Analyze the following code.

Question

```
class Test {
public static void main(String[] args) {
StringBuilder strBuf = new StringBuilder(4);
strBuf.append("ABCDE");
System.out.println("What's strBuf.charAt(5)? " + strBuf.charAt(5));
}
}
```
a. The program has a compile error because you cannot specify initial capacity in the StringBuilder constructor.
b. The program has a runtime error because because the buffer's capacity is 4, but five characters "ABCDE" are appended into the buffer.
c. The program has a runtime error because the length of the string in the buffer is 5 after "ABCDE" is appended into the buffer. Therefore, strBuf.charAt(5) is out of range.
d. The program compiles and runs fine.

Answer 1

c. The program has a runtime error because the length of the string in the buffer is 5 after "ABCDE" is appended into the buffer. Therefore, strBuf.charAt(5) is out of range.
The charAt method returns the character at a specific index in the string buffer. The first character of a string buffer is at index 0, the next at index 1, and so on. The index argument must be greater than or equal to 0, and less than the length of the string buffer.