methodtostringandequals.java

卡内基梅隆大学的网上教程 ssd3第二单元源码

package unitTwo;

public class MethodtoStringAndequals {

	    /* Number of instances created */
	    private static int numberOfInstances = 0;

	    /* x coordinate of this point */
	    private int  x;

	    /* y coordinate of this point */
	    private int  y;

	     /*
			 * Test driver for class <code>Point</code>.
			 * 
			 * @param args not used
			 */
	    public static void main(String[] args) {

	    	MethodtoStringAndequals pointOne = new MethodtoStringAndequals(10, 100);
	    	MethodtoStringAndequals pointTwo = new MethodtoStringAndequals(-20, 200);
	    	MethodtoStringAndequals pointThree = new MethodtoStringAndequals(50, -20);
	    	System.out.println("before reset pointOne");
	    	System.out.println("x: " + pointOne.getX());
	        System.out.println("y: " + pointOne.getY());
	    	
	        pointOne.setX(-20);
	        pointOne.setY(200);
	        
	    	System.out.println("after reset pointOne");     
	        System.out.println("x: " + pointOne.getX());
	        System.out.println("y: " + pointOne.getY());

	        if (pointOne.equals(pointTwo)) {
	            System.out.println("pointOne and pointTwo are equal");
	        } else {
	            System.out.println("pointOne and pointTwo are different");
	        }

	        if (pointOne.equals(pointThree)) {
	            System.out.println("pointOne and pointThree are equal");
	        } else {
	            System.out.println("pointOne and pointThree are different");
	        }

	        System.out.println(pointOne);
	        System.out.println(pointTwo);
	        System.out.println(pointThree);
	        System.out.println();

	        System.out.println("Instances before PointTwo is created: " +
	        		MethodtoStringAndequals.getNumberOfInstances());

	    }

	    /**
		 * Creates a <code>Point</code> object and increments the number of
		 * instances.
		 * 
		 * @param initialX
		 *            the x coordinate
		 * @param initialY
		 *            the y coordinate
		 */
	    public MethodtoStringAndequals(int  initialX, int  initialY)  {

	        this.x = initialX;
	        this.y = initialY;

	        MethodtoStringAndequals.numberOfInstances++;
	    }

	    /**
		 * Returns the number of <code>Point</code> instances that have been
		 * created.
		 * 
		 * @return the number of <code>Point</code> instances that have been
		 *         created.
		 */
	    public static int  getNumberOfInstances()  {

	        return MethodtoStringAndequals.numberOfInstances;
	    }

	    /**
		 * Returns the x coordinate of this point.
		 * 
		 * @return the x coordinate of this point.
		 */
	    public int  getX()  {

	        return this.x;
	    }

	    /**
		 * Returns the y coordinate of this point.
		 * 
		 * @return the y coordinate of this point.
		 */
	    public int  getY()  {

	        return this.y;
	    }

	    /**
		 * Modifies the x coordinate of this point.
		 * 
		 * @param newX
		 *            the new x coordinate
		 */
	    public void  setX(int  newX)  {

	        this.x = newX;
	    }

	    /**
		 * Modifies the y coordinate of this point.
		 * 
		 * @param newY
		 *            the new y coordinate
		 */
	    public void  setY(int  newY)  {

	        this.y = newY;
	    }

	/**
	 * Overrides {@link Object#toString()}.
	 * <p>
	 * Returns a string representation of this <code>Point</code> object.
	 * </p>
	 * 
	 * @return a string representation of this <code>Point</code> object.
	 */
    public String  toString()  {

        return  "(" + getX() + "," + getY() + ")";
    }

    /**
     * Overrides {@link Object#equals(Object)}.
     * <p>
     * Two <code>Point</code> objects are equal if their x and y
     * coordinates are the same.
     * </p>
     *
     * @param object  object which this <code>Point</code> is
     *                compared.
     * @return  <code>true</code> if the x and y coordinates of
     *          this <code>Point</code> are equal to the x and y
     *          coordinates of the argument; <code>false</code>
     *          otherwise.
     */
    public boolean  equals(Object  object)  {

        if (object instanceof MethodtoStringAndequals) {

        	MethodtoStringAndequals point = (MethodtoStringAndequals) object;

            return point.getX() == getX() && point.getY() == getY();

        } else {

            return false;
        }
    }
}