radius = radius; } public Circle(double radius){ this(radius, "white", false); } public double getRadius() { return radius; } public void setRadius(double radius) { this.radius = radius; } //پیاده سازی کامل متد های مساحت و محیط @Override public double getArea(){ return Math.PI * radius * radius; } @Override public double getPerimeter(){ return 2 * Math.PI * radius; } @Override public boolean equals(Object obj) { if (obj instanceof Circle) return ((Circle) obj).radius == this.radius; return false; } } class Rectangle extends GeometricShape{ private double width; private double height; public Rectangle(double width , double height, String color, boolean filled){ super(color, filled); this.width = width; this.height = height; } public Rectangle(){ this(1.0, 1.0, "White", true); } public double getWidth() { return width; } public void setWidth(double width) { this.width = width; } public double getHeight() { return height; } public void setHeight(double height) { this.height = height; } //پیاده سازی کامل متد های مساحت و محیط @Override public double getArea(){ return width * height; } @Override public double getPerimeter(){ return (width + height) * 2; } @Override public String toString() { return "Rectangle: created on " + getDateCreated().toString() + "\n" + "width: " + getWidth() + " height: " + getHeight() + " area: " + getArea() + " perimeter: " + getPerimeter(); } @Override public boolean equals(Object obj) { if (obj instanceof Rectangle){ Rectangle r = (Rectangle) obj; return r.width == this.width && r.height == this.height; } return false; } }

public static void main(String[] args){ GeometricShape circle = new Circle(); System.out.println(circle.toString()); GeometricShape rectangle = new Rectangle(); System.out.println(rectangle.toString()); }