Question

java programming

Concepts

ArrayList - Collections

Sorting

Enhanced For Loop

Collections Class

Auto-boxing

Programming Assignment

1. Describe auto-boxing, including why it is useful. (Google for this one) Write a few lines of code that auto-box an int into an Integer, and un-box an Integer to an int.

2. Declare an ArrayList of Strings. Add 5 names to the collection. "Bob" "Susan" ... Output the Strings onto the console using the enhanced for loop.

3. Sort the list using the method Collections.sort. Output the sorted List. Shuffle the list, and output the shuffled list. Note that Collections (with an s) is a class, while Collection is an interface. The Collections class has many useful static methods for processing interfaces, including the sort method.

4. Search for the name "Susan" in the list. What location was it found? Search for a name that is not in the list. What location is reported?

5. Describe why an equals method and a compareTo method are required to achieve searching and sorting of the elements of a list.

6. Convert the list above to an array using toArray. Output the elements of the array. Convert the array back into a list using asList. Output the elements of the list.

Submission.

Please submit .java file(s)

Answer 1

import java.util.*;
public class Main
{
   public static void main(String[] args) {
       System.out.println("Hello World");
       //1
       //auto-boxing and un-boxing are used for auto-typcasting from primitive type to object and object to primitive type
      
       //auto-boxing
       Integer n = 24;
       //un-boxing
       int m = n;
       System.out.println(n+" "+m);
      
       //2
       ArrayList<String> a1= new ArrayList<String>();
       //adding 5 names
a1.add("Bob");
a1.add("Susan");
a1.add("John");
a1.add("Sherlock");
a1.add("Bobby");
  
//outputing names through loop
for(int i=0;i<a1.size();i++)
System.out.println(a1.get(i));
//3
//sorting
Collections.sort(a1);
//printing list
System.out.println("Sorted list :"+a1);
//shuffling list
Collections.shuffle(a1);
System.out.println("Shuffled list :"+a1);
  
//4
//searching for Susan
int k=-1;
for(int i=0;i<a1.size();i++)
if(a1.get(i).equals("Susan"))//here equals is used to compare two string objects
k=i;//if found
if(k<=0)System.out.println("Susan not found");
else System.out.println("Susan found at index : "+k);
  
//searching for string that is not in the list
k=-1;
for(int i=0;i<a1.size();i++)
if(a1.get(i).equals("Fisher"))//here equals is used to compare two string objects
k=i;//if found

if(k<=0)System.out.println("Fisher not found");
else System.out.println("Fisher found at index : "+k);
  
//5 //here equals is used to compare two string objects
  
  
//6
//converting to array
  
Object a[] = a1.toArray();
//printing Array
for(int i=0;i<a.length;i++)
System.out.println(a);
  
  
  
}
}