StringArrayUtils.java

package com.zipcodewilmington;

import java.util.*;

/**
 * Created by leon on 1/29/18.
 */
public class StringArrayUtils {
    /**
     * @param array array of String objects
     * @return first element of specified array
     */ // TODO
    public static String getFirstElement(String[] array) {
        return array[0];
    }

    /**
     * @param array array of String objects
     * @return second element in specified array
     */
    public static String getSecondElement(String[] array) {
        return array[1];
    }

    /**
     * @param array array of String objects
     * @return last element in specified array
     */ // TODO
    public static String getLastElement(String[] array) {
        return array[array.length - 1];
    }

    /**
     * @param array array of String objects
     * @return second to last element in specified array
     */ // TODO
    public static String getSecondToLastElement(String[] array) {
        return array[array.length - 2];
    }

    /**
     * @param array array of String objects
     * @param value value to check array for
     * @return true if the array contains the specified `value`
     */ // TODO
    public static boolean contains(String[] array, String value) {
        List<String> arrayList = new ArrayList<>(Arrays.asList(array));
        return arrayList.contains(value);
    }

    /**
     * @param array of String objects
     * @return an array with identical contents in reverse order
     */ // TODO
    public static String[] reverse(String[] array) {
        String[] reversedArray = new String[array.length];
        int j = array.length - 1;
        for(int i = 0; i < array.length; i++){
            reversedArray[j--] = array[i];
        }
        return reversedArray;
    }

    /**
     * @param array array of String objects
     * @return true if the order of the array is the same backwards and forwards
     */ // TODO
    public static boolean isPalindromic(String[] array) {
        int midPoint = array.length / 2;
        int lastIndex = array.length - 1;
        for(int i = 0; i < midPoint; i++){
            if(!array[i].equals(array[lastIndex - i])) return false;
        }
        return true;
    }

    /**
     * @param array array of String objects
     * @return true if each letter in the alphabet has been used in the array
     */ // TODO
    public static boolean isPangramic(String[] array) {
        String alphabet = "abcdefghijklmnopqrstuvwxyz";
        List<String> arrayList = new ArrayList<>(Arrays.asList(array));
        String allContents = arrayList.toString();
        allContents = allContents.replaceAll(",", "").replaceAll(" ", "").toLowerCase(Locale.ROOT);
        for(int i = 0; i < alphabet.length(); i++){
            if(allContents.indexOf(alphabet.charAt(i)) == -1) return false;
        }
        return true;
    }

    /**
     * @param array array of String objects
     * @param value value to check array for
     * @return number of occurrences the specified `value` has occurred
     */ // TODO
    public static int getNumberOfOccurrences(String[] array, String value) {
        int count = 0;
        for(String element : array){
            if(element == value){
                count++;
            }
        }
        return count;
    }

    /**
     * @param array         array of String objects
     * @param valueToRemove value to remove from array
     * @return array with identical contents excluding values of `value`
     */ // TODO
    public static String[] removeValue(String[] array, String valueToRemove) {
        ArrayList<String> arrayList = new ArrayList<>();
        Collections.addAll(arrayList, array);
        while(arrayList.contains(valueToRemove)){
            arrayList.remove(valueToRemove);
        }
        return arrayList.toArray(new String[0]);
    }

    /**
     * @param array array of chars
     * @return array of Strings with consecutive duplicates removes
     */ // TODO
    public static String[] removeConsecutiveDuplicates(String[] array) {
        ArrayList<String> arrayList = new ArrayList<>();
        String lastElement = "";
        for(String element : array){
            if(element != lastElement){
                arrayList.add(element);
            }
            lastElement = element;
        }
        return arrayList.toArray(new String[0]);
    }

    /**
     * @param array array of chars
     * @return array of Strings with each consecutive duplicate occurrence concatenated as a single string in an array of Strings
     */ // TODO

    /*
     String[] array = {"a", "a", "a", "b", "c", "c", "a", "a", "d"}; arrayList has 1 position, and it's an a.
     String[] expected = {"aaa", "b", "cc", "aa", "d"};

     */
    public static String[] packConsecutiveDuplicates(String[] array) {
        int length = array.length;
        int lastIndex = 0;
        ArrayList<String> arrayList = new ArrayList<>();
        arrayList.add(array[0]);

        for(int i = 1; i < length; i++){
            if(arrayList.get(lastIndex).contains(array[i])){ //does my arrayList, at the last examined index contain what the array current shows
                arrayList.set(lastIndex, (arrayList.get(lastIndex) + array[i])); //arrayList.set(index, value)
            } else { //no longer looking at a consecutive
                lastIndex++; //I'm looking at a new 0R non-duplicate character
                arrayList.add(array[i]);
            }
        }
        return arrayList.toArray(new String[0]);
    }


}