3 StringBuilder

Question 1

What is the default length of a StringBuilder object?

Answer 1

Length is different than capacity. The lenght is equal to the string argument passed. If no argument is passed, length =0. StringBuilder has length NOT size.

Question 2

Does StringBuilder object have a size?

Answer 2

No, it has length and capacity.

Question 3

What is the default capacity for a StringBuilder object and the constructor?

Answer 3

Default capacity is 16 when no specific capacity is passed to the constructor. String Builder sb = new StringBuilder(); // makes a sb object with capacity 16

Question 4

How do you write a constructor for a StringBuilder with a set capacity?

Answer 4

String Builder sb = new StringBuilder(5); //capacity set to 5

Question 5

How do you convert a StringBuilder to a String?

Answer 5

String s=sb.toString();

Question 6

What are the 10 methods for the StringBuilder class?

Answer 6

acddiilrst

append(),
 charAt(),
 delete(),
 deleteCharAt(),
indexOf(),
 insert(),
 length(),
 reverse(),
 substring(),
 and toString()

Question 7

T or F. A sb object is changed when a method performs an operation. An assignment is NOT required.

Answer 7

True, for most of the methods. subString & toString do not.
sb.append(‘x’) is the same as sb=sb.append(x)

Question 8

What index does StringBuilder start at?

Answer 8

Zero! sb.charAt(0) is the first letter.

Question 9

Which is a real StringBuilder method used to create the capacity of the sb object?
setCapacity(int num);
ensureCapacity(int num);

Answer 9

ensureCapacity(int num);

• there is no setCapacity method.

StringBuilder sb = new StringBuilder(); sb.ensureCapacity(100);