Closed Java Sample Programs

Java Sample Programs
Fall 2002



A Revised Version of Hello World
import java.io.*;
class MyFirstProgram {
/** Print a hello message */
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 {
// Print out the Fibonacci sequence for values < 50
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; // new hi
lo = hi - lo; /* new lo is (sum - old lo)
i.e., the old hi */
}
}


A Java Class
class Point {
public double x, y;
public static Point origin = new Point(0,0);
// This always refers to an object at (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 {
/** Return the value associated with the name, or
* null if there is no such value */
Object find(String name);
}

void processValues(String[] names, Lookup table) {
for (int i = 0; i ! names.length; i++) {
Object value = table.find(names);
if (value != null)
processValue(names, 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.equals(name))
return Values;
}
return null; // not found
}
// ...
}


Creating Threads in Java
public class PingPONG extends Thread {
private String word; // What word to print
private int delay; // how long to pause
public PingPONG(String whatToSay, int delayTime) {
word = whatToSay;
delay = delayTime;
}
public void run() {
try {
for (; {
System.out.print(word + " ");
sleep(delay); // wait until next time
}
} catch (InterruptedException e) {
return; // end this thread;
}
}
public static void main(String[] args) {
new PingPONG("Ping", 33).start(); // 1/30 second
new PingPONG("PONG",100).start(); // 1/10 second
}
}


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;
}
}

/** make all elements in the array non-negative */
public static void abs(int[] values) {
synchronized (values) {
for (int i = 0; i < values.length; i++) {
if (values < 0)
values = -values;
}
}
}


HTML Applet Tags
<APPLETT CODE=classFileName // .class HEIGHT=height // in pixels WIDTH=width? // Only these 3 are required. [CODEBASE=classFileDirectory] // if different from the HTML file [NAME=appletName] // so that applets can refer to each other [ALT=alternateText] [ALIGN=alignment] [HSPACE=spaceInPixels] [VSPACE=spaceInPixels] [<PARAM NAME=parameterName VALUE=parameterValue>] [<PARAM...>] </APPLET>

thanks dito makakatulong sa module ko ts

welcome po

nice para sa newbie mag code

Thanks for sharing