6. Java basic I/O 2. Files

Сентябрь 7, 2022

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6. Java basic I/O 2. Files

Содержание

2. Write to a Text File Example import java.io.*; public void Write(String fileId){ PrintStream outF = null;
3. Home Exercise: Create Deposit Report Modify 512SortDepo project to get deposit report in a text file.
4. Read from a Text File Example public void Read(String fileId){ BufferedReader inF = null; try{ inF
5. Random Access Files Random access files permit nonsequential, or random, access to a file's contents To
6. Random Access File Example File f = new File("test.txt"); FileChannel fc = (FileChannel.open(f, READ, WRITE)); fc.position(10);
7. What Is a Path? Java 7 A file is identified by its path through the file
8. Relative and Absolute Path A path is either relative or absolute. The latter contains the root
9. Creating a Path A Path instance contains the information used to specify the location of a
10. Path Operations Retrieving Information About a Path Converting a Path Joining Two Paths Creating a Path
11. The File Class The Files class is the other primary entrypoint of the java.nio.file package You
12. Some File Operations Verifying the Existence of a File or Directory (exists, notExists) Checking File Accessibility
14. Скачать презентацию

Слайд 2

Write to a Text File Example
import java.io.*;
public void Write(String fileId){
PrintStream

outF = null;
try{ outF = new PrintStream(fileId);
outF.println(”This is a test record”); }
catch(IOException e){…processing code }
finally{ if (outF != null) outF.close(); }
}

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Слайд 3

Home Exercise: Create Deposit Report
Modify 512SortDepo project to get deposit report

in a text file.

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Слайд 4

Read from a Text File Example
public void Read(String fileId){
BufferedReader inF

= null;
try{ inF = new BufferedReader(new FileReader(fileId));
while (txt = inF.readLine() != null){
// code for processing txt
}
}
catch(IOException e) { … processing code }
finally{ if (inF != null) inF.close(); }
}

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Слайд 5

Random Access Files
Random access files permit nonsequential, or random, access to

a file's contents
To access a file randomly, you:
open the file
seek a particular location
read from or write to that file

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Слайд 6

Random Access File Example
File f = new File("test.txt");
FileChannel fc = (FileChannel.open(f,

READ, WRITE));
fc.position(10);
ByteBuffer copy = ByteBuffer.allocate(12);
do {
nread = fc.read(copy);
// processing copy
}
while (nread != -1 && copy.hasRemaining());
fc.close();

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Слайд 7

What Is a Path?
Java 7
A file is identified by its path

through the file system, beginning from the root node
The Path class is a programmatic representation of a path in the file system
A Path object contains the file name and directory list used to construct the path

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Слайд 8

Relative and Absolute Path
A path is either relative or absolute.
The

latter contains the root element.
A relative path needs to be combined with another path in order to access a file.
The character used to separate the directory names (also called the delimiter) is specific to the file system
It is used to examine, locate, and manipulate files

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Слайд 9

Creating a Path
A Path instance contains the information used to specify

the location of a file or directory
A root element or a file name might be included, but neither are required
Path p1 = Paths.get("/tmp/foo");
Path p2 = Paths.get(args[0]);
Path p3 = Paths.get(URI.create("file:///Users/joe/FileTest.java"));

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Слайд 10

Path Operations
Retrieving Information About a Path
Converting a Path
Joining Two Paths
Creating a

Path Between Two Paths
Comparing Two Paths

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Слайд 11

The File Class
The Files class is the other primary entrypoint of

the java.nio.file package
You can get some functionality of Path class from the File class in pre-JDK7.

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Слайд 12

Some File Operations
Verifying the Existence of a File or Directory (exists,

notExists)
Checking File Accessibility (isReadable, isWritable, isExecutable)
Copying / Moving a File or Directory (copy, move)
Creating and Reading Directories (createDirectory, newDirectoryStream)

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6. Java basic I/O 2. Files

Содержание

Write to a Text File Exampleimport java.io.*;public void Write(String fileId){ PrintStream

Home Exercise: Create Deposit ReportModify 512SortDepo project to get deposit report

Read from a Text File Examplepublic void Read(String fileId){ BufferedReader inF

Random Access FilesRandom access files permit nonsequential, or random, access to

Random Access File Example File f = new File("test.txt"); FileChannel fc = (FileChannel.open(f,

What Is a Path?Java 7A file is identified by its path

Relative and Absolute PathA path is either relative or absolute. The

Creating a PathA Path instance contains the information used to specify

Path OperationsRetrieving Information About a PathConverting a PathJoining Two PathsCreating a

The File ClassThe Files class is the other primary entrypoint of

Some File OperationsVerifying the Existence of a File or Directory (exists,

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Write to a Text File Example
import java.io.*;
public void Write(String fileId){
PrintStream

Home Exercise: Create Deposit Report
Modify 512SortDepo project to get deposit report

Read from a Text File Example
public void Read(String fileId){
BufferedReader inF

Random Access Files
Random access files permit nonsequential, or random, access to

Random Access File Example
File f = new File("test.txt");
FileChannel fc = (FileChannel.open(f,

What Is a Path?
Java 7
A file is identified by its path

Relative and Absolute Path
A path is either relative or absolute.
The

Creating a Path
A Path instance contains the information used to specify

Path Operations
Retrieving Information About a Path
Converting a Path
Joining Two Paths
Creating a

The File Class
The Files class is the other primary entrypoint of

Some File Operations
Verifying the Existence of a File or Directory (exists,