Java Multiple Choice Questions & Answers on StringBuffer Methods for Freshers

1. Which of these method of class StringBuffer is used to extract a substring from a String object?

a) substring()
b) Substring()
c) SubString()
d) None of the mentioned

Answer: a

2. What will s2 contain after following lines of code?
StringBuffer s1 = “one”;
StringBuffer s2 = s1.append(“two”)

a) one
b) two
c) onetwo
d) twoone

Answer: c

Explanation: Two strings can be concatenated by using append() method.

3. Which of these method of class StringBuffer is used to reverse sequence of characters?

a) reverse()
b) reverseall()
c) Reverse()
d) reverseAll()

Answer: a

Explanation: reverse() method reverses all characters. It returns the reversed object on which it was called.

4. Which of these method of class StringBuffer is used to get the length of sequence of characters?

a) length()
b) capacity()
c) Length()
d) Capacity()

Answer: a

Explanation: length()- returns the length of String the StringBuffer would create whereas capacity() returns total number of characters that can be supported before it is grown.

5. Which of the following are incorrect form of StringBuffer class constructor?

a) StringBuffer()
b) StringBuffer(int size)
c) StringBuffer(String str)
d) StringBuffer(int size , String str)

Answer: d

6. What is the output of this program?

1.     class output {

2.         public static void main(String args[])

3.         { 

4.              StringBuffer c = new StringBuffer("Hello");

5.              System.out.println(c.length());

6.         }

7.     }

a) 4
b) 5
c) 6
d) 7

Answer: b

Explanation: length() method is used to obtain length of StringBuffer object, length of “Hello” is 5.

7. What is the output of this program?

1.   class output {  

2.       public static void main(String args[]) {  

3.           StringBuffer sb=new StringBuffer("Hello");  

4.           sb.replace(1,3,"Java");  

5.           System.out.println(sb);

6.       }  

7.   }

a) Hello java
b) Hellojava
c) HJavalo
d) Hjava

Answer: c

Explanation: The replace() method replaces the given string from the specified beginIndex and endIndex.

8. What is the output of this program?

1.     class output {

2.         public static void main(String args[])

3.         { 

4.            StringBuffer s1 = new StringBuffer("Hello");

5.            s1.setCharAt(1,'x');

6.            System.out.println(s1);

7.         }

8.     }

a) xello
b) xxxxx
c) Hxllo
d) Hexlo

Answer: c

9. What is the output of this program?

1.     class output {

2.         public static void main(String args[])

3.         {

4.            StringBuffer s1 = new StringBuffer("Hello World");

5.            s1.insert(6 , "Good ");

6.            System.out.println(s1);

7.         }

8.    }

a) HelloGoodWorld
b) HellGoodoWorld
c) HellGood oWorld
d) Hello Good World

Answer: d

Explanation: The insert() method inserts one string into another. It is overloaded to accept values of all simple types, plus String and Objects. Sting is inserted into invoking object at specified position. “Good ” is inserted in “Hello World” T index 6 giving “Hello Good World”.

10. What is the output of this program?

1.     class output {

2.         public static void main(String args[])

3.         { 

4.            StringBuffer s1 = new StringBuffer("Hello");

5.            s1.insert(1,"Java");

6.            System.out.println(s1);

7.         }

8.     }

a) hello
b) java
c) Hello Java
d) HelloJava

Answer: d

Explanation: Insert method will insert string at a specified position