Question

This is my code that i need to finish.
In BoxRegion.java
I have no idea how to create the constructor.
I tried to use super(x,y) but It is hard to apply. 
And Also In BoxRegionHashTable,
I don't know how to create displayAnnotation 



BoxRegion.java
------------------------------------------------
public final class BoxRegion {
    final Point2D p1;
    final Point2D p2;

    /**
     * Create a new 3D point with given x, y and z values
     *
     * @param x1, y1 are the x,y coordinates for point
     *            defining a corner of the BoxRegion
     * @param x2, y2 are coordinates for the other corner
     */
    public BoxRegion(int x1, int y1, int x2, int y2) {
        // TODO: assign values to p1 and p2
       
    }

    /**
     * Return a string describing the 3D point
     */
    public String toString() {
        return "(" + p1.x + ", " + p1.y + "), (" + +p2.x + ", " + p2.y + ")";
    }


    /**
     * Override the default hashcode method
     */
    // TODO: write hashCode method
    int hashcode() {
        int hash = 17;
        hash = hash * 31 + p1.hashCode();
        hash = hash * 31 + p2.hashCode();
        return hash;

    }

    /**
     * Override the default equals method.
     * Two BoxRegion objects equal if the coordinates
     * of their opposing points are equal.
     */
    // TODO: Write equals method
    public boolean equals(Object obj) {
        if (obj instanceof Point2D == false){
            return false;
        }
        BoxRegion b = (BoxRegion) obj;
        if ( p1!= b.p1 || p2 != b.p2) {
            return false;
        }
        return true;
    }
}

-----------------------------------------------------

Point2D

** 
 * Object for storing a 2D point.
 * 
 * @author rlsummerscales
 *
 */
public final class Point2D {
    final int x;
    final int y;
    
    /** Create a new 2D point with given x and y values 
      * 
      * @param xValue is the value for the x-coordinate
      * @param yValue is the value for the y-coordinate
      */
    public Point2D(int xValue, int yValue) {
        x = xValue;
        y = yValue;
    }
    
    /** Return a string describing the 2D point */
    public String toString() {
        return "(" + x + ", " + y + ")";
    }
    
    
    /** Override the default hashcode method */
    public int hashCode(){
        int hash = 13;
        hash = 31*hash + ((Integer) x).hashCode();
        hash = 31*hash + ((Integer) y).hashCode();
        return hash;
    }
    
    /** Override the default equals method.
      * Two Point2D objects equal if their values are equal.
      */
    public boolean equals(Object obj) {
        if (obj instanceof Point2D == false){
            return false;
        }
        Point2D p = (Point2D) obj;
        if (x != p.x || y != p.y) {
            return false;
        }
        return true;
    }
    
}

BoxRegionHashTable

------------------------------------------------------------------------

public class BoxRegionHashTable {
    /** Output the annotation for a given BoxRegion
      * 
      * @param key is the BoxRegion
      * @param annotationMap is a map of annotation string for a set of points
      */
    // TODO: Write function displaAnnotation.
    // It should output the annotation for a given key for a given HashMap.
    // if point is not in hash table, display message stating that it has no annotation

    
    /** Test the equals and hashCode implementations in BoxRegion
      * @param args is an array of command line arguments
      */
    public static void main(String[] args) {
        // TODO: Create hash map of BoxRegion objects with their annotations as keys
        
        // TODO: Insert BoxRegions and corresponding strings into table
        
        // the following should be successful
        displayAnnotation(new BoxRegion(45, 237, 60, 300), annotationMap);
        displayAnnotation(new BoxRegion(1175, 140, 350, 418), annotationMap);
        displayAnnotation(new BoxRegion(2000, 0, 1700, 3000), annotationMap);
        displayAnnotation(new BoxRegion(1460, 1030, 819, 1420), annotationMap);
        
        // the following should fail
        displayAnnotation(new BoxRegion(237, 45, 300, 60), annotationMap);
        displayAnnotation(new BoxRegion(0, 0, 0, 0), annotationMap);
    }
    
}

Answer 1

• I have pasted the code and screenshot of successful run below.
• In case of any doubts just comment down.

--------------------------------------Screenshot--------------------------------------

ksmukta:4. - javac *.java && java BoxRegionHashTable Annotation: Box1 It has no annotation It has no annotation It has no annotation It has no annotation It has no annotation

--------------------------------------BoxRegion.java--------------------------------------

public class BoxRegion {
final Point2D p1;
final Point2D p2;

/**
* Create a new 3D point with given x, y and z values
*
* @param x1, y1 are the x,y coordinates for point
* defining a corner of the BoxRegion
* @param x2, y2 are coordinates for the other corner
*/
public BoxRegion(int x1, int y1, int x2, int y2) {
p1 = new Point2D(x1,y1);
p2 = new Point2D(x2,y2);
}

/**
* Return a string describing the 3D point
*/
public String toString() {
return "(" + p1.x + ", " + p1.y + "), (" + +p2.x + ", " + p2.y + ")";
}

/**
* Override the default hashcode method
*/
// TODO: write hashCode method
public int hashCode() {
int hash = 17;
hash = hash * 31 + p1.hashCode();
hash = hash * 31 + p2.hashCode();
return hash;
}

/**
* Override the default equals method.
* Two BoxRegion objects equal if the coordinates
* of their opposing points are equal.
*/
// TODO: Write equals method
public boolean equals(Object obj) {
if (obj instanceof Point2D == false){
return false;
}
BoxRegion b = (BoxRegion) obj;
if ( p1!= b.p1 || p2 != b.p2) {
return false;
}
return true;
}
}

--------------------------------------Point2D.java--------------------------------------

/**
* Object for storing a 2D point.
*
* @author rlsummerscales
*
**/
public class Point2D {
final int x;
final int y;
  
/** Create a new 2D point with given x and y values
*
* @param xValue is the value for the x-coordinate
* @param yValue is the value for the y-coordinate
*/
public Point2D(int xValue, int yValue) {
x = xValue;
y = yValue;
}
  
/** Return a string describing the 2D point */
public String toString() {
return "(" + x + ", " + y + ")";
}
  
  
/** Override the default hashcode method */
public int hashCode() {
int hash = 13;
hash = 31*hash + ((Integer) x).hashCode();
hash = 31*hash + ((Integer) y).hashCode();
return hash;
}
  
/** Override the default equals method.
* Two Point2D objects equal if their values are equal.
*/
public boolean equals(Object obj) {
if (obj instanceof Point2D == false){
return false;
}
Point2D p = (Point2D) obj;
if (x != p.x || y != p.y) {
return false;
}
return true;
}
  
}

--------------------------------------BoxRegionHashTable.java--------------------------------------

import java.util.*;

public class BoxRegionHashTable {
/** Output the annotation for a given BoxRegion
*
* @param key is the BoxRegion
* @param annotationMap is a map of annotation string for a set of points
**/

// TODO: Write function displayAnnotation.
public static void displayAnnotation(BoxRegion b, HashMap<Integer, String> annotationMap){
if(annotationMap.containsKey(b.hashCode())){
System.out.println("Annotation: " + annotationMap.get(b.hashCode()));
}else{
System.out.println("It has no annotation");
}
}

// It should output the annotation for a given key for a given HashMap.
// if point is not in hash table, display message stating that it has no annotation

  
/** Test the equals and hashCode implementations in BoxRegion
* @param args is an array of command line arguments
**/
public static void main(String[] args) {
// TODO: Create hash map of BoxRegion objects with their annotations as keys
HashMap<Integer, String> annotationMap = new HashMap<Integer, String>();
// TODO: Insert BoxRegions and corresponding strings into table
annotationMap.put((new BoxRegion(45, 237, 60, 300)).hashCode(), "Box1");
// the following should be successful
displayAnnotation(new BoxRegion(45, 237, 60, 300), annotationMap);
displayAnnotation(new BoxRegion(1175, 140, 350, 418), annotationMap);
displayAnnotation(new BoxRegion(2000, 0, 1700, 3000), annotationMap);
displayAnnotation(new BoxRegion(1460, 1030, 819, 1420), annotationMap);
  
// the following should fail
displayAnnotation(new BoxRegion(237, 45, 300, 60), annotationMap);
displayAnnotation(new BoxRegion(0, 0, 0, 0), annotationMap);
}
  
}