Question

1. Why must getline() be used instead of cin to get string input?
   2. Give an example of when you would need to use cin.ignore() in your code
   3. Strings in C++ are mutable, this is different than in Java where strings were immutable. What do we mean by mutable versus immutable?
   4. Imagine your code had the following string variable in it string message = "HH231JJ"; Write a for loop that uses the [ ] operator to change each 'H' character in the message string to a '#' character.

Answer 1

Answer a.

Code Explanation

#include <iostream>
#include <string>

using namespace std;

int main(){
string str, str1;

/*cin is not able to read string with more than one word
thats why we use getline()*/

cout<<"Enter string using getline: ";
getline(cin, str1);
cout<<"Enter string using cin: ";
cin>>str;

cout<<"cin string: "<<str<<endl;
cout<<"getline string: "<<str1;
}

Output

Answer b

When you use cin for input it takes space " ", "\t", "\n" as a delimiter character. It doesn't display it but stores it in the buffer, for example,

int a;

string str

cin>>a

//use cin.ignore() here to make it work properly

getline(cin, str);

After you press in cin it will skip the getline() because the getline() will read "\n". So to flush the buffer, we use cin.ignore().

Answer c

In Java, strings are immutable which means that once the value stored in the string variable it cannot be changed. If you change the value it will allocate a new space in the string pool memory for that new value. But in C++ the strings are mutable which means that the stored value can be changed without allocating new memory in the string pool. We can achieve string mutability in Java as well using StringBuilder and StringBuffer.

Answer d

Code Explanation

#include <iostream>
#include <string>

using namespace std;

int main(){
string str="HH231JJ";
for(int i=0; i<str.length(); i++){
//using [] operator to find H
if(str[i]=='H'){
str[i]='#';//replacing H with #
}
}
cout<<str;
}

Output