- (25%) What does the following program print out when run?
public class Q1 {
public static boolean swing (int strength) throws Exception{public static void main(String[] args) {
if (strength < 5)
throw new Exception("Too weak");
if (strength > 10)
return false;
return true;
}
int[] strengths = {5,6,-1,12};
for (int s : strengths) {
try {
if (swing(s))
System.out.println("Homerun");
else
System.out.println("Strike!");
} catch (RuntimeException e){
System.out.println("You are OUT!");
} catch (Exception e) {
System.out.println(e.getMessage());
}
}
System.out.println("Done.");
}
}
- (25%)Given a text file called sales.txt which contains data that looks like
aba 55.99 akdkd8dj 12.95 iwjwhe 4 Iji8keJl 44.99 ijdddawe 10.00 ...and so on for many more rows...
where each row represents one item that is for sale in a store. The first column is a String that uniquely identifies the item and the second column is a double that represents the price of the item. Write a program which
- Implements a simple
Itemclass that can represent one item. - In the
main, your program reads the complete contents of the file sales.txt into anArrayList<Item>variable calleditems.
Answer:
public class Item {
private String sku;
private double price;
public Item(String sku, double price){
this.sku = sku;
this.price = price;
}
public String toString(){
return sku + " " + price;
}
public static void main(String[] args) {
try {
Scanner in = new Scanner(new FileInputStream("sales.txt"));
ArrayList<Item> items = new ArrayList<Item>();
while (in.hasNext()){
String sku = in.next();
double price = in.nextDouble();
items.add(new Item(sku,price));
}
System.out.println(items);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
} - Implements a simple
- (25%) Read over the code below and implement the empty method.
import java.util.ArrayList;
For example, when the main above is run it should print out
public class Q3 {
private ArrayList<Q3> data;
private Integer number;
public Q3(Integer number){
data = new ArrayList<Q3>();
this.number = number;
}
public void add(Q3 q){
data.add(q);
}
public void add(Integer number){
data.add(new Q3(number));
}
/**
* Calculates and returns the sum of all even numbers in
* this object or in any of the ones in 'data', and so on
* recursively.
* @return The sum.
*/
public int sumEven(){
//TODO: implement this method
int result = 0;
if (number % 2 == 0)
result = number;
for (Q3 q: data){
result += q.sumEven();
}
return result;
}
public static void main(String[] args) {
Q3 q = new Q3(0);
Q3 first = new Q3(1);
q.add(first);
Q3 second = new Q3(2);
q.add(second);
q.add(3);
q.add(4);
first.add(8);
second.add(5);
System.out.println(q.sumEven());
}
}14
- (25%) Implement a method
String mostFrequent(String s)which returns the 3-character substring that appears most frequently ins, or one of the most frequent if there is a tie. For examplemostFrequent("AABABA") returns "ABA" because "ABA" appears twice mostFrequent("AAAAAB") returns "AAA" because it appears 3 times mostFrequent("ATATATA") returns "ATA" because it appears 3 timesAnswer:public static String mostFrequent(String seq){
HashMap<String, Integer> count = new HashMap<String, Integer>();
int max = 0;
String maxKey = null;
//add them all
for (int i = 0; i <= seq.length() - 3; i++) {
String key = seq.substring(i,i+3);
if (count.containsKey(key))
count.put(key, count.get(key) + 1);
else
count.put(key, 1);
if (count.get(key) > max){
max = count.get(key);
maxKey = key;
}
}
return maxKey;
}
And, the other one:
- (25%) What does the following program print out when run?
public class Q1 {
public static boolean pitch (String type) throws Exception {public static void main(String[] args) {
if (type.startsWith("f"))
return true;
if (type.startsWith("c"))
return false;
if (type.startsWith("x"))
throw new Exception("Oops");
return true;
}
String[] types = {"fast", "foo", "curve", "xoom"};
for (String t : types) {
try {
if (pitch(t))
System.out.println("Hit");
else
System.out.println("Miss");
} catch (RuntimeException e){
System.out.println("You hit the umpire");
}
catch (Exception e) {
System.out.println(e.getMessage());
}
}
System.out.println("Done.");
}
}
- (25%) Given a text file called points.txt which contains data that looks like
1.44 5.666 12.999 0 9.163 3.1415 6 7 5 6.999 ...and so on for many more rows...
where each row represents the x and y coordinates of a point in 2-dimensional space. Both columns are doubles. Write a program which
- Implements a simple
Pointclass that can represent one point in space. - In the
main, your program reads the complete contents of the file points.txt into anArrayList<Point>variable calledpoints.
Answer:
public class Point {
private double x;
private double y;
public Point(double x, double y){
this.x = x;
this.y = y;
}
public String toString(){
return "(" + x + "," + y + ")";
}
public static void main(String[] args) {
try {
Scanner in = new Scanner(new FileInputStream("points.txt"));
ArrayList<Point> points = new ArrayList<Point>();
while (in.hasNext()){
double x= in.nextDouble();
double y = in.nextDouble();
points.add(new Point(x,y));
}
System.out.println(points);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
} - Implements a simple
- (25%) Read over the code below and implement the empty method.
import java.util.ArrayList;
For example, when the main above is run it should print
public class Q3 {
private ArrayList<Q3> data;
private Integer number;
public Q3(Integer number){
data = new ArrayList<Q3>();
this.number = number;
}
public void add(Q3 q){
data.add(q);
}
public void add(Integer number){
data.add(new Q3(number));
}
/**
* Find if x is either equal to number, or equal to one of
* the numbers in 'data', and so on recursively.
* @param x the number we are looking for
* @return true if x is there, false otherwise.
*/
public boolean find(Integer x){
//TODO: implement this method
if (number == x)
return true;
for (Q3 q : data) {
if (q.find(x))
return true;
}
return false;
}
public static void main(String[] args) {
Q3 q = new Q3(0);
Q3 first = new Q3(1);
q.add(first);
Q3 second = new Q3(2);
q.add(second);
q.add(3);
q.add(4);
first.add(8);
second.add(5);
System.out.println(q.find(3));
System.out.println(q.find(5));
System.out.println(q.find(10));
}
}
outtrue true false
- (25%) Implement a method
String mostPoints(String[] name, int[] points)which returns the name that has the most points, assuming that for all indecesiwe have thatpoints[i]has the number of points forname[i]. For exampleString[] name1 = {"a", "b", "c", "a", "b", "a"};
int[] points1 = { 1, 2, 7, 4 , 3, 1};
mostPoints(name1, points1); //returns "c" because it has 7
// points and "a" has 6, and "b" has 5.
String[] name2 = {"a", "b", "c", "a", "b", "a"};
int[] points2 = { 5, 2, 7, 4 , 3, 1};
mostPoints(name2, points2); //returns "a"
String[] name3 = {"a", "a", "a", "a", "b", "c"};
int[] points3 = { 1, 1, 1, 1 , 3, 2};
mostPoints(name3, points3); //returns "a"Answer:public static String mostPoints(String[] name, int[] points){
HashMap<String, Integer> count = new HashMap<String, Integer>();
int max = 0;
String maxKey = null;
for (int i = 0; i < points.length; i++) {
if (count.containsKey(name[i]))
count.put(name[i], points[i] + count.get(name[i]));
else
count.put(name[i], points[i]);
if (count.get(name[i]) > max){
max = count.get(name[i]);
maxKey = name[i];
}
}
return maxKey;
}
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