Question

JAVA programming

9.9 Ch 9, Part 2: ArrayList Searching

import java.util.ArrayList;

public class ArrayListSet {

    /**
     * Searches through the ArrayList arr, from the first index to the last, returning an ArrayList
     * containing all the indexes of Strings in arr that match String s. For this method, two Strings,
     * p and q, match when p.equals(q) returns true or if both of the compared references are null.
     *
     * @param s The string to search for.
     * @param arr The ArrayList of string to search.
     * @return An ArrayList of the indexes in arr that match s. The ArrayList will be ordered from
     *         the smallest index to the largest. If arr is null, the method will return null.
     */
    public static ArrayList<Integer> findExact(String s, ArrayList<String> arr) {
        return null;
    }

    /**
     * Searches through the ArrayList arr, from the first index to the last, returning an ArrayList
     * containing all the indexes of Strings in arr that contains String s. For this method, a
     * Strings p contains q when p.contains(q) returns true or if both of the compared references are null.
     *
     * @param s The string to search for.
     * @param arr The ArrayList of string to search.
     * @return An ArrayList of the indexes in arr that contains s. The ArrayList will be ordered from
     *         the smallest index to the largest. If arr is null, the method will return null.
     */
    public static ArrayList<Integer> findContains(String s, ArrayList<String> arr) {
        return null;
    }

    /**
     * Adds String s to the end of the ArrayList arr if and only if arr does not already have an
     * element that matches s.
     *
     * Do not duplicate code! Use your findExact method to check if arr contains s.
     *
     * @param s The string to add (if not already in arr).
     * @param arr The ArrayList in which to s (if a String with the same contents is not already in
     *            arr).
     * @return The number of times that s is found in arr after attempting to adding s. If arr is null,
     *         return -1.
     */
    public static int addUniqueString(String s, ArrayList<String> arr) {
        return -42;
    }

}

import java.util.ArrayList;
import java.util.Arrays;

public class TestArrayListSet {

    public static boolean testFindExact() {
        System.out.println("Starting testFindExact...");
        //Test 1
        {
            ArrayList<Integer> ret =
                ArrayListSet.findExact("foo", new ArrayList<String>(Arrays.asList("foo","bar","foo")));
            ArrayList<Integer> exp = new ArrayList<Integer>(Arrays.asList(0, 2));
            if(!ret.equals(exp)) {
                System.out.println("Test 1 failed!");
                System.out.println("Returned: " + ret);
                System.out.println("Expected: " + exp);
                return false;
            }
        }
        System.out.println("...Done testFindExact");
        return true;
    }

    public static boolean testFindContains() {
        System.out.println("Starting testFindContains...");
        //Test 1
        {
            ArrayList<Integer> ret =
                ArrayListSet.findContains("o", new ArrayList<String>(Arrays.asList("foo","bar","foo")));
            ArrayList<Integer> exp = new ArrayList<Integer>(Arrays.asList(0, 2));
            if(!ret.equals(exp)) {
                System.out.println("Test 1 failed!");
                System.out.println("Returned: " + ret);
                System.out.println("Expected: " + exp);
                return false;
            }
        }
        System.out.println("...Done testFindContains");
        return true;
    }

    public static boolean testAddUniqueString() {
        System.out.println("Starting testAddUniqueString...");
        //Test 1
        {
            ArrayList<String> arr = new ArrayList<String>(Arrays.asList("a","b","c"));
            ArrayList<String> exp = new ArrayList<String>(arr);
            exp.add("d");
            int retIndex = ArrayListSet.addUniqueString("d", arr);
            int expIndex = 1;
            if(!arr.equals(exp) || retIndex != expIndex) {
                System.out.println("Test 1 failed!");
                System.out.println("Returned value: " + retIndex + "; expected " + expIndex);
                System.out.println("List after: " + arr);
                System.out.println("Expected: " + exp);
                return false;
            }
        }
        //Test 2
        {
            ArrayList<String> arr = new ArrayList<String>(Arrays.asList("a","b","b","c"));
            ArrayList<String> exp = new ArrayList<String>(arr);
            int retIndex = ArrayListSet.addUniqueString("b", arr);
            int expIndex = 2;
            if(!arr.equals(exp) || retIndex != expIndex) {
                System.out.println("Test 2 failed!");
                System.out.println("Returned value: " + retIndex + "; expected " + expIndex);
                System.out.println("List after: " + arr);
                System.out.println("Expected: " + exp);
                return false;
            }
        }
        System.out.println("...Done testAddUniqueString");
        return true;
    }
  
    public static void main(String[] args) {
        testFindExact();
        testFindContains();
        testAddUniqueString();
    }
  
}

Answer 1

Given below is the code for the question. Run the TestArrayListSet.java provided by instructor.
Please do rate the answer if it helped. Thank you.

import java.util.ArrayList;

public class ArrayListSet {

/**
* Searches through the ArrayList arr, from the first index to the last, returning an ArrayList
* containing all the indexes of Strings in arr that match String s. For this method, two Strings,
* p and q, match when p.equals(q) returns true or if both of the compared references are null.
*
* @param s The string to search for.
* @param arr The ArrayList of string to search.
* @return An ArrayList of the indexes in arr that match s. The ArrayList will be ordered from
* the smallest index to the largest. If arr is null, the method will return null.
*/
public static ArrayList<Integer> findExact(String s, ArrayList<String> arr) {
   if(arr == null)
       return null;
   ArrayList<Integer> indices = new ArrayList<Integer>();
   for(int i = 0; i < arr.size(); i++) {
       if((s == null && arr.get(i) == null) || s.equals(arr.get(i)))
           indices.add(i);
   }
return indices;
}

/**
* Searches through the ArrayList arr, from the first index to the last, returning an ArrayList
* containing all the indexes of Strings in arr that contains String s. For this method, a
* Strings p contains q when p.contains(q) returns true or if both of the compared references are null.
*
* @param s The string to search for.
* @param arr The ArrayList of string to search.
* @return An ArrayList of the indexes in arr that contains s. The ArrayList will be ordered from
* the smallest index to the largest. If arr is null, the method will return null.
*/
public static ArrayList<Integer> findContains(String s, ArrayList<String> arr) {
   if(arr == null)
       return null;
  
   ArrayList<Integer> indices = new ArrayList<Integer>();
   for(int i = 0; i < arr.size(); i++) {
       if((arr.get(i) == null && s == null) || (arr.get(i) != null && arr.get(i).contains(s)) )
           indices.add(i);
   }
return indices;
}

/**
* Adds String s to the end of the ArrayList arr if and only if arr does not already have an
* element that matches s.
*
* Do not duplicate code! Use your findExact method to check if arr contains s.
*
* @param s The string to add (if not already in arr).
* @param arr The ArrayList in which to s (if a String with the same contents is not already in
* arr).
* @return The number of times that s is found in arr after attempting to adding s. If arr is null,
* return -1.
*/
public static int addUniqueString(String s, ArrayList<String> arr) {
   ArrayList<Integer> idx = findExact(s, arr);
   if(idx == null)
       return -1;
   if(idx.isEmpty())
   {
       arr.add(s);
       return 1;
   }
   else
       return idx.size();
}

}

output
---
Starting testFindExact...
...Done testFindExact
Starting testFindContains...
...Done testFindContains
Starting testAddUniqueString...
...Done testAddUniqueString