Given the statement: private static final Map<String, Integer> counts = new Tree

Question

Given the statement:

private static final Map<String, Integer> counts = new TreeMap<>();

write a method buildWordCounts(based on buildIndex from page 332) that builds the Map object shown above.

Here is the first 4 lines of the code that was given to us:

public static void buildWordCounts(Scanner scan) {

        while (scan.hasNextLine()) {

            String token;

            while ((token = scan.findInLine("[\p{L}\p{N}']+")) != null) {

Sets and Maps already occurred on lines 4 and 8 and we encounter it again on line 20, the List associated with fire would reference three Integer objects wrapping the numbers 4,8, and 20. Listing 7.2 shows method buildIndex (adapted from buildIndex in Listing 6.8). Data field index is a Map with key type String and value type List

Explanation / Answer

class StringConstructorsDemo
{
   public static void main(String[] args)
   {
       String s1 = "abc";
       System.out.println("s1: "+s1); //abc

       String s2 = new String("abcd");
       System.out.println("s2: "+s2);//abcd
  
       char[] ch = {'x', 'y', 'z'};
       System.out.println("ch: "+ch);//[C@19821f

       System.out.print("ch: ");

       //if we want to print this array value we should use for loop, as shown below
       for ( int i = 0 ; i < ch.length; i++)
       {
           System.out.print(ch[i]);//xyz
       }

       System.out.println();
      
       //converting char array into String is more convenient than writting for loop, as shown below
       String s3 = new String(ch);
       System.out.println("s3: "+s3);//xyz

      
       //creating empty string
       String s4 = "";
       String s5 = new String();
       String s6 = new String("");
      
       System.out.println("s4: "+s4);
       System.out.println("s5: "+s5);
       System.out.println("s6: "+s6);

       //creating null string
       String s7 = null;
       //String s8 = new String(null); CE: ambiguous error
       //String s8 = new String((String)null); RE: NPE
       //String s8 = new String(s7); RE: NPE

       //We can create null String ref variable(s7), but we cannot create String object with null. It leads to NPE

       //creating String object from another String object
       String s8 = new String("A");
       String s9 = new String(s8);
       System.out.println("s8: "+s8);//A
       System.out.println("s9: "+s9);//A
       System.out.println(s8 == s9);//false
      
       //assigning one string object reference to another String reference variable
       String s10 = new String("B");
       String s11 = s10;
       System.out.println("s10: "+s10);//B
       System.out.println("s11: "+s11);//B
       System.out.println(s10 == s11);//true
   }
}

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