sample.java

import java.util.Arrays;

public class ArrayMethods
{
    String[] list; //instance variable
    /**
     * Constructor for objects of class ArrayMethods
     */
    public ArrayMethods(String[] list)
    {
        // initialise instance variables
        this.list = list;
    }

    /**
     * Determines if the array is sorted (do not sort)
     * When Strings are sorted, they are in alphabetical order
     * Use the compareTo method to determine which string comes first
     * You can look at the String compareTo method in the Java API
     * @return true if the array  is sorted, else false.
     */
    public boolean isSorted()
    {
        boolean sorted = true;

        // TODO: Write the code to loop through the array and determine that each
        // successive element is larger than the one before it
        // CKA: The idea is good but you have to create a loop, and do this comparison on events from 0 to list.length-1:
        // for (int i = 0; i< list.length -1; i++) {
        //   if (list[i].compareTo(list[i+1]) > 0) { .... }
        // }
        if(list[0].compareTo(list[1])>0){
            sorted=false;
        }

        return sorted;
    }

    /**
     * Replaces all but the first and last with the larger of its to neighbors
     * You can use the compareTo to determine which string is larger (later in alphabetical
     * order).
     */
    public void replaceWithLargerNeighbor()
    {
        // CKA: First you have to make a copy of the array at first, or you are going to work on a modified array and 
        // it is not going to make the wanted effect. See java.util.Arrays.copyOf(...)
        // Second, you have to compare between previous and next elements, so do the comparison:
        // if (copy[a-1].compareTo(copy[a+1]) < 0) { list[a] = copy[a+1]; } else {list[a] = copy[a-1]; }
        for(int a=1;a<list.length-1;a++){
            
            if(list[a].compareTo(list[a+1])<0){
                
                list[a]=list[a+1];
                
                
            }
        }


    }

    /**
     * Gets the number of duplicates in the array.
     * (Be careful to only count each duplicate once. Start at index 0. Does it match any of the other element?
     * Get the next word. It is at index i. Does it match any of the words with index > i?)
     * @return the number of duplicate words in the array.
     */
    public int countDuplicates()
    {
        // CKA: First, you compare String instances with "equals", not with "==".
        // Second, after finding the first duplicate for list[a], use "break" to go out of the inner loop.
        int duplicates = 0;
        
        for(int a=0;a<list.length-1;a++){
            for(int b=a+1;b<list.length;b++){
                if(list[a]==list[b]){
                    duplicates++;
                }
            }
            
            
        }

        return duplicates;
    }

    /**
     * Moves any word that starts with x, y, or z to the front of the array, but
     * otherwise preserves the order
     */
    public void xyzToFront()
    {
        int insertAt = 0;
        
        for(int a=0;a<list.length;a++){
        if("xyz".contains(list[a].substring(0,1))){
            
            // CKA: it's good, in particular the idea of decrementing b, except three things:
            // - You should move elements to the right from index "a" to "insertAt+1", not from "length-1" to "insertAt+1".
            // - insertAt should be incremented not in this loop but in the end of the outer one (after assigning to list[insertAt]).
            // - When you come at the list[insertAt] = ..., the value of list[a] has been replaced and thus lost. You have 
            //   to save it in a temporary variable first, and add it to list[insertAt] afterwards.
            for (int b=list.length-1;b>insertAt;b--){
                list[b]=list[b-1];
                
                insertAt++;
               }
               list[insertAt]=list[a];
              
        }
            
           
        }

    }

    /**
     * gets the string representation of this array 
     * @return a string representation of the array. (do this with Arrays.toString(list))
     */
    public String toString()
    {
        return Arrays.toString(list);
    }
}