Question

The following Assignment Questions are related to Java Collection Interfaces (Queue, List, Map, Set, etc), and Java IOStream.

1. As mentioned at the beginning of our Collection’s class that the basis of java interfaces is mainly based on "TREES". However, one of these interfaces forms a different "TREE". Describe that particular interface. [1 Marks].
2. Why do we need to declare a type of object within each interface in the collection packages by "<E>" for example: <Integer, boolean, float, etc>”. [1 Marks].
3. How can we build an interface (list, set, etc) without having repeated (duplicated) items? [1 Marks].
4. Check the syntax of Advanced For Loop, if we use it over a List interface, you would notice that we cannot modify elements within that list. using the Iterator allows us to make some changes. Create a simple code that obtains a List <String> and uses the String.trim method to every item (element) within the created list. [3 Marks].
5. What method/class use for reading a segment of data that has determined index reference (positions) closed or at the end of a huge file [1 Marks].

6. Write a function that counts the occurrence of a specific letter (Eg. “a”) in a file. Where the letter can be defined at the prompt line (command line). [3 Marks].

Answer 1

1)

Collection and Map both are interfaces in java. util package but Collection is used to store objects and Map is used to store the objects for (key,value) based manner. Collection classes are used to store object in array format. and Map classes are used to store in (KEY,VALUE) pair format

2)

By defining a Interface/class generic you are making it type-safe i.e. it can act up on any datatype

We need because 1)Type check at compile time

2)code reuse

3)

Set is acollection that cann't contains dublicate elements

1)HashSet

2)LinkedHashSet

3)TreeSet

// Java program to demonstrate a Set

import java.util.*;
public class SetExample{
   public static void main(String[] args)
   {
       // Set demonstration using HashSet
       Set<String> hash_Set
           = new HashSet<String>();

       hash_Set.add("code");
       hash_Set.add("For");
       hash_Set.add("code");
       hash_Set.add("Example");
       hash_Set.add("Set");

       System.out.println(hash_Set);
   }
}

output:-

[Set, Example, code, For]

4)

List<String> trimmedStrings = new ArrayList<String>();
for(String s : originalStrings) { //Advanced for loop
trimmedStrings.add(s.trim());
}

originalStrings = trimmedStrings;

or

List<String> myList = Arrays.asList(" A", "B ", " C ");
return myList.stream().(str -> str.trim());

5)

class Myclass{

public static void main(String args[]){

int arr[]={1,2,3,4,5,6,7,8};

func(arr,arr.length);

}

public static func(int arr,int l){

for(int i=0;i<li++){

System.out.print(arr[i]);

}

}

}

6)

// C program to illustrate
// command line arguments
#include<stdio.h>

int main(int argc,char* argv[])
{
char counter;

int result;
   printf("Program Name Is: %s",argv[0]);
   if(argc==1)
       printf("\nNo Extra Command Line Argument Passed Other Than Program Name");
   if(argc>=2)
   {
counter=argv[1]

result=func(counter);

printf("%d",result);

return 0;
}

int func(char s){

int count=0;

char ch, file_name[25];
FILE *fp;

printf("Enter name of a file you wish to compare the element \n");
gets(file_name);

fp = fopen(file_name, "r"); // read mode

if (fp == NULL)
{
perror("Error while opening the file.\n");
exit(EXIT_FAILURE);
}

printf("The contents of %s file are:\n", file_name);

while((ch = fgetc(fp)) != EOF)
if(ch==s){

count++;

}

fclose(fp);
}

return count;
}
  
}