Summary: Using Classes and Objects

In this lesson, we will look the important points we covered in this chapter.

We'll cover the following...

The Java Class Library, which contains a collection of standard classes that we can use in our programs, is organized into packages of classes.
We use the operator new to create a new object of a class type.
A variable of a primitive data type contains the actual value of the data it represents. A variable of a class type contains a reference to the object that it represents.
Characters within strings are represented by Unicode values.
Certain escape characters are written as two characters. For example, the new-line character is \n.
Methods within the class String enable us to manipulate strings. For example, we can join two strings end to end, get the length of a string, get the character at a certain position, locate a substring, and compare strings.
We can use the class Scanner to extract tokens from a string that is either defined in our program or read as data. By default, white space separates the tokens, but we can define other characters as delimiters.
An object of the class LocalTime represents the time that it was created. We can compare two such objects and decide which one represents the earlier time.
The class BigDecimal provides accurate decimal arithmetic with arbitrarily large numbers.
A wrapper class such as Integer represents primitive data as an object. Integer contains the method parseInt that converts a string containing an integer to an int. It also defines constants that represent the minimum and maximum values of an int value.
The class Random has methods to generate numbers that appear to be random.
The class DecimalFormat enables us to format the output of a real number or an integer according to a pattern that we create.