public class WordPair { 
    /** Constructs a WordPair object. */ 
    public WordPair(String first, String second) 
    { 
        /* implementation not shown */ 
    } 
    /** Returns the first string of this WordPair object. */ 
    public String getFirst() 
    { 
        /* implementation not shown */ 
    } /** Returns the second string of this WordPair object. */ 
    public String getSecond() 
    {
        /* implementation not shown */ 
    } 
}
public class WordPairList { 
    /** The list of word pairs, initialized by the constructor. */ 
    private ArrayList<WordPair> allPairs; 
    /** Constructs a WordPairList object as described in part (a). * Precondition: words.length >= 2 */ 
    public WordPairList(String[] words) 
    { 
        /* to be implemented in part (a) */ 
    } 
    /** Returns the number of matches as described in part (b). */ 
    public int numMatches() { 
        /* to be implemented in part (b) */
    } 
}

public class WordPair {
    private String First;
    private String Second;
    /** Constructs a WordPair object. */ 
    public WordPair(String first, String second) 
    { 
        this.First = first;
        this.Second = second;
    } 
    /** Returns the first string of this WordPair object. */ 
    public String getFirst() 
    { 
        return this.First;
    } /** Returns the second string of this WordPair object. */ 
    public String getSecond() 
    {
        return this.Second;
    } 
}
public class WordPairList { 
    /** The list of word pairs, initialized by the constructor. */ 
    private ArrayList<WordPair> allPairs; 
    /** Constructs a WordPairList object as described in part (a). * Precondition: words.length >= 2 */ 
    public WordPairList(String[] words) 
    { 
        this.allPairs = new ArrayList<WordPair>(); //Some people miss this for some reason. You need an array list so that way you can add more pairs needed in the future.
        for (int i = 0; i<words.length;i++){ //Goes through each word
            for(int j = i+1;j<words.length;j++){ //This is the nested for loop; The i+1 makes it so that j doesn't overlap itself, otherwise, it would think that it was pairing with itself; Many people miss this surprisingly
                this.allPairs.add(new WordPair(words[i],words[j]));
            }
        }
    } 
    /** Returns the number of matches as described in part (b). */ 
    public int numMatches() { 
        int result = 0;
        for (WordPair wp:allPairs){ //this for iterates through each word pair in the allPairs arraylist
            if(wp.getFirst() == wp.getSecond()){ //This makes sure that the words are equal to each other to create a valid pair.
                result += 1; //This increments for every pair
            }
        }
        return result;
    } 
}

//Main Function
//Example 1:
String[] wordNums = {"one", "two", "three"}; 
WordPairList exampleOne = new WordPairList(wordNums);
//Example 2
String[] phrase = {"the", "more", "the", "merrier"}; 
WordPairList exampleTwo = new WordPairList(phrase);
//Example 3:
String[] moreWords = {"the", "red", "fox", "the", "red"}; 
WordPairList exampleThree = new WordPairList(moreWords);
System.out.println("Here are the results for example 2 and 3");
System.out.println(exampleOne.numMatches());
System.out.println(exampleTwo.numMatches());
System.out.println(exampleThree.numMatches());

Here are the results for example 2 and 3
0
1
2

Overloaded Constructor

Below is an example of an overloaded constructor. It’s identical to the code above, except now when creating a WordPairList object if we don’t pass through any words, tester words will be given and used.

public class WordPairList { 
    /** The list of word pairs, initialized by the constructor. */ 
    private ArrayList<WordPair> allPairs; 
    /** Constructs a WordPairList object as described in part (a). * Precondition: words.length >= 2 */ 
    public WordPairList(String[] words) 
    { 
        this.allPairs = new ArrayList<WordPair>(); 
        for (int i = 0; i<words.length;i++){ 
            for(int j = i+1;j<words.length;j++){ 
                this.allPairs.add(new WordPair(words[i],words[j]));
            }
        }
    } 

    public WordPairList() 
    { 
        String[] testerWords = {"test", "testing", "best", "test", "hello"}; 
        this.allPairs = new ArrayList<WordPair>(); 
        for (int i = 0; i<testerWords.length;i++){ 
            for(int j = i+1;j<testerWords.length;j++){ 
                this.allPairs.add(new WordPair(testerWords[i],testerWords[j]));
            }
        }
    } 

    /** Returns the number of matches as described in part (b). */ 
    public int numMatches() { 
        int result = 0;
        for (WordPair wp:allPairs){ //this for iterates through each word pair in the allPairs arraylist
            if(wp.getFirst() == wp.getSecond()){ //This makes sure that the words are equal to each other to create a valid pair.
                result += 1; //This increments for every pair
            }
        }
        return result;
    } 
}

String[] words = {"the", "more", "the", "merrier"}; 
WordPairList exampleOne = new WordPairList(words);
WordPairList exampleTwo = new WordPairList();
System.out.println("Here are the results for the examples");
System.out.println(exampleOne.numMatches());
System.out.println(exampleTwo.numMatches());

Here are the results for the examples
1
1

Resources

GridWorld Case Study is a program that was previously used to supplement the AP CSA curriculum and was on the AP Exam from 2008 to 2014. While it is no longer tested, it is still a useful program to help prepare for the AP Exam as it provides a graphical environment that shows objects inhabiting and interacting with each other in a grid. For those interested, you can start here.

Tips and Tricks

Hacks:

Complete this FRQ AND write about a possible application in 3 sentences AND create an example of a real life application with that FRQ.

Prompt

You are tasked with implementing a simple online shopping system. The system consists of classes to represent products, customers, and orders. Your task is to complete the missing methods and implement additional functionality as described in the comments.

public class Product {
    private String name;
    private double price;

    // TODO: Implement the Product class
}

// Customer.java
public class Customer {
    private String name;
    private String email;
    private String address;

    // TODO: Implement the Customer class
}

// Order.java
import java.util.ArrayList;

public class Order {
    private Customer customer;
    private ArrayList<Product> products;

    // TODO: Implement the Order class
}

Your Task:

Complete the implementations of the Product, Customer, and Order classes according to the following specifications:

Additional Requirements:

Ensure that prices are non-negative and orders cannot be created without a customer. Implement proper error handling and validation for invalid operations or inputs. Document your code with clear comments to explain the purpose and functionality of each method. Demonstrate the usage of your implementations with sample test cases in a separate class.

Note:

This question assesses your understanding of class design, constructors, methods, encapsulation, and error handling. Take your time to carefully analyze the requirements and design your solutions accordingly. Soley using AI for any part of the hack results in a 0 for the whole thing.

Instantiation of Classes