Summary

In this chapter, we looked at popular classes from the Java Core API. We started with Scanner, a useful class for reading input. Scanner can be directed to read from a file, a String object, or the keyboard. Reading from the keyboard is particularly useful for dealing with user input.

We examined the String class and its API. We saw how String literals use the string constant pool to save on memory. We examined an important property of String objects, namely immutability. A String object, once created, cannot be changed.

Next, we examined StringBuilder and its API. We discussed that StringBuilder is a mutable type and thus, there is only ever one object in memory.

Given that String is immutable but StringBuilder is mutable, we presented a detailed example with both code and supporting diagrams to compare and contrast String and StringBuilder.

This led to a discussion on how to create our own custom immutable types. We examined a checklist of steps you must perform...