Download IO18

Input and Output
Text and Binary I/O
Chapter 19
Introduction to Java Y.Daniel Liang
1
File Input and Output
Programs to run are in the FileIO folder:
1. ScannerDriver.java
2. ScannerFile.java
ScannerTextfile.txt
ScannerOutputfile.txt
3. Inventory.java (Driver)
InventoryItem.java
input file: inventory.txt
(input file)
(output file)
Introduction to Java Y.Daniel Liang
2
File Input and Output
Programs to run contd.
4. TestPrint.java
5. TestPrintWriter.java Team #1
output file: pw.txt
6. TestFileStream Team #2
7. TestDataStream Team #3
output file: temp.dat
Introduction to Java Y.Daniel Liang
3
File Input and Output
Programs to run contd.
8. Copy.java Team #4
Welcome.java (source file)
Temp. java (target file)
9. TestObjectStreamForArray Team #5
Introduction to Java Y.Daniel Liang
4
Objectives
•To understand how I/O is processed in Java
•To distinguish between text I/O and binary
I/O
•To read data from the console using the
Scanner class
•To read data from a file using the Scanner
class
Introduction to Java Y.Daniel Liang
5
Objectives contd.
•To write data to a file using the PrintWriter
class
•To read and write bytes using FileInput
Stream and FileOutputStream
•To read and write primitive values and
strings using DataInputStream/
DataOutPutStream
Introduction to Java Y.Daniel Liang
6
Objectives contd.
•To store and restore objects using
ObjectOutputStream and ObjectInputStream
and to understand how objects are serialized
and what kind of objects can be serialized
To use the Serializable interface to enable
objects to be serializable
To know how to serialize arrays
Introduction to Java Y.Daniel Liang
7
Input and Output
Introduction
Data held in variables, arrays, and objects are
temporary. Data are lost when the program
ceases processing
To save the data created during the life of the
program, you must save the data in a file onto a
disk, CD, or some other storage device .
Then the file can be transported and can be
read later by other programs
Introduction to Java Y.Daniel Liang
8
Introduction
Redirection of Input and Output
It is tedious to test programs by typing data in for every test run.
Testing is far easier if the program reads input from a file.
You can prepare the file once and reuse it for many tests.
The command line interfaces of most operating systems provide a way
to link a file to the input of a program, as if all the characters in the
file had actually been typed by the user .
Introduction to Java Y.Daniel Liang
9
Introduction
Redirection of Input and Output example:
java ClassName < data.txt > output.txt
Use input redirection to avoid repetitive typing during testing.
Use output redirection to save your program output in a file.
Introduction to Java Y.Daniel Liang
10
Introduction contd.
Data are stored in two basic formats:
text and binary
Text file is represented in human-readable form
Examples of text files that you can read:
Files that are created with a simple text exitor ,
such as Windows Vista NotePad, as well as Java
source code, and HTML Files
Introduction to Java Y.Daniel Liang
11
Introduction contd.
Data stored in a binary file are represented in binary
form. You cannot read binary files. The files are
designed to be read by programs.
Binary files consists of a series of bits
Text file consist of a series of characters.
Introduction to Java Y.Daniel Liang
12
Introduction contd.
The advantages of binary files are that:
1. They are more efficient to process than text
files. Text I/O requires encoding and decoding
whereas binary I/O does not.
2. Binary files are independent of the encoding
scheme on the host machine and thus are
portable.
Introduction to Java Y.Daniel Liang
13
The Scanner class
The simplest tool for reading text files is the
Scanner class.
Class java.util.Scanner
Introduction to Java Y.Daniel Liang
14
to Get Input from the Console Using the Scanner Class
Run ScannerDriver program in the FileIO Folder
next(): reading a string. A string delimeter is a space
nextByte(): reading an integer of the byte type
nextShort(): reading an integer of the short type
nextInt(): reading an integer of the int type
nextLong(): reading an integer of the long type
nextFloat(): reading a number of the float type
nextDouble(): reading number of the double type
Introduction to Java Y.Daniel Liang
15
To Get Input from a text file Using the Scanner Class
Run ScannerFile Program in the FileIO Folder
The action of reading data from a
file is called file input.
Introduction to Java Y.Daniel Liang
16
To read text data from a disk file, we use the FileReader and
BufferedReader objects.
• We first construct a FileReader object
with the name of the file
• Then we associate a BufferedReader object to the file.
• Then we read data, using the readLine method of the
BufferedReader class.
• Finally, we convert the String to a primitive data type as
necessary.
• Run Programs: InventoryItem (Driver)
Inventory
Use input file: inventory.txt
Introduction to Java Y.Daniel Liang
17
Sample code for processing a text file:
String file = “customer.txt”;
String line;
try{
FileReader fr = new FileReader (file);
BufferedReader inFile = new BufferedReader(fr);
line = inFile.readLine();
while(line != null && count < MAX) {
tokenizer = new StringTokenizer(line);
name = tokenizer.nextToken();
Introduction to Java Y.Daniel Liang
18
Cont’d.
try{
custNumber = Long.parseLong (tokenizer.
nextToken());
balance = Double.parseDouble(tokenizer.
nextToken());
phone = tokenizer.nextToken();
custsArray[count++] = new Customer(name,
custNumber, balance, phone);
} // end inner try block
catch (NumberFormatException e) { }
line = inFile.readLine();
}// end while block
inFile.close();
Introduction to Java Y.Daniel Liang
19
PrintWriter is an object we use to generate an output text
file.
PrintWriter supports only two output methods:
print
println (for print line)
Run program TestPrinterWriter
output file: pw.txt
Introduction to Java Y.Daniel Liang
20
Constructors of the
PrintWriter
• PrintWriter(Writer out)
• PrintWriter(Writer out, boolean
autoFlush)
• PrintWriter(OutputStream out)
• PrintWriter(OutputStream out, boolean
autoFlush)
Introduction to Java Y.Daniel Liang
21
PrintWriter Methods
• void print(Object o)
• void print(String s)
• void println(String s)
• void print(char c)
• void print(char[] cArray)
•
•
•
•
void
void
void
void
print(int i)
print(long l)
print(float f)
print(double d)
• void print(boolean b)
Introduction to Java Y.Daniel Liang
22
Streams
In Java, all I/O is handled in streams.

A stream is an abstraction of the continuous one-way flow of data. The program

receives data thru the input stream and sends data thru the output stream.
Any source of input or destination for output is called a stream.
Input Stream
Program
File
Output Stream
Introduction to Java Y.Daniel Liang
23
Streams
 All
streams except random-access file
streams flow in only one direction;
therefore if you want to input and output,
you need two separate stream objects.
 Streams
are objects. Stream objects have
methods that read and write data , flush the
stream, close the stream, and count the
number of bytes in the stream, etc.
Introduction to Java Y.Daniel Liang
24
Binary I/O
Text I/O requires encoding and decoding. The JVM converts a
Unicode to a file specific encoding when writing a character and
coverts a file specific encoding to a Unicode when reading a
character.
Binary I/O does not require conversions. When you write a byte to
a file, the original byte is copied into the file. When you read a byte
from a file, the exact byte in the file is returned.
Text I/O program
(a)
The Unicode of
the character
e.g. "199"
,
Encoding/
Decoding
The encoding of the character
is stored in the file
00110001 00111001 00111001
0x31
0x39
0x39
Binary I/O program
(b)
A byte is read/written
e.g. 199
,
The same byte in the file
00110111
0xC7
Introduction to Java Y.Daniel Liang
25
25
Binary I/O Classes
The design of the Java I/O classes is a good example of
applying inheritance, where common methods are generalized
in superclasses, and sub classes provide specialized methods.
See next slide. It list some of the classes for performing
binary I/O.
InputStream is the root for binary input classes.
OutputStream is the root for binary output classes
Introduction to Java Y.Daniel Liang
26
Binary I/O Classes
FileInputStream
DataInputStream
InputStream
FilterInputStream
BufferedInputStream
ObjectInputStream
Object
OutputStream
FileOutputStream
BufferedOutputStream
FilterOutputStream
DataOutputStream
ObjectOutputStream
PrintStream
Introduction to Java Y.Daniel Liang
27
27
Stream Classes

The stream classes can be categorized into two types: byte
streams and character streams.

The InputStream/OutputStream class is the
root of all byte stream classes,

the Reader/Writer class is the root of all character
stream.

The subclasses of InputStream/
OutputStream are analogous to the
subclasses of Reader/Writer.
Introduction to Java Y.Daniel Liang
28
To Read and Write Binary Data from /To a Disk File
FileInputStream and FileOutputStream- all methods in these
classes are inherited from InputStream and OutputStream
(java.io. FileInputStream and java.io.FileOutputStream )
Create a FileInputStream:
FileInputStream inputStream = new
FileInputStream inputStream (
“input.bin”);
To write Binary Data to a Disk File:
FileOutputStream outputStream = new
FileOutputStream outputStream (
“output.bin”);
Introduction to Java Y.Daniel Liang
29
InputStream
java.io.InputStream

int read(byte[] b) throws IOException
abstract int read() throws IOException

void close() throws IOException

int available() throws IOException

long skip(long n) throws IOException

Note: The abstract InputStream class defines
the methods for the input stream of bytes
Introduction to Java Y.Daniel Liang
30
OutputStream
java.io.OutputStream

abstract void write(int b) throws
IOException

void write(byte[] b) throws IOException

void close() throws IOException

void flush() throws IOException

Note: The abstract OutputStream class
defines the methods for the output
stream of bytes.
Introduction to Java Y.Daniel Liang
31
FileInputStream/FileOutputStream
FileInputStream
DataInputStream
InputStream
FilterInputStream
BufferedInputStream
ObjectInputStream
Object
OutputStream
FileOutputStream
BufferedOutputStream
FilterOutputStream
DataOutputStream
ObjectOutputStream
PrintStream
FileInputStream/FileOutputStream associates a
binary input/output stream with an external file.
All the methods in
FileInputStream/FileOuptputStream are inherited
from its superclasses.
Introduction to Java Y.Daniel Liang
32
FileInputStream
To construct a FileInputStream, use the following
constructors:
public FileInputStream(String filename)
public FileInputStream(File file)
A java.io.FileNotFoundException would occur if you attempt to
create a FileInputStream with a nonexistent file.
Introduction to Java Y.Daniel Liang
33
FileOutputStream
To construct a FileOutputStream, use the following constructors:
public FileOutputStream(String filename)
public FileOutputStream(File file)
public FileOutputStream(String filename, boolean append)
public FileOutputStream(File file, boolean append)
If the file does not exist, a new file would be created. If the file already
exists, the first two constructors would delete the current contents in
the file. To retain the current content and append new data into the
file, use the last two constructors by passing true to the append
parameter.
Introduction to Java Y.Daniel Liang
34
FileOutputStream
The program TestFileStream uses binary I/O to
write ten bytes values from 1 to 10 to a file
named temp.dat
TestFileStream
Introduction to Java Y.Daniel Liang
Run
35
FilterInputStream/FilterOutputStream
FileInputStream
DataInputStream
InputStream
FilterInputStream
BufferedInputStream
ObjectInputStream
Object
OutputStream
FileOutputStream
BufferedOutputStream
FilterOutputStream
DataOutputStream
ObjectOutputStream
PrintStream
Filter streams are streams that filter bytes for some purpose. The basic byte input stream provides
a read method that can only be used for reading bytes.
If you want to read integers, doubles, or strings, you need a filter class to wrap the byte input
stream. Using a filter class enables you to read integers, doubles, and strings instead of bytes and
characters. FilterInputStream and FilterOutputStream are the base classes for filtering data.
When you need to process primitive numeric types, use DatInputStream and DataOutputStream
to filter bytes.
Introduction to Java Y.Daniel Liang
36
DataInputStream/DataOutputStream
DataInputStream reads bytes from the stream
and converts them into appropriate primitive
type values or strings.
FileInputStream
DataInputStream
InputStream
FilterInputStream
BufferedInputStream
ObjectInputStream
Object
OutputStream
FileOutputStream
BufferedOutputStream
FilterOutputStream
DataOutputStream
ObjectOutputStream
PrintStream
DataOutputStream converts primitive type values
or strings into bytes and output the bytes to the
stream.
Introduction to Java Y.Daniel Liang
37
DataInputStream
DataInputStream extends FilterInputStream
and implements the DataInput interface.
InputStream
FilterInputStream
DataInputStream
+DataInputStream(
in: InputStream)
java.io.DataInput
+readBoolean(): boolean Reads a Boolean from the input stream.
+readByte(): byte
Reads a byte from the input stream.
+readChar(): char
Reads a character from the input stream.
+readFloat(): float
Reads a float from the input stream.
+readDouble(): float
Reads a double from the input stream.
+readInt(): int
Reads an int from the input stream.
+readLong(): long
Reads a long from the input stream.
+readShort(): short
Reads a short from the input stream.
+readLine(): String
Reads a line of characters from input.
+readUTF(): String
Reads a string in UTF format.
Introduction to Java Y.Daniel Liang
38
DataOutputStream
DataOutputStream extends FilterOutputStream and implements the
DataOutput interface.
OutputStream
FilterOutputStream
DataOutputStream
+DataOutputStream(
out: OutputStream)
java.io.DataOutput
+writeBoolean(b: Boolean): void Writes a Boolean to the output stream.
+writeByte(v: int): void
Writes to the output stream the eight low-order bits
of the argument v.
+writeBytes(s: String): void
Writes the lower byte of the characters in a string to
the output stream.
+writeChar(c: char): void
Writes a character (composed of two bytes) to the
output stream.
+writeChars(s: String): void
Writes every character in the string s, to the output
stream, in order, two bytes per character.
+writeFloat(v: float): void
Writes a float value to the output stream.
+writeDouble(v: float): void
Writes a double value to the output stream.
+writeInt(v: int): void
Writes an int value to the output stream.
+writeLong(v: long): void
Writes a long value to the output stream.
+writeShort(v: short): void
Writes a short value to the output stream.
+writeUTF(s: String): void
Writes two bytes of length information to the output
stream, followed by the UTF representation of
every character in the string s.
Introduction to Java Y.Daniel Liang
39
Characters and Strings in Binary I/O
A Unicode consists of two bytes. The
writeChar(char c) method writes the Unicode of
character c to the output.
The writeChars(String s) method writes the
Unicode for each character in the string s to the
output.
Introduction to Java Y.Daniel Liang
40
Characters and Strings in Binary I/O
Why UTF-8? What is UTF-8?
UTF-8 (8-bit UCS/Unicode Transformation Format) is a coding
scheme that allows systems to operate with both ASCII and Unicode
efficiently. Most operating systems use ASCII.
Java uses Unicode. The ASCII character set is a subset of the
Unicode character set. Since most applications need only the ASCII
character set, it is a waste to represent an 8-bit ASCII character as a
16-bit Unicode character.
Introduction to Java Y.Daniel Liang
41
41
Characters and Strings in Binary I/O
Why UTF-8? What is UTF-8?
The UTF-8 is an alternative scheme that stores a character using 1, 2,
or 3 bytes. ASCII values (less than 0x7F) are coded in one byte.
Unicode values less than 0x7FF are coded in two bytes. Other
Unicode values are coded in three bytes.
Introduction to Java Y.Daniel Liang
42
42
Using DataInputStream/DataOutputStream
Data streams are used as wrappers on existing input and output
streams to filter data in the original stream. They are created using the
following constructors:
public DataInputStream(InputStream instream)
public DataOutputStream(OutputStream outstream)
The statements given below create data streams. The first statement
creates an input stream for file in.dat; the second statement creates an
output stream for file out.dat.
DataInputStream infile =
new DataInputStream(new FileInputStream("in.dat"));
DataOutputStream outfile =
new DataOutputStream(new FileOutputStream("out.dat"));
Introduction to Java Y.Daniel Liang
Using DataInputStream/DataOutputStream
DataInputStream and DataOutputStream read and write data primitive
types values and strings in a machine-independent fashion.
Thereby enabling you to write a data file on one machine and read it
on another machine that has a different operating system or file
structure.
An application uses a data output stream to write data that can later be
read by a program using a data input stream.
Introduction to Java Y.Daniel Liang
Using DataInputStream/DataOutputStream
The TestDataStream program writes student names and
scores to a file named temp.dat and reads the data back from
the file.
TestDataStream
Introduction to Java Y.Daniel Liang
Run
Order and Format
See program TestDataStream
CAUTION: You have to read the data in the same order and same
format in which they are stored. For example, since names are written
in UTF-8 using writeUTF, you must read names using readUTF.
Checking End of File
TIP: If you keep reading data at the end of a stream, an EOFException
would occur. So how do you check the end of a file? You can use
input.available() to check it. input.available() == 0 indicates that it is
the end of a file.
Introduction to Java Y.Daniel Liang
46
BufferedInputStream/BufferedOutputStream
Reduces the number of reads and writes
Using buffers to speed up I/O
FileInputStream
DataInputStream
InputStream
FilterInputStream
BufferedInputStream
ObjectInputStream
Object
OutputStream
FileOutputStream
BufferedOutputStream
FilterOutputStream
DataOutputStream
ObjectOutputStream
PrintStream
BufferedInputStream/BufferedOutputStream does not contain new
methods.
All the methods BufferedInputStream/BufferedOutputStream are inherited
from the InputStream/OutputStream
classes.
47
Introduction to Java Y.Daniel Liang
47
Constructing
BufferedInputStream/BufferedOutputStream
// Create a BufferedInputStream
public BufferedInputStream(InputStream in)
public BufferedInputStream(InputStream in, int bufferSize)
// Create a BufferedOutputStream
public BufferedOutputStream(OutputStream out)
public BufferedOutputStream(OutputStream out, int bufferSize)
Introduction to Java Y.Daniel Liang
48
Constructing
BufferedInputStream/BufferedOutputStream
Improve the performance of the TestDataStream program by
adding buffers in the streams in lines 6-7 and 21-22, as follows:
DataOutputStream output = new DataOutputStream(
new BufferedOutputStream(new
FileOutputStream(“temp.dat”));
DataInputStream input = new DataInputStream(
new BufferedInputStream(new
FileInputStream(“temp.dat”));
Introduction to Java Y.Daniel Liang
49
Case Studies: Copy File
This case study develops a program that copies files. The user needs
to provide a source file and a target file as command-line arguments
using the following command:
java Copy source target
The program copies a source file to a target file and displays the
number of bytes in the file. If the source does not exist, tell the user
the file is not found. If the target file already exists, tell the user the
file already exists.
Introduction to Java Y.Daniel Liang
50
50
Case Studies: Copy File
The program uses the File class to check whether the source file
and the target file exist.
The program copies a Java source file to an identical Java file
Copy
Introduction to Java Y.Daniel Liang
Run
51
51
Optional
Object I/O
DataInputStream/DataOutputStream enables you to perform I/O for
objects in addition to primitive type values and strings.
ObjectInputStream/ObjectOutputStream enables you to perform I/O
for objects in addition for primitive type values and strings.
FileInputStream
DataInputStream
InputStream
FilterInputStream
BufferedInputStream
ObjectInputStream
Object
OutputStream
FileOutputStream
BufferedOutputStream
FilterOutputStream
DataOutputStream
ObjectOutputStream
PrintStream
Introduction to Java Y.Daniel Liang
52
ObjectInputStream
ObjectInputStream extends InputStream and
implements ObjectInput and ObjectStreamConstants.
java.io.InputStream
ObjectStreamConstants
java.io.DataInput
java.io.ObjectInputStream
+ObjectInputStream(in: InputStream)
java.io.ObjectInput
+readObject(): Object
Introduction to Java Y.Daniel Liang
Reads an object.
53
ObjectOutputStream
ObjectOutputStream extends OutputStream and
implements ObjectOutput and ObjectStreamConstants.
ObjectStreamConstants
java.io.OutputStream
java.io.DataOutput
java.io.ObjectOutput
java.io.ObjectOutputStream
+ObjectOutputStream(out: OutputStream)
+writeObject(o: Object): void Writes an object.
Introduction to Java Y.Daniel Liang
54
Using Object Streams
You may wrap an ObjectInputStream/ObjectOutputStream on any
InputStream/OutputStream using the following constructors:
// Create an ObjectInputStream
public ObjectInputStream(InputStream in)
// Create an ObjectOutputStream
public ObjectOutputStream(OutputStream out)
TestObjectOutputStream
Run
TestObjectInputStream
Run
Introduction to Java Y.Daniel Liang
55
Object Streams
The ObjectInputStream class can save entire object out to a
disk, and the C class can read them back in.
Objects are saved in binary format; therefore, you use streams
and not writers.
For example, you can write a Bank Account object to a file:
BankAccount bk = new …;
ObjectOutputStream out = new ObjectOutputStream (
new FileOutputStream(“bank.dat”));
Out.writeObject(bk);
Introduction to Java Y.Daniel Liang
56
Object Streams
Use Object streams to save and restore all instance fields of an
object automatically.
When reading the object back in, you use the readObject
method of the ObjectInputStream class. That method returns
an Object reference, so you need to remember the types of the
objects that you saved and use a cast:
ObjectInputStream in = new ObjectInputStream (
new FileInputStream(“bank.dat”));
BankAccount bk = (BankAccount) in.readObject( );
The readObject method can throw a ClassNotFoundExceptionit is a checked exception, so you need to catch or declare it.
Introduction to Java Y.Daniel Liang
57
The Serializable Interface
Not all objects can be written to an output stream. Objects that can be
written to an object stream is said to be serializable. A serializable
object is an instance of the java.io.Serializable interface. So the class
of a serializable object must implement Serializable.
The Serializable interface is a marker interface. It has no methods, so
you don't need to add additional code in your class that implements
Serializable.
public MyClass implements Serializable{
// Definition of the class
}
Implementing this interface enables the Java serialization mechanism
to automate the process of storing the objects and arrays.
Introduction to Java Y.Daniel Liang
58
The transient Keyword
If an object is an instance of Serializable, but it contains
non-serializable instance data fields, can the object be
serialized?
The answer is no.
To enable the object to be serialized, you can use the
transient keyword to mark these data fields to tell the JVM
to ignore these fields when writing the object to an object
stream.
Introduction to Java Y.Daniel Liang
59
The transient Keyword, cont.
Consider the following class:
public class Foo implements java.io.Serializable {
private int v1;
private static double v2;
private transient A v3 = new A();
}
class A { } // A is not serializable
When an object of the Foo class is serialized, only variable v1 is
serialized.
Variable v2 is not serialized because it is a static variable, and
variable v3 is not serialized because it is marked transient. If v3 were
not marked transient, a java.io.NotSerializableException would occur.
Introduction to Java Y.Daniel Liang
60
Serializing Arrays
An array is serializable if all its elements are serializable.
So an entire array can be saved using writeObject into a file
and later restored using readObject. Listing 16.12 stores an
array of five int values an array of three strings, and an
array of two JButton objects, and reads them back to
display on the console. Note : java.io.File implements
Comparable and Serializable
TestObjectStreamForArray
Introduction to Java Y.Daniel Liang
Run
61
More about the Serializable Interface
The process of saving objects to a stream is called serialization because
each object is assigned a serial number on the stream. If the same object
is saved twice, only the serial number is written out the second time.
When the objects are read back in, duplicate serial numbers are restored
as reference to the same object.
Why don’t all classes implement Serializable?
For security reasons, some programmers may not want to serialize
classes with confidential contents. Once a class is serializable, anyone
can write its objects to disk and analyze the disk file.
There are also some classes that contain values that are meaningless once
a program exists, such as operating–system-specific font descriptors.
These values should not be serialized.
Introduction to Java Y.Daniel Liang
62
Random Access Files
All of the streams you have used so far are known as
read-only or write-only streams.
The external files of these streams are sequential files that
cannot be updated without creating a new file.
It is often necessary to modify files or to insert new
records into files.
Java provides the RandomAccessFile class to allow a file
to be read from and writen to at random locations.
Introduction to Java Y.Daniel Liang
63
RandomAccessFile
DataInput
DataInput
java.io.RandomAccessFile
+RandomAccessFile(file: File, mode:
String)
Creates a RandomAccessFile stream with the specified File object and
mode.
+RandomAccessFile(name: String,
mode: String)
Creates a RandomAccessFile stream with the specified file name
string and mode.
+close(): void
Closes the stream and releases the resource associated with the stream.
+getFilePointer(): long
Returns the offset, in bytes, from the beginning of the file to where the
next read or write occurs.
+length(): long
Returns the length of this file.
+read(): int
Reads a byte of data from this file and returns –1 an the end of stream.
+read(b: byte[]): int
Reads up to b.length bytes of data from this file into an array of bytes.
+read(b: byte[], off: int, len: int) : int
Reads up to len bytes of data from this file into an array of bytes.
+seek(long pos): void
Sets the offset (in bytes specified in pos) from the beginning of the
stream to where the next read or write occurs.
+setLength(newLength: long): void
Sets a new length of this file.
+skipBytes(int n): int
Skips over n bytes of input discarding the skipped bytes.
+write(b: byte[]): void
+write(byte b[], int off, int len)
Writes b.length bytes from the specified byte array to this file, starting
at the current file pointer.
+write(b: byte[], off: int, len: int):
void
Writes len bytes from the specified byte array starting at offset off to
this file.
Introduction to Java Y.Daniel Liang
64