PROGRAMOWANIE W SIECI INTERNET WYKŁAD

PROGRAMOWANIE
W SIECI INTERNET
WYKŁAD
Tworzenie pliku tymczasowego
import java.io.File;
import java.io.IOException;
import java.io.FileWriter;
class Main {
public static void main(String[] args) {
try {
File temp = File.createTempFile("jcl", ".out");
// Make sure it gets deleted when we're done
temp.deleteOnExit();
// Print out file name to see what we got
System.out.println(temp);
FileWriter fout = new FileWriter(temp);
for (int i = 0; i < 100; i++) {
fout.write("hello" + i);
}
fout.close();
System.out.println("Temp file size: " + temp.length());
} catch (IOException e) {
e.printStackTrace();
}
}
}
Pobranie ścieżki bezwzględnej
import java.io.File;
import java.io.IOException;
import java.io.File;
class Main {
public static void main(String[] args) {
//
System.out.println(new File("Main.java").getAbsoluteFile());
System.out.println(
new File("c:\\frontpage_webs\\", "Content").getAbsoluteFile());
// c:\frontpage_webs\Content
System.out.println(
new File("c:\\frontpage_webs", "Content").getAbsoluteFile());
// c:\frontpage_webs\Content
System.out.println(new File("\\tmp\\graphics").getAbsoluteFile());
// \tmp\graphics
//
}
}
Sprawdzanie czy dany plik jest ukryty
import java.io.*;
class Main {
public static void main(String[] args) {
//
System.out.println(new File("Main.java").isHidden());
System.out.println(new File(".").isHidden());
System.out.println(new File("..").isHidden());
System.out.println(new File(".out").isHidden());
System.out.println(new File("/tmp", ".").isHidden());
//
}
}
Wyświetlenie dysków
import java.io.*;
class Main {
public static void main(String[] args) {
//
File[] roots = File.listRoots();
if (roots == null) {
System.out.println("Cannot get
roots");
} else {
for (int i = 0; i < roots.length; i++) {
System.out.println(roots[i]);
}
}
//
}
}
Ustawienie „tylko do odczytu”
import java.io.*;
class Main {
public static void main(String[] args) {
if (args.length != 1) {
System.err.println("usage: java Main <filename>");
System.exit(-1);
}
if ((new File(args[0])).setReadOnly()) {
System.out.println("Set file to read-only mode");
} else {
System.out.println("Cannot set to read-only mode");
}
}
}
Konwersja ścieżki na adres URL
import java.io.*;
import java.net.*;
class Main {
public static void main(String[] args) {
//
try {
System.out.println(new File("Main.java").toURL());
System.out.println(new File("\\tmp", "Main.java").toURL());
System.out.println(new File("c:\\book\\sup1", "Main.java").toURL
());
} catch (MalformedURLException e) {
e.printStackTrace();
}
//
}
}
Wyświetlenie listy plików
import java.io.File;
import java.util.Date;
class Ls {
public static void printOne(File f) {
if (f.exists()) {
System.out.print(f.canRead() ? "r" : "-");
System.out.print(f.isDirectory() ? "d" : "-");
System.out.print(f.length());
System.out.print(f.canWrite() ? "w" : "-");
System.out.print('\t');
System.out.print('\t');
System.out.print(new Date(f.lastModified()));
System.out.print('\t');
} else {
System.out.print("\t\t\t\t\t");
}
System.out.println(f.getName());
}
public static void main(String[] args) {
if (args.length != 1) {
System.err.println("Usage: java Ls <filepath>");
System.exit(-1);
}
File f1 = new File(args[0]);
String[] ls;
int i;
for (ls = f1.list(), i = 0;
ls != null && i < ls.length;
printOne(new File(f1, ls[i])), i++);
}
}
import java.io.File;
Zmiana nazwy pliku
class Main {
public static void main(String[] args) {
if (args.length != 2) {
System.err.println("Usage: java Main <file1> <file2>");
System.exit(-1);
}
File f1 = new File(args[0]);
File f2 = new File(args[1]);
System.out.println("f1: " + f1.toString() + " " + f1.hashCode());
System.out.println("f2: " + f2.toString() + " " + f2.hashCode());
if (f1.equals(f2)) {
System.err.println("Cannot rename a file to itself");
System.exit(-1);
}
System.out.println(f1.getPath() +
(f1.renameTo(f2) ? " renamed to " : " could not be renamed to ") +
f2.getPath());
// check f1 and f2: their path and hash codes
System.out.println("f1: " + f1.toString() + " " + f1.hashCode());
System.out.println("f2: " + f2.toString() + " " + f2.hashCode());
}
}
DataOutputStream
import java.io.*;
class Main {
public static void main(String[] args) {
if (args.length != 1) {
System.err.println("Usage: java Main <output file>");
System.exit(-1);
}
FileOutputStream file_out;
DataOutputStream data_out;
try {
file_out = new FileOutputStream(args[0]);
data_out = new DataOutputStream(file_out);
char a = 'a';
byte b = 2;
String c = "abc";
short d = 4;
byte[] b2 = {'a', 'b', 'c'};
data_out.write(b);
data_out.write(b2, 0, b2.length);
data_out.writeBoolean(true);
data_out.writeChar(a);
data_out.writeBytes(c);
data_out.writeChars(c);
data_out.writeDouble(123.456);
data_out.writeFloat(123.456f);
data_out.writeInt(678);
data_out.writeLong(678l);
data_out.writeShort(d);
data_out.writeUTF(c);
data_out.writeUTF("abc\n");
data_out.write(b);
data_out.writeShort(d);
data_out.flush();
System.out.println("Size of file written: " + data_out.size());
data_out.close();
} catch (IOException e) {
System.out.println(e);
}
}
}
DataInputStream
import java.io.*;
class Main {
public static void main(String[] args) {
if (args.length != 1) {
System.err.println(
"Usage: java Main <output from DataOutput example>");
System.exit(-1);
}
FileInputStream file_in;
DataInputStream data_in;
try {
file_in = new FileInputStream(args[0]);
data_in = new DataInputStream(file_in);
System.out.println("Available: " + data_in.available());
byte b;
byte[] b2 = new byte[1];
b = data_in.readByte();
System.out.println("Byte: " + b);
data_in.read(b2);
System.out.println("Byte[0]: " + (char)b2[0]);
data_in.read(b2, 0, b2.length);
System.out.println("Byte[0]: " + (char)b2[0]);
int ub = data_in.readUnsignedByte();
System.out.println("Unsigned Byte: " + b);
System.out.println("Boolean: " + data_in.readBoolean());
char a = data_in.readChar();
System.out.println("Char: " + a);
byte[] b3 = new byte[3];
data_in.readFully(b3);
System.out.println("readFully: " + (char)b3[0] + (char)b3[1] +
(char)b3[2]);
data_in.skipBytes(6); // skip string 'abc'
double d1 = data_in.readDouble();
float f1 = data_in.readFloat();
int i = data_in.readInt();
long l = data_in.readLong();
short s = data_in.readShort();
String str = data_in.readUTF();
ub = data_in.readUnsignedByte();
int us = data_in.readUnsignedShort();
System.out.println("UTF String" + str);
} catch (IOException e) {
System.out.println(e);
}
}
}
Odczyt z pliku linia po linii
import java.io.*;
class New {
public static void main(String[] args) {
if (args.length == 0) {
System.err.println("java New <inputfile>");
System.exit(-1);
}
try {
BufferedReader in = new BufferedReader(new FileReader(args[0]));
String line;
while ((line=in.readLine()) != null) {
System.out.println(line);
}
in.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
Serializacja
import java.io.Serializable;
public class Class1 implements Serializable {
int field1;
String field2;
transient int field3;
public Class1() {
field1 = 10;
field2 = "a string";
field3 = -1;
}
}
import java.io.*;
Serializacja
class Main {
public static void main(String[] args) {
try {
// Write them out
FileOutputStream f = new FileOutputStream("Class1.ser");
ObjectOutput out = new ObjectOutputStream(f);
Class1 c = new Class1();
c.field3 = 15;
System.out.println("c1.field3 " + c.field3);
out.writeObject(c);
out.flush();
out.close();
// Read them back
FileInputStream f2 = new FileInputStream("Class1.ser");
ObjectInputStream in = new ObjectInputStream(f2);
Class1 cc1 = (Class1) in.readObject();
in.close();
System.out.println("c1.field1 " + cc1.field1);
System.out.println("c1.field2 " + cc1.field2);
System.out.println("c1.field3 " + cc1.field3);
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
}
Obiektowa baza danych
public void addObject(Object o)
public Object getObject(int id)
public void deleteObject(int id)
public void replaceObject(Object o)
public object[] getAllObjects()
public object[] getObjects(Object o)
Obiektowa baza danych
String nf1 = „file.main”;
String nf2 = „file.tmp”;
boolean w1;
File f1 = new File(nf1);
File f2 = new File(nf2);
if (f1.exists()) { w1 = true;} else { w1 = false;}
mtz advice = null;
Obiektowa baza danych
If (!w1) {
os01 = new FileOutputStream(nf1);
oos01 = new ObjectOutputStream(os01);
oos01.writeObject(obj);
oos01.flush();
oos01.close();
os01.flush();
os01.close();
} else {
Obiektowa baza danych
} else {
f1.renameTo(f2);
is02 = new FileInputStream(nf2);
ois02 = new ObjectInputStream(is02);
os01 = new FileOutputStream(nf1);
oos01 = new ObjectOutputStream(os01);
b = true;
while (b) {
try {
advice = (mtz)ois02.readObject();
codeOfMtz = advice.codeOfMtz;
} catch (Exception e) {
b = false;
}
if (b) oos01.writeObject(advice);
}
obj.codeOfMtz = codeOfMtz + 1;
oos01.writeObject(obj);
oos01.flush();
oos01.close();
os01.flush();
os01.close();
ois02.close();
is02.close();
f2.delete();
}