This section of our 1000+ Java MCQs focuses on string handling in Java Programming Language.
1. Which of these class is superclass of String and StringBuffer class?
a) java.util
b) java.lang
c) ArrayList
d) None of the mentioned
View Answer
Explanation: String and StringBuffer are part of the java.lang package, which means they inherit from the Object class, the root of the Java class hierarchy.
2. Which of these operators can be used to concatenate two or more String objects?
a) +
b) +=
c) &
d) ||
View Answer
Explanation: Operator + is used to concatenate strings, Example String s = “i ” + “like ” + “java”; String s contains “I like java”.
3. Which of this method of class String is used to obtain a length of String object?
a) get()
b) Sizeof()
c) lengthof()
d) length()
View Answer
Explanation: Method length() of string class is used to get the length of the object which invoked method length().
4. Which of these method of class String is used to extract a single character from a String object?
a) CHARAT()
b) chatat()
c) charAt()
d) ChatAt()
View Answer
Explanation: charAt() is a predefined method of String class which returns the character at the given index.
5. Which of these constructors is used to create an empty String object?
a) String()
b) String(void)
c) String(0)
d) None of the mentioned
View Answer
Explanation: The String() invokes the default constructor of String class and returns the object of NULL String.
6. Which of these is an incorrect statement?
a) String objects are immutable, they cannot be changed
b) String object can point to some other reference of String variable
c) StringBuffer class is used to store string in a buffer for later use
d) None of the mentioned
View Answer
Explanation: StringBuffer class is used to create strings that can be modified after they are created.
7. What will be the output of the following Java program?
class String_demo{public static void main(String args[])
{char chars[] = {'a', 'b', 'c'};
String s = new String(chars);
System.out.println(s);
}}
a) a
b) b
c) c
d) abc
View Answer
Explanation: String(chars) is a constructor of class string, it initializes string s with the values stored in character array chars, therefore s contains “abc”.
output:
$ javac String_demo.java
$ java String_demo
abc8. What will be the output of the following Java program?
class String_demo{public static void main(String args[])
{int ascii[] = { 65, 66, 67, 68};
String s = new String(ascii, 1, 3);
System.out.println(s);
}}
a) ABC
b) BCD
c) CDA
d) ABCD
View Answer
Explanation: ascii is an array of integers which contains ascii codes of Characters A, B, C, D. String(ascii, 1, 3) is an constructor which initializes s with Characters corresponding to ascii codes stored in array ascii, starting position being given by 1 & ending position by 3, Thus s stores BCD.
output:
$ javac String_demo.java
$ java String_demo
BCD9. What will be the output of the following Java program?
class String_demo{public static void main(String args[])
{char chars[] = {'a', 'b', 'c'};
String s = new String(chars);
String s1 = "abcd";
int len1 = s1.length();
int len2 = s.length();
System.out.println(len1 + " " + len2);
}}
a) 3 0
b) 0 3
c) 3 4
d) 4 3
View Answer
Explanation: The String s is created by passing the array of characters, while String s1 is created using auto unboxing with 4 characters, Because the length() method returns the no. of character in the string. Hence output is 4 3.
output:
$ javac String_demo.java $ java String_demo 4 3
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