Object Oriented Programming (OOPs) Multiple Choice Questions & Answers (MCQs) on “String Class”.
1. Which is a true statement for object of String class?
a) Object are immutable
b) Object are mutable
c) Object are created only once
d) Object can’t be created
Clarification: The object of string class are mostly immutable. This means that the String objects are constant. These can’t be changed once created.
2. How to declare an object of class String?
a) String object_Name = value;
b) String object_name = new;
c) String object_name= new value;
d) String object_name= value new;
Clarification: The class name String is given. And then the object name is mentioned. There are two ways to declare and initialize the string. Either by giving direct string value or by using new keyword. But if new operator is used, constructor of String class have to be called. From the given options, the direct string value declaration is correct.
3. What does function length do in String class?
a) Returns length of string including null character
b) Returns length of string excluding null character
c) Returns length of substring
d) Returns size of string in bytes
Clarification: The length function returns the length of string. The length is the number of characters in the string but the last null character is not counted. The string length can be used to loop through each character in the string.
4. Which is the function to get the character present at a particular index in the string?
a) char charAt(index);
b) char charIn(StringName);
c) char charAt(StringName);
d) char charIn(index);
Clarification: The function can be called using dot operator with the string object. Char is the return type of the function to return the character at specified position. The index must be an integer value, less than the length of string.
5. If only one parameter is passed to substring function then __________________
a) It returns the character at the specified position
b) It returns the string of length 1 from the specified index
c) It returns the string from specified index till the end
d) It returns the string from starting of string till the specified index
Clarification: The substring function returns a string value. The string is the substring starting from the specified index till the end. The substring function have to be called with the object of string class.
6. If two index are given as argument to substring function then ___________________
a) String of length equal to sum of two arguments is returned
b) String starting from first index and of length equal to send argument
c) String starting from first index and of length equal to sum of two arguments
d) String starting from first index and ending at second index position
Clarification: A value of string type is returned from this function. The returned string is a substring that starts from the first argument position, till the second index position. The indices must be less than the length of actual string.
7. String class have a concat() function that is used to _____________________
a) Replace old string by new string
b) Add two strings
c) Append one string at end of another string
d) Remove a string from end of one string
Clarification: The concat function is used to append string into another string. The new string is always appended at the end of source string. The target string is appended as it is and the whole string is then ended by null character.
8. The function lastIndexOf() is used to ___________________
a) Get the index of last occurrence of specified character in argument
b) Get the index of first occurrence of specified character in argument
c) Get the index of last occurrence of first character in string
d) Get the index of last occurrence of last character of string
Clarification: The function is used to get the last occurrence index of a character present in a string. The return type is char. Single character is returned. The function is used with a string object and the target character is passed as its argument.
9. Function equals() is _______________ and equalIgnoreCase() is _________________
a) Case Insensitive, case insensitive
b) Case sensitive, Case insensitive
c) Case sensitive, case sensitive
d) Case insensitive, case sensitive
Clarification: Both the functions return Boolean value. The function equal() is case sensitive and returns false even if a single character is case different in two strings. The other function ignores the case sensitivity and only checks if the spellings are same.
10. The compareTo() function is used to ________________
a) Compare strings value to string object
b) Compare string value to string value
c) Compare string object to another string object
d) Compare string object to another string value
Clarification: The source and target must be objects of the string class. The compare is always case sensitive. To compare two string objects without case sensitivity then we can use compareToIgnoreCase() function.
11. String class provides function toUpper() to _____________________
a) Convert first character to uppercase
b) Convert last character to uppercase
c) Convert the whole string characters to uppercase
d) Convert uppercase to lower and lower to uppercases
Clarification: The function is used to convert each character of the string. If the character is already uppercase then it remains the same. But if some character is in lowercase then it will be converted to uppercase.
12. String trim() function is used to _______________________
a) Remove all the white spaces from the string
b) Remove white space from start of string
c) Remove white space at end of string
d) Remove white space from both the ends of string
Clarification: The function is used to remove any white space from both the ends of a given string. The white space include space, tab, next line etc. It will be removed both from the starting of string and from the end of string.
13. Function replace() accepts _____________ arguments.
Clarification: The first argument is the target character. This target character will be replaced by another character. The new character is the second argument to the function. Only the characters can be passed as argument, not a string.
14. If two arguments are passed to the indexOf() function then ___________________
a) Second argument indicates the occurrence number of specified character from starting
b) Second argument indicates the occurrence number of specified character from end
c) Second argument indicates the index of the character in first argument
d) Second argument indicates the index of the character from the last of the string
Clarification: The string may have more than one occurrence of a character. We use this function to get the index at which the specified number of times a specific character has occurred in a string. For example, we can get the index of 5th occurrence of character “j” in a string.
15. The string class deals with string of only character type.
Clarification: The string class objects can be used for any string consisting of characters. The characters include numbers, alphabets and few special characters. String class is not necessary to be used but provides a huge set of inbuilt functions to make the string operations easier.