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Computer programming- II (CS 2300)
Java Lab Exercise #01
Lab Session - #01
Java fundamental
Basic Input/Output
Evaluation:
Student Name & Number
Instructor: Maha & dhekra
Date:
Q1: Which of the following is a correct Java identifier:
SS
N1
a$total2
D_D
F TR
R.ER
2UYR
#FER
public
a-total
Num of hours totalGrade
Score_a
int
double
import
Sara’sBook 3rd
s-3
G-R-Y
St8first
sa$
_ds
3Sum
class
$mo
Q2: Which of the following is correctly formed constant (or literal) of type integer?
1 45
4.
12.3
34
‘8’
“9”
-6
12,5
Q3: Which of the following is correctly formed constant (or literal) of type char?
‘ab’
‘a’
“A”
‘3’
“5”
‘?’
“%”
z
Q4: Which of the following is correctly formed constant (or literal) of type double?
5.32
5
4.
1,6
-7.5
“4.77”
Q5: Decide if these identifiers follow the naming conventions or not, and if not try to rewrite
them, so they follow the conventions:
identifiers
correction
class hello
class Hello
int R
int r
char c
class Test
int markTotal
final int numOfMonth = 12
final int NUM_OF_MONTH = 12
final double RENT_RATE = 10.5
double scoreaverage
Double scoreAverage
Q6: Correct the errors
byte x = 130; // short x = 130; OR int x = 130; OR long x = 130;
short y = 40000; // int y = 40000 OR long y = 40000;
int z = 3000000000; // long z = 3000000000L;
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Computer programming- II (CS 2300)
Lab Session - #01
Q7: Which of the following variable declaration are correct? If a variable declaration is not
correct, give the reason(s) and provide the correct variable declaration.
n = 12 ;// not correct because the data type is missing int n = 12;
char letter = ;// not correct because there is no character literal or variable at the right side of = ,
char letter = ‘r’;
int one = 5, two; // correct
double x, y, z ; // correct
Q8: Write Java statements that accomplish the following.
a. Declare int variables x and y.
int x, y;
b. Initialize an int variable x to 10 and a char variable ch to 'B'.
int x = 10;
char ch = ‘B’;
c. Update the value of an int variable x by adding 5 to it.
x = x + 5;
d. Declare and initialize a double variable payRate to 12.50.
double payRate = 12.50;
e. Copy the value of an int variable firstNum into an int variable tempNum.
tempNum = firstNum;
f. Swap the contents of the int variables x and y. (Declare additional variables, if necessary.)
int temp = x;
x = y;
y = temp;
g. Declare a char variable grade and set the value of grade to 'A'.
char grade = ‘A’;
h. Declare int variables to store four integers.
int x=1, y=2, z=3, w=4 ;
Q9 .Find the errors in the following programs: (Each segment has 4 errors)
a. public static void main( String args[] ) {
int x, n, m=1 ,y+1 ; wrong declaration for y+1
m-2 = n; left side can’t be an expression
y = x + m; x has no value
System.out.println(" Sum is "+ y), ; not ,
}
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Computer programming- II (CS 2300)
Lab Session - #01
b. public class Errors
{
final int NUM=11;
public static void main( String args[] )
{
char ch = ‘m’;
int N = 3 : t; , not :
n = 5; n is not declared
NUM = N+3; NUM is constant, change is not allowed!!
System.out.println("ch=" + Ch+", NUM="+NUM )); ch not Ch
}
}
Q10. What is the output of the following program?
Program
// IO example
import java.util.Scanner;
public class IOExample
{
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
int i=3;
System.out.println("Java is a powerful programming language");
System.out.print("Please enter an integer number: ");
i = input.nextInt();
System.out.printf("%s%d","The number you entered is ", i);
System.out.printf("%s%d%s%d","and two times of ", i, " is ", i*2);
}
}
Output
Java is a powerful programming language
Please enter an integer number: 4
The number you entered is 4 and two times of 4 is 8
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Computer programming- II (CS 2300)
Lab Session - #01
Q11.What is output by the following program
Program
import javax.swing.JOptionPane;
public class AreaRectangle
{
public static void main(String[] args)
{
int length, width, area;
String string;
string = JOptionPane.showInputDialog(null, "Enter the length: ",
"Input", JOptionPane.INFORMATION_MESSAGE);
length = Integer.parseInt(string);
string = JOptionPane.showInputDialog(null, "Enter the width: ",
"Input", JOptionPane.INFORMATION_MESSAGE);
width = Integer.parseInt(string);
area = length*width;
JOptionPane.showMessageDialog(null, "Area = "+area, "Display Area",
JOptionPane.INFORMATION_MESSAGE);
}
}
Output
4
Computer programming- II (CS 2300)
Lab Session - #01
Q12. Write a simple java program to display “ Welcome to Java “ ?
Output
Welcome to java
Program
public class SimpleProgram
{
public static void main(String[] args)
{
System.out.println("Welcom to Java");
}
}
Q13. Write a program that reads two numbers and print the sum of two numbers ?
Output
Enter the first number: 5
Enter the second number: 3
The sum = 8
Program
import java.util.Scanner;
public class Sum
{
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
int num1,num2,sum;
System.out.print("Enter the first num:");
num1 = input.nextInt();
System.out.print("Enter the second num:");
num2 = input.nextInt();
sum=num1+num2;
System.out.println("Sum="+sum);
}
}
5