Use Loops, Conditionals, and HashMaps package code; import java.util.HashMap; pu
ID: 3588966 • Letter: U
Question
Use Loops, Conditionals, and HashMaps
package code;
import java.util.HashMap;
public class Model {
public class Model {
/*
* DESCRIBING A PLACE
*
* Given:
* a String, the name of place,
* a HashMap<String,Point2D> containing a place name to location mapping, and
* a HashMap<String,Integer> containing a place name to population mapping,
* return a String that describes that place as in the example below.
*
* You may assume that if there is an entry for String in either of the two HashMaps, then
* there is an entry for that String in both.
*
* If there is no entry for the String in either HashMap, return the string
* "Requested place is unknown: <placename>."
* where <placename> is replaced by the requested place name.
*
* Suppose we know the following about Tonawanda City:
*
* Tonawanda City is at 43.020335,-78.880315, according to http://www.itouchmap.com/latlong.html
* The population of Tonawanda City is 15,130 (https://en.wikipedia.org/wiki/Tonawanda_(city),_New_York)
*
* Assuming that "Tonawanda City" has an entry in both HashMaps, reflecting this information, the String
* returned must be:
*
* "Tonawanda City has latitude 43.020335, longitude -78.880315, and has a population of 15130 persons."
*
* For example, assuming that "Omicron Persei 8" does not exist in either HashMap, the String
* returned must be:
*
* "Requested place is unknown: Omicron Persei 8."
*/
public String description(String name, HashMap<String,Point2D> location, HashMap<String, Integer> population) {
String answer = "";
return answer;
}
/*
* FIND THE CLOSEST PLACE
*
* Given:
* a Point2D, representing a location, and
* a HashMap<String,Point2D>, containing a place name to location mapping,
* return a String that gives the place name of the closest place to that location from the HashMap.
*
* You may assume that the HashMap has at least one entry - this means that there is
* in fact a closest place!
*
* HINT: Use a figure larger than the Earth's equatorial circumference to seed the closest distance.
* https://www.space.com/17638-how-big-is-earth.html
*
* HINT: Remember that you can obtain the set of keys for which the HashMap has entries by calling
* the keySet() method on the HashMap.
*
* HINT: Keep track of both the shortest distance you've come across so far and the name of that place
* as you iterate through the loop.
*/
public String closestToPoint(Point2D p, HashMap<String, Point2D> location) {
String closest = "";
return closest;
}
Explanation / Answer
1.
public String description(String name, HashMap < String, Point2D > location, HashMap < String, Integer > population) {
String answer = "";
Point2D loc = location.get(name);
if (loc == null) {
answer += "Requested place is unknown :" + name;
return answer;
} else {
answer += name + " has latitude" + loc.getLatitude + ", longitude " + loc.getLongitude + ",";
}
Integer pop = population.get(name);
if (pop == null) {
answer += "The area has no population";
} else {
answer += "and has a population of" + pop + " persons."
}
return answer;
}
2.
public String closestToPoint(Point2D p, HashMap < String, Point2D > location) {
String closest = "";
Float distance = Integer.MAX;
for (String n: location.keySet()) {
Point2D m = location.get(n);
float d = getnearest(p, m);
if(d < distance){
distance =d;
closest = name;
}
}
return closest;
}
public float getnearest(Point2D p, Point2D m) {
float R = radius; //Radius of earth
float 1 = p.latitude.toRadians();
float 1 = p.longitude.toRadians();
float 2 = m.latitude.toRadians();
float 2 = m.longitude.toRadians();
var = 2 - 1;
var = 2 - 1;
var a = Math.sin( / 2) * Math.sin( / 2) + Math.cos(1) * Math.cos(2) * Math.sin( / 2) * Math.sin( / 2);
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
var d = R * c;
return d;
}
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