Rectangle.java

// package inheritance;

public class Rectangle implements Shape {

	private double width;
	private double height;

	// constructs a new rectangle with the given dimensions
	public Rectangle(double width, double height) {
		this.width = width;
		this.height = height;
	}

	// returns the area of this rectangle
	public double getArea() {
		return width * height;
	}

	// returns the perimeter of this rectangle
	public double getPerimeter() {
		return 2.0 * (width + height);
	}
	
	
	@Override
	public boolean equals(Object obj) {

		if (obj == null) {
			return false;
		}

		if (obj.getClass() != this.getClass()) {
			return false;
		}

		final Rectangle rec = (Rectangle) obj;
		if ((Double.valueOf(this.width) == null) ? (Double.valueOf(rec.height) != null)
				: !((Double.valueOf(this.width)).equals(Double.valueOf(rec.width)))) {
			return false;
		}

		if (this.height != rec.height) {
			return false;
		}

		return true;
	}
	
	@Override
	public int hashCode() {

      // chose a random prime number for better hash functionality		
		int hash = 31;
		hash = 17 * hash + (Double.valueOf(this.width) != null ? Double.valueOf(this.width).hashCode() : 0);
		hash = (int) (17 * hash + this.height);
		return hash;
	}


	
	
}

Circle.java

// package inheritance;

public class Circle implements Shape {
	private double radius;

	// constructs a new circle with the given radius
	public Circle(double radius) {
		this.radius = radius;
	}

	// returns the area of this circle
	public double getArea() {
		return Math.PI * radius * radius;
	}

	// returns the perimeter of this circle
	public double getPerimeter() {
		return 2.0 * Math.PI * radius;
	}

	@Override
	public boolean equals(Object obj) {

		if (obj == null) {
			return false;
		}

		if (obj.getClass() != this.getClass()) {
			return false;
		}

		final Circle cir = (Circle) obj;

		if (this.radius != cir.radius) {
			return false;
		}

		return true;
	}

	@Override
	public int hashCode() {

		// chose a random prime number for better hash functionality
		int hash = 31;
		hash = 17 * hash + (Double.valueOf(this.radius) != null ? Double.valueOf(this.radius).hashCode() : 0);
		hash = (int) (17 * hash + this.radius);
		return hash;
	}
	

}

Triangle.java

// package inheritance;

public class Triangle implements Shape {
 private double a;
 private double b;
 private double c;

// constructs a new triangle with the given side lengths
 public Triangle(double a, double b, double c) {
 this.a = a;
 this.b = b;
 this.c = c;
 }
 // returns this triangle's area using Heron's formula
 public double getArea() {
 double s = (a + b + c) / 2.0;
 return Math.sqrt(s * (s - a) * (s - b) * (s - c));
 }

 // returns the perimeter of this triangle
 public double getPerimeter() {
 return a + b + c;
 }
 
 
 @Override
	public boolean equals(Object obj) {

		if (obj == null) {
			return false;
		}

		if (obj.getClass() != this.getClass()) {
			return false;
		}

		final Triangle tri = (Triangle) obj;
		
		if (!(Double.valueOf(this.a).equals(Double.valueOf(tri.a))) || !(Double.valueOf(this.b).equals(Double.valueOf(tri.b)))
				|| !(Double.valueOf(this.c).equals(Double.valueOf(tri.c)))) {
			return false;
		}


		return true;
	}
	
	@Override
	public int hashCode() {

   // chose a random prime number for better hash functionality		
		int hash = 31;
		hash = 17 * hash + (Double.valueOf(this.a) != null ? Double.valueOf(this.b).hashCode() : 0);
		hash = (int) (17 * hash + this.c);
		return hash;
	}
 
 }

CheckTwoShapes.java

public class CheckTwoShapes {

	public static void main(String[] args) {
		
		Rectangle rec = new Rectangle(4,8);
		Rectangle rec1 = new Rectangle(2,7);
		Rectangle rec2 = new Rectangle(4,8);
		
		Circle c1 = new Circle(7);
		Circle c2 = new Circle(4);
		Circle c3 = new Circle(4);
		
		Triangle tri = new Triangle(9,7,3);
		Triangle tri1 = new Triangle(3,4,8);
		Triangle tri2 = new Triangle(9,7,3);
		
		System.out.println(rec.equals(rec2));
		System.out.println(rec.equals(rec1));
		
		System.out.println(c3.equals(c2));
		System.out.println(c1.equals(c3));
		
		System.out.println(tri.equals(tri2));
		System.out.println(tri1.equals(tri2));
		
		
	}

}

Output:

true
false
true
false
true
false