Which of this method of class stringbuffer is used to reverse sequence of characters?

Java MCQs on StringBuffer class of Java Programming Language.

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• Which of this method of class StringBuffer is used to reverse sequence of characters?
• Which of this method of class StringBuffer is used to concentrate the String representation to the end of invoking String?
• Which method can be used to set the length of the buffer within a StringBuffer object?
• Which of this method of class String is used to obtain a length of String object?

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