Contents
- ./FindDuplicates.java
- ./TestShortcuts.java
- ./PetSurvey3.java
- ./PlanetTest.java
- ./Fruit.java
./FindDuplicates.java 1/5
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package examples;
import java.util.HashSet;
import java.util.Set;
/**
* From the array of command-line arguments, identify the duplicates
*
* @author CS209
*
*/
public class FindDuplicates {
/**
*
* @param args
*/
public static void main(String args[]) {
Set<String> argSet = new HashSet<String>();
for(int i=0; i < args.length; i++ ) {
// try to add argument to set
if( ! argSet.add(args[i]) ) {
System.out.println("Duplicate: " + args[i]);
}
}
System.out.println(argSet.size() + " unique words: " + argSet);
}
}
./TestShortcuts.java 2/5
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package examples;
/**
* Demonstrate use of shortcuts
*
* Pre-operator (i.e., ++i or --i): operation is performed and value is produced
* Post-operator (i.e., i++ or i--), value is produced, then operation is performed
*
* @author sprenkle
*
*/
public class TestShortcuts {
public static void main(String[] args) {
int i = 1;
System.out.println("i : " + i); // Output: 1
System.out.println("++i : " + ++i); // Pre-increment: 2
System.out.println("i++ : " + i++); // Post-increment: 2
System.out.println("i : " + i); // 3
System.out.println("--i : " + --i); // Pre-decrement: 2
System.out.println("i-- : " + i--); // Post-decrement: 2
System.out.println("i : " + i); // 1
}
}
./PetSurvey3.java 3/5
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package examples;
import java.io.*;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
import java.util.Set;
/**
* This class represents a pet survey, keeping track of the number of votes cast
* for a set of pets. The results are stored in a file.
*
* Modified to use a collection.
*
* @author CS209
*
*/
public class PetSurvey3 {
private String filename;
private int totalVotes = 0;
Map<String, Integer> petToVotes;
public PetSurvey3(String fn) {
this.filename = fn;
petToVotes = new HashMap<String, Integer>();
importResults();
}
/**
* Read the survey data from the file
*/
private void importResults() {
try {
BufferedReader input = new BufferedReader(new FileReader(filename));
String line;
int i = 0;
while ((line = input.readLine()) != null) {
// line format: <animal> <numVotes>
String data[] = line.split(" ");
String animal = data[0];
int numVotes = Integer.parseInt(data[1]);
petToVotes.put(animal, numVotes);
i++;
totalVotes += numVotes;
}
input.close();
} catch (FileNotFoundException e) {
System.out.println(filename
+ ", containing the survey results, not found");
e.printStackTrace();
} catch (IOException e) {
System.out
.println("Something went wrong while importing survey results from"
+ filename);
e.printStackTrace();
}
}
/**
* Store the current voting results into the file
*/
public void storeResults() {
try {
PrintWriter writer = new PrintWriter(filename);
Set<String> keys = petToVotes.keySet();
for (String animal: keys) {
writer.println(animal + " " + petToVotes.get(animal));
}
writer.close();
} catch (IOException e) {
System.out.println("Error storing survey results to file "
+ filename);
e.printStackTrace();
}
}
/**
*
* @return the name of the file containing the survey results
*/
public String getFilename() {
return filename;
}
/**
*
* @return the array of Strings of animal names in the survey
*/
public String[] getAnimals() {
Set<String> animals = petToVotes.keySet();
String[] animalsArray = (String[]) animals.toArray();
return animalsArray;
}
/**
*
* @return the number of votes that have been cast.
*/
public int getTotalVotes() {
return totalVotes;
}
/**
* Casts a vote for the animal
*
* @param animal
*/
public void castVote(String animal) {
Integer numVotes = petToVotes.get(animal);
if( numVotes == null ) {
petToVotes.put(animal, 1);
} else {
petToVotes.put(animal, numVotes+1);
}
totalVotes++;
}
/**
* Display the results from the survey in a nicely formatted way.
*/
public void displayResults() {
System.out.printf("%-10s%7s%13s\n", "Animal", "Votes", "Percentage");
System.out.println("------------------------------");
Set<String> keys = petToVotes.keySet();
for( String animal : keys ) {
int votes = petToVotes.get(animal);
double pct = (double) votes/totalVotes * 100;
System.out.printf("%-10s%7d%12.2f%%\n", animal, votes, pct);
}
System.out.println("Total votes cast: " + totalVotes);
}
/**
* @param args
* not used in this program.
*/
public static void main(String[] args) {
final String mySurveyFile = "petSurvey.dat";
PetSurvey3 survey = new PetSurvey3(mySurveyFile);
System.out.println("Current Results: ");
survey.displayResults();
// Allow User to Vote
Scanner scanner = new Scanner(System.in);
System.out
.print("What animal do you want to vote for as your favorite? (dog, cat, bird, snake, fish, other): ");
String animalVoted = scanner.nextLine();
scanner.close();
survey.castVote(animalVoted);
// Display updated results
System.out.println("Updated Results: ");
survey.displayResults();
survey.storeResults();
}
}
./PlanetTest.java 4/5
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package examples;
/**
* Example demonstrates a more sophisticated enumerated type.
*
*/
public class PlanetTest {
public enum Planet {
MERCURY(3.302e+23, 2.439e6),
VENUS(4.869e+24, 6.0518e6),
EARTH(5.976e+24, 6.37814e6),
MARS(6.421e+23, 3.3972e6),
JUPITER(1.9e+27, 7.1492e7),
SATURN(5.688e+26, 6.0268e7),
URANUS(8.686e+25, 2.5559e7),
NEPTUNE(1.024e+26, 2.4746e7);
private final double mass;
private final double radius;
private final double surfaceGravity;
private static final double G = 6.67300E-11;
// Note: Package-private; Can't be more visible than package-private
Planet(double mass, double radius) {
this.mass = mass;
this.radius = radius;
surfaceGravity = G * mass / (radius * radius);
}
public double mass() {
return mass;
}
public double radius() {
return radius;
}
public double surfaceGravity() {
return surfaceGravity;
}
public double surfaceWeight(double mass) {
return mass * surfaceGravity; // F = ma
}
}
/**
* @param args
*/
public static void main(String[] args) {
double earthWeight = 150;
double mass = earthWeight/Planet.EARTH.surfaceGravity();
for (Planet p : Planet.values())
System.out.printf("Your weight on %s is %10.4f%n",
p, p.surfaceWeight(mass));
}
}
./Fruit.java 5/5
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/**
*
*/
package examples;
/**
* @author sprenkle
*
*/
public class Fruit {
public enum Apple {FUJI, PIPPIN, GRANNY_SMITH};
public enum Orange {NAVEL, TEMPLE, BLOOD};
/**
* @param args
*/
public static void main(String[] args) {
}
}
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