A Revised Version of Hello World
import java.io.*;
class MyFirstProgram
{
public static void main(String[]
args)
{
BufferedReader in = new BufferedReader(new
InputStreamReader(System.in));
String name = "Instructor";
System.out.print("Give your name: ");
try
{
name = in.readLine();
}
catch(Exception e)
{
System.out.println("Caught an exception!");
}
System.out.println("Hello "
+ name + "!");
}
}
A Java Program with Looping
class Fibonacci
{
public static void main(String[] args)
{
int lo = 1;
int hi = 1;
System.out.println(lo);
while (hi < 50)
{
System.out.print(hi);
hi
= lo + hi;
lo
= hi - lo;
}
}
A Java Class
class Point
{
public double x, y;
public static Point origin = new
Point(0,0);
Point(double x_value, double y_value)
{
x = x_value;
y = y_value;
}
public void clear()
{
this.x = 0;
this.y = 0;
}
public double distance(Point that)
{
double xDiff = x - that.x;
double yDiff = y - that.y;
return Math.sqrt(xDiff * xDiff + yDiff *
yDiff);
}
}
Extending a Class: Inheritance
class Pixel extends Point
{
Color
color;
public void clear()
{
super.clear();
color = null;
}
}
Interfaces
interface Lookup
{
Object find(String name);
}
void processValues(String[] names, Lookup
table)
{
for (int i = 0; i ! names.length; i++)
{
Object value = table.find(names[i]);
if (value != null)
processValue(names[i],
value);
}
}
class SimpleLookup implements Lookup
{
private String[] Names;
private Object[] Values;
public
Object find(String name)
{
for (int i = 0; i < Names.length; i++)
{
if (Names[i].equals(name))
return Values[i];
}
return null;
}
}
Creating Threads in Java
public class PingPONG extends Thread
{
private
String word;
private int delay;
public PingPONG(String whatToSay, int
delayTime)
{
word = whatToSay;
delay = delayTime;
}
public void run()
{
try
{
for (;;)
{
System.out.print(word + "
");
sleep(delay);
}
}
catch (InterruptedException e)
{
return;
}
}
public
static void main(String[] args)
{
new PingPONG("Ping", 33).start();
new PingPONG("PONG",100).start();
}
}
Two Synchronization Methods
class Account
{
private double balance;
Public Account(double initialDeposit)
{
balance = initialDeposit;
}
public
synchronized double getBalance()
{
return balance;
}
public
synchronized viod deposit(double amount)
{
balance += amont;
}
}
public static void abs(int[] values)
{
synchronized (values)
{
for (int i = 0; i < values.length; i++)
{
if (values[i] < 0)
values[i] = -values[i];
}
}
}
UseArgument.java
public class
UseArgument
{
public static void main(String[] args)
{
System.out.print("Hi, ");
System.out.print(args[0]);
System.out.println(". How are
you?");
}
}
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