Which method of class StringBuffer is used to find the length of current character sequence in Java?

Java MCQs on StringBuffer class of Java Programming Language.

1. Which of these class is used to create an object whose character sequence is mutable?
a] String[]
b] StringBuffer[]
c] String[] & StringBuffer[]
d] None of the mentioned

Answer: b
Clarification: StringBuffer represents growable and writable character sequence.

2. Which of this method of class StringBuffer is used to concatenate the string representation to the end of invoking string?
a] concat[]
b] append[]
c] join[]
d] concatenate[]

Answer: b
Clarification: None.

3. Which of these method of class StringBuffer is used to find the length of current character sequence?
a] length[]
b] Length[]
c] capacity[]
d] Capacity[]

Answer: a
Clarification: None.

4. What is the string contained in s after following lines of Java code?

StringBuffer s new StringBuffer["Hello"]; s.deleteCharAt[0];

a] Hell
b] ello
c] Hel
d] llo

Answer: b
Clarification: deleteCharAt[] method deletes the character at the specified index location and returns the resulting StringBuffer object.

5. Which of the following statement is correct?
a] reverse[] method reverses all characters
b] reverseall[] method reverses all characters
c] replace[] method replaces first occurrence of a character in invoking string with another character
d] replace[] method replaces last occurrence of a character in invoking string with another character

Answer: a
Clarification: reverse[] method reverses all characters. It returns the reversed object on which it was called.

6. What will be the output of the following Java program?

1. class output
2. {
3. public static void main[String args[]]
4. {
5. String a = "hello i love java";
6. System.out.println[a.indexOf['e']+" "+a.indexOf['a']+" "+a.lastIndexOf['l']+" "+a.lastIndexOf['v']];
7. }
8. }

a] 6 4 6 9
b] 5 4 5 9
c] 7 8 8 9
d] 1 14 8 15

Answer: d
Clarification: indexof[‘c’] and lastIndexof[‘c’] are pre defined function which are used to get the index of first and last occurrence of
the character pointed by c in the given array.
Output:

$ javac output.java $ java output 1 14 8 15

7. What will be the output of the following Java program?

1. class output
2. {
3. public static void main[String args[]]
4. {
5. StringBuffer c = new StringBuffer["Hello"];
6. c.delete[0,2];
7. System.out.println[c];
8. }
9. }

a] He
b] Hel
c] lo
d] llo

Answer: d
Clarification: delete[0,2] is used to delete the characters from 0 th position to 1 st position.
Output:

$ javac output.java $ java output llo

8. What will be the output of the following Java program?

1. class output
2. {
3. public static void main[String args[]]
4. {
5. StringBuffer c = new StringBuffer["Hello"];
6. StringBuffer c1 = new StringBuffer[" World"];
7. c.append[c1];
8. System.out.println[c];
9. }
10. }

a] Hello
b] World
c] Helloworld
d] Hello World

Answer: d
Clarification: append[] method of class StringBuffer is used to concatenate the string representation to the end of invoking string.
Output:

$ javac output.java $ java output Hello World