import java.io.*;
import java.util.*;
import javax.swing.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;
public class Client {
JTextArea incoming;
JTextField outgoing;
JButton sendbutton;
BufferedReader reader;
PrintWriter writer;
Socket sock;
public void go(){
JFrame frame = new JFrame("Client");
JPanel mainpanel = new JPanel();
incoming = new JTextArea(15,50);
incoming.setLineWrap(true);
incoming.setWrapStyleWord(true);
incoming.setEditable(false);
JScrollPane qScroller = new JScrollPane(incoming);
qScroller.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
qScroller.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS);
outgoing = new JTextField(20);
sendbutton = new JButton("Send");
sendbutton.addActionListener(new SendButtonListener());
mainpanel.add(qScroller);
mainpanel.add(outgoing);
mainpanel.add(sendbutton);
setUpNetworking();
Thread readerThread = new Thread(new IncomingReader());
readerThread.start();
frame.getContentPane().add(BorderLayout.CENTER, mainpanel);
frame.setSize(400, 400);
frame.setVisible(true);
}
public static void main(String[] args){
Client client = new Client();
client.go();
}
private void setUpNetworking(){
try{
sock = new Socket("127.0.0.1", 5000);
InputStreamReader streamReader = new InputStreamReader(sock.getInputStream());
reader = new BufferedReader(streamReader);
writer = new PrintWriter(sock.getOutputStream());
System.out.println("Networking established!!");
}catch(IOException e){
e.printStackTrace();
}
}
public class SendButtonListener implements ActionListener{
public void actionPerformed(ActionEvent e){
try{
writer.println(outgoing.getText());
writer.flush();
}catch(Exception ex){
ex.printStackTrace();
}
outgoing.setText("");
outgoing.requestFocus();
}
}
public class IncomingReader implements Runnable{
public void run(){
String message;
try{
while((message = reader.readLine()) != null){
System.out.println("read" + message);
incoming.append(message + "\n");
//incoming.setText(message + "\n");
}
}catch(Exception e){
e.printStackTrace();
}
}
}
}
BufferedReader
Data Structures using Java Part 1: String objects and I/O in Java
Objects and methods
———————–
String s1; //declare a String variable s1 = new String(); // assign it a value String s2 = new String(); // both the steps combined s1 = "Hello"; // assign the value into the object s1 s2 = s1; // s1 and s2 points to the same object, same value s2 = new String(s1); // creates a new String object and copies the value of s1 into s2
The 3 String constructors
—————————-
1. new String() constructs a empty string, ie no characters
String s1; //declare a String variable s1 = new String(); // assign it a value String s2 = new String(); // both the steps combined
2. Stick something in quotes.
s1 = "Hello"; // assign the value into the object s1
3. Takes a parameter.
s2 = new String(s1); // creates a new String object and copies the value of s1 into s2; the constructor parameter is s1
NOTE: Constructors always have the name of the class
String Methods
—————–
1. Conversion into uppercase
s2 = s1.toUpperCase();
2. To concatenate two Strings
String name = s2.concat(" says hello!");
String say = "*".concat(name).concat("*");
Unlike in C, in Java String objects are immutable, ie their contants never change.
Java I/O Classes
——————
Objects in System classes for interacting with user
1. System.out
a PrintStream object that outputs to the screen.
2. System.in
a InputStrem object thats reads stuff from the keyboard.
3.readLine method
is defined on a BufferedReader objectm is used to read a whole line.
How do we construct a BufferReader?
With a InputStreamReader.
How do we construct a InputStreamReader?
We need an InputStream.
How do we construct a InputStream?
System.in is one.
The InputStream objects, their job is to read raw data from the keyboard. An unformatted bit stream. The InputStreamReader object takes the raw data and compose them into characters. Java usually uses unicode 2 byte long characters. The ufferedReader object takes the raw characters and converts them into text. This is done in 3 steps for modularity reasons.
import java.io.*;
class SimpleIO{
public static void main( String args[] ) throws Exception{
BufferedReader keyboard = new BufferedReader(
new InputStreamReader(System.in)
);
System.out.println(keyboard.readLine());
}
}
To use the Java library, other than java.lang, you need to import that library. You need to import the java.io for the ISR and the BR. The java program always begins with the “main” method.
LinuxJunkies 