CSIS 110 โ Lecture 37
Announcements: Practice exam next week. Read 12.5.2, 12.5.3.
Last Time: String and StringBuffer
What are some major differences between the String and StringBuffer classes?
- Strings are immutable (value cannot be changed)
- StringBuffer class contains methods that change the value of a StringBuffer object
- String has special syntax for initialization and concatenation
Did you have to import anything to use StringBuffer? Why not? Because it is in the
java.lang package, which gets imported automatically.
The StringBuffer class is similar to String, except that StringBuffer objects can be
modified. Let's look at some methods provided by the StringBuffer class:
append โ add some characters to the end of the StringBuffer
insert โ insert characters in the middle of the StringBuffer
setCharAt โ change the character at position p to a new value
deleteCharAt โ delete the character at position p
toString โ return a String representation of the StringBuffer
Also has methods like the String class: length, charAt.
Constructors:
StringBuffer()
StringBuffer( String s )
Exceptions
Let's look at the problems project. The Example class includes three public methods.
Don't execute these methods yet!
Remind students about array initialization.
Let's look at the loop1 method. What is wrong with it? What will happen when we run it?
How about the listExample method? What's going to happen when we run it?
What about the getUserInput method? Is it correct?
Java throws an Exception when something goes wrong that it cannot recover from.
A couple of weeks ago, we said that there were two types of errors that we could make
when we wrote a program: syntax errors and logic errors.
