1.
Write an applet
program to change the background color
import java.awt.*;
public class color5 extends java.applet.Applet {
public void init() {
Color
lightOrange = new Color(230, 220, 0);
setBackground(lightOrange);
}
public void
paint(Graphics screen) {
Color darkRed
= new Color(235, 50, 50);
screen.setColor(darkRed);
screen.drawString("Welcome", 5, 50);
Font
currentFont = new Font("TimesRoman", Font.PLAIN, 20);
screen.setFont(currentFont);
screen.drawString("Welcome", 5, 150);
currentFont =
new Font("TimesRoman", Font.ITALIC, 40);
screen.setFont(currentFont);
screen.drawString("Welcome", 5, 250);
}
}
2.
What
is exception? Write a java program to implement try, catch nested try, throw
and throws method.
A Java exception is an
object that describes an exceptional (that is, error) condition that has
occurred in a piece of code. When an exceptional condition arises, an object
representing that exception is created and thrown in the method that caused the
error. That method may choose to handle the exception itself, or pass it on.
Either way, at some point, the exception is caught and processed.
i) Nested try block
class NestedTry
{
public static void main(String args[])
{
try
{
int num = args.length;
try
{
int numValue = Integer.parseInt(args[0]);
System.out.println("The square is " + numValue * numValue);
}
catch(NumberFormatException nb)
{
System.out.println("Not a number! ");
}
}
catch(ArrayIndexOutOfBoundsException ne)
{
System.out.println("No arguments given! ");
}
}
}
ii) try –catch block
mport java.io.*;
public class ExcepTest{
public static void main(String args[]){
try{
int a[] = new int[2];
System.out.println("Access element three :" + a[3]);
}catch(ArrayIndexOutOfBoundsException e){
System.out.println("Exception thrown :" + e);
}
System.out.println("Out of the block");
}
}
iii) throws & thriw block
import java.io.*;
public class className
{
public void deposit(double amount) throws RemoteException
{
// Method implementation
throw new RemoteException();
}
//Remainder of class definition
}
3.
i)Write
a small applet program to draw lines.
ii) Write asmall applet program to draw
rectangles.
iii)Write a small applet program to draw
ellipses and circles.
iv)Write a small applet program to draw arcs.
v)Write a small applet program to draw
polygons.
Sol:
i)
import java.awt.*;
import java.applet.*;
public class line1 extends Applet
{
public
void paint(Graphics g)
{
g.drawLine(40,25,250,180);
}
}
|
ii)
import java.awt.*;
import java.applet.*;
public class rect extends Applet
{
public
void paint(Graphics g)
{
g.drawRect(10,10,60,50);
}
}
|
iii)
import java.awt.*;
import java.applet.*;
public class circle_ellipse extends Applet
{
public
void paint(Graphics g)
{
g.drawOval(10,10,50,50);//circle
g.drawOval(190,10,90,30);// ellipse
}
}
|
iv) import java.awt.*;
import java.applet.*;
public class arcs extends Applet
{
public
void paint(Graphics g)
{
g.drawArc(10,100,70,80,0,175);
}
}
|
v)
import java.awt.*;
import java.applet.*;
public class polygon extends Applet
{
public void
paint(Graphics g)
{
int xpoints[]={30,200,30,200,30};
int ypoints[]={30,30,200,200,30};
int num=5;
g.drawPolygon(xpoints,ypoints,num);
}
}
4.
What are different types of controls
supported by abstract window toolkit? Explain at least.
Sol:
The Abstract Windowing Toolkit
(AWT), or "another windowing toolkit," as some people affectionately
call it, provides a large collection of classes for building graphical user
interfaces in Java. With AWT, you can create windows, draw, work with images,
and use components like buttons, scrollbars, and pull-down menus in a platform
independant way. The java.awt
package contains the AWT GUI classes. The java.awt.image package provides some
additional tools for working with images.
Structure of the AWT
The structure of the AWT is rather simple: Components
are added to and then laid out by layoutmanagers in Containers.
We have a variety of event handling, menu, fonts, graphics classes in addition
to those two, but they'll be only briefly discussed here.
Nothing prevents us from using threads, audio, I/O, networking classes
alongside the AWT. The AWT by itself is rather bare and empty. Imagine a text
editor that couldn't save! As a side note, the AWT can be used in a stand-alone
Java application or in an applet that is embedded within a HTML document. The AWT hierarchy
Classes:
·
BorderLayout
·
CardLayout
·
CheckboxGroup
·
Color
·
Component
o
Button
o
Canvas
o
Checkbox
o
Choice
o
Container
§
Panel
§
Window
§
Dialog
§
Frame
o
Label
o
List
o
Scrollbar
o
TextCompoment
§
TextArea
§
TextField
·
Dimension
·
Event
·
FileDialog
·
FlowLayout
·
Font
·
FontMetrics
·
Graphics
·
GridLayout
·
GridBagConstraints
·
GridBagLayout
·
Image
·
Insets
·
MediaTracker
·
MenuComponent
o
MenuBar
o
MenuItem
§
CheckboxMenuItem
§
Menu
·
Point
·
Polygon
·
Rectangle
·
Toolkit
5.
What
do you mean by command line argument?
A Java application can accept any number of
arguments from the command line. This allows the user to specify configuration
information when the application is launched.
The user enters command-line arguments when
invoking the application and specifies them after the name of the class to be
run. For example, suppose a Java application called
Sort sorts
lines in a file. To sort the data in a file named friends.txt, a user would
enter:java Sort friends.txt
When an application is launched, the runtime
system passes the command-line arguments to the application's main method via
an array of
Strings.
In the previous example, the command-line arguments passed to the Sort
application in an array that contains a single String: "friends.txt".Echoing Command-Line Arguments
The
Echo example displays each of its
command-line arguments on a line by itself:
public class Echo {
public static void main (String[] args) {
for (String s: args) {
System.out.println(s);
}
}
}
The following example shows how a user might run
Echo. User
input is in italics.java Echo Drink Hot Java
Drink
Hot
Java
Note that the application displays each word —
Drink, Hot, and Java — on a
line by itself. This is because the space character separates command-line
arguments. To have Drink,
Hot,
and Java
interpreted as a single argument, the user would join them by enclosing them
within quotation marks.java Echo "Drink Hot Java"
Drink Hot Java
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