Java Reference
In-Depth Information
The
Scanner
class has other features, such as the ability to fi nd the next occurrence of a
token, skip tokens, and work with locales. However, the information provided in this sec-
tion is suffi cient for the types of questions that you can expect on the SCJP exam regarding
Scanner
.
Summary
This chapter covered the “API Contents” section of the SCJP exam objectives. We discussed
many useful classes in the Java language, starting with the primitive wrapper classes in
java
.lang
. Each primitive type has a corresponding class that is used to “wrap” the primitives
into objects. As of Java 5.0, a primitive type is automatically boxed into its corresponding
wrapper class and automatically unboxed whenever necessary.
Strings were discussed in detail, including the differences between the
String
,
String-
Builder
, and
StringBuffer
classes. The
String
class represents an immutable string of
characters.
StringBuilder
and
StringBuffer
represent mutable strings of characters, and
the two classes have the same method signatures and constructor parameters. The only dif-
ference between them is that
StringBuffer
is thread-safe and
StringBuilder
is not.
A key topic discussed in this chapter was the input and output of data, including the
difference between byte streams and character streams (readers and writers). Low-level
streams connect to the source of the data, and high-level streams are chained to existing
streams. We saw how to buffer data streams using the
BufferedInputStream
,
Buffered-
OutputStream
,
BufferedReader
, and
BufferedWriter
classes. We also discussed how to
read and write primitive types and strings using the
DataInputStream
and
DataOutput-
Stream
classes.
The
java.io.File
class represents the pathname of a fi le or directory, and the class
contains methods for determining information about the fi le or directory is represents. The
FileInputStream
and
FileOutputStream
classes read and write raw bytes to fi les, and the
FileReader
and
FileWriter
classes read and write characters streams to fi les. We saw how
to use the
format/printf
methods of the
PrintWriter
class to format strings. We also dis-
cussed the
Console
class, which represents the JVM environment's console.
Serialization refers to taking the state of an object and writing it to a stream. An object's
class must implement
java.io.Serializable
to be serialized. Use the
ObjectInputStream
and
ObjectOutputStream
classes to read and write objects to a stream.
We spent a large portion of this chapter discussing how to format numbers, currency,
dates, and strings, including how to use the
java.util.Locale
class to perform these
operations within a given locale. Use the
format
methods of the
java.text.Number
Format
class to format numbers and currency for a specifi c locale. The
DecimalFormat
class is a child class of
NumberFormat
and formats fl oating-point numbers for a specifi c
locale. We discussed how to use the
parse
method of
NumberFormat
to parse numbers
and currency. We also discussed how to format and parse dates using the
DateFormat
class of
java.text
.
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