| 1.Write a program to take a number from user and display whether it is perfect number |
// Perfect Number
import java.util.Scanner;
public class PerfectNumber {
public static void main(String[] args) {
// take numbers from user
Scanner s = new Scanner(System.in);
int num = s.nextInt();
int sum = 0;
for ( int i = 1; i <= num/2 ; i ++) {
if ( num % i == 0 ) {
sum += i;
}
}
if ( sum == num)
System.out.println("Perfect Number");
else
System.out.println("Not Perfect Number");
}
}
|
| 2.Accept ten numbers from user and display the largest of the given numbers |
// Accept ten numbers from user and display the largest of the given numbers.
import java.util.Scanner;
public class LargestNumber {
public static void main(String[] args) {
// take numbers from user
Scanner s = new Scanner(System.in);
int num, largest = 0;
for ( int i = 1; i <= 10 ;i ++) {
System.out.print("Enter a number : ");
num = s.nextInt();
if ( num > largest)
largest = num;
}
System.out.println("Largest Number : " + largest);
}
}
|
| 3. Accept two numbers and display the GCD of the numbers |
// Accept two numbers and display the GCD of the numbers
import java.util.Scanner;
public class GCD {
public static void main(String[] args) {
// take numbers from user
Scanner s = new Scanner(System.in);
int first = s.nextInt();
int second = s.nextInt();
int i = first < second ? first : second;
for ( ; i > 0 ; i --) {
if ( first % i == 0 && second % i == 0) {
System.out.println("GCD = " + i);
break;
}
}
}
}
|
| 4. Display first 10 Fibnoacci numbers |
// display Fibonacci series
public class Fibonacci {
public static void main(String[] args) {
int first = 1,second = 1, result;
System.out.println(first);
System.out.println(second);
for ( int i = 3; i <= 10 ; i ++) {
result = first + second;
System.out.println( result );
first = second;
second = result;
} // for
} // end of main
}
|
| 5. Accept two numbers on command line and raise base (first number) to power (second number). |
// Accept two numbers on command line and raise base (first number) to power (second number).
public class Power {
public static void main(String[] args) {
int base = Integer.parseInt( args[0]);
int power = Integer.parseInt( args[1]);
int result =1;
for ( int i = 1; i <= power ; i ++) {
result *= base;
}
System.out.printf("%d raised to %d = %d", base, power, result);
}
}
|
| 6. Accept a number and display its highest factor |
import java.util.Scanner;
public class HighestFactor {
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
System.out.print("Enter a number : ");
int num = s.nextInt();
for ( int i = num/2; i > 0 ; i --) {
if ( num % i == 0 ) {
System.out.printf("Highest Factor : %d\n",i);
break;
}
}
}
}
|
| 7. Accept a number and display the digits in the reverse order |
import java.util.Scanner;
public class ReverseDigits {
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
System.out.print("Enter a number : ");
int num = s.nextInt();
while( num != 0 )
{
System.out.print( num % 10);
num /= 10;
}
}
}
|
| 8. Create a function that takes a set of integers using varying length argument and returns the average of all the numbers. |
public class AverageOfNumbers {
public static void main(String[] args) {
System.out.println( average(10,20,45,33));
System.out.println( average(12,22,88));
}
public static int average(int ... numbers) {
int total = 0;
for(int n : numbers)
total += n;
return total / numbers.length;
}
}
|
| 9. Create an array of 10 elements. Read values from keyboard and fill the array. Interchange first 5 elements with last 5 elements and display the array. |
import java.util.Scanner;
public class InterchangeArray {
public static void main(String[] args) {
int a[] = new int[10];
Scanner s = new Scanner(System.in);
// read values from keyboard into array
for ( int i = 0 ; i < a.length ; i ++) {
System.out.printf("Enter a number for [%d] element :",i);
a[i] = s.nextInt();
}
System.out.println("Orginal Array");
printArray(a);
// interchange array
for ( int i = 0, j = a.length -1 ; i < a.length / 2; i ++, j --) {
int t = a[i];
a[i] = a[j];
a[j] = t;
}
System.out.println("Interchanged Array");
printArray(a);
}
public static void printArray(int [] a) {
for(int n : a) {
System.out.printf("%5d",n);
}
}
}
|
| 10. Display palindrome numbers in the range 100 to 1000 |
public class PalindromeNumbers {
public static void main(String[] args) {
for ( int i = 100; i <= 1000; i ++) {
int n = i, rn = 0;
while (n > 0 ) {
int d = n % 10; // get right most digit
rn = rn * 10 + d;
n /= 10; // remove right most digit
}
if ( i == rn )
System.out.println(i);
}
}
}
|
| Accept a file and count number of words in the given file. |
// counts number of words assuming words are separated with only one space
import java.io.FileReader;
import java.util.Scanner;
public class CountWords {
public static void main(String[] args) {
System.out.print("Enter a filename : ");
Scanner s = new Scanner(System.in);
String filename = s.nextLine();
try (FileReader fr = new FileReader(filename)) {
int nowords = 0;
int ch = fr.read();
while (ch != -1) {
if (ch == '\n' || ch == ' ') {
nowords++;
}
ch = fr.read();
}
System.out.printf("No. of words = %d\n", nowords);
} catch (Exception ex) {
System.out.println(ex.getMessage());
}
}
}
// A better version of the exercise is given with BufferedReader and split() method of String
import java.io.BufferedReader;
import java.io.FileReader;
import java.util.Scanner;
public class CountWordsInFile {
public static void main(String[] args) {
System.out.print("Enter a filename : ");
Scanner s = new Scanner(System.in);
String filename = s.nextLine();
try (FileReader fr = new FileReader(filename);
BufferedReader br = new BufferedReader(fr)) {
String line = br.readLine();
int nowords = 0;
while (line != null) {
String[] words = line.split(" ");
// trim words to count only words with non-space characters
for (String w : words) {
if (w.trim().length() > 0) {
nowords++;
}
}
line = br.readLine();
}
System.out.printf("No. of words = %d\n", nowords);
} catch (Exception ex) {
System.out.println(ex.getMessage());
}
}
}
|
| Accept a filename, a string and display all lines in the file that contain the given string |
import java.io.BufferedReader;
import java.io.FileReader;
import java.util.Scanner;
public class DisplayLinesWithString {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("Enter a filename : ");
String filename = scanner.nextLine();
System.out.print("Enter a string : ");
String searchstring = scanner.nextLine();
try ( FileReader fr = new FileReader(filename);
BufferedReader br = new BufferedReader(fr)) {
String line = br.readLine();
while( line != null) {
if ( line.contains(searchstring))
System.out.println(line);
line = br.readLine();
}
}
catch(Exception ex) {
System.out.println(ex.getMessage());
}
}
}
|
| Display only non-blank lines of the given file along with line numbers. |
import java.io.BufferedReader;
import java.io.FileReader;
import java.util.Scanner;
public class NonblankLinesWithLineNumbers {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("Enter a filename : ");
String filename = scanner.nextLine();
try (FileReader fr = new FileReader(filename);
BufferedReader br = new BufferedReader(fr)) {
String line = br.readLine();
int lineno = 1;
while (line != null) {
if (line.trim().length() > 0) {
System.out.printf("%5d:%s\n", lineno, line);
}
line = br.readLine();
lineno ++;
}
} catch (Exception ex) {
System.out.println(ex.getMessage());
}
}
}
|
| Accept path from user and display list of files from the given path |
import java.io.*;
import java.util.Scanner;
public class FileList
{
public static void main(String args[])
{
Scanner s = new Scanner(System.in);
System.out.println("Enter directory name :");
String dir = s.nextLine();
File path = new File(dir);
if (! path.isDirectory())
{
System.out.println( dir + " is not a directory");
return;
}
File list [] = path.listFiles();
for ( File f : list)
{
if ( f.isDirectory())
System.out.println(f.getName() + "\t" + "[DIR]");
else
System.out.println( f.getName() + "\t" + f.length());
} // end of for loop
} // end of main
} // end of class
|
| Accept file name from user and display contents of file in reverse order- first line last. |
import java.io.BufferedReader;
import java.io.FileReader;
import java.util.Scanner;
import java.util.Stack;
public class ReverseFile {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("Enter a filename : ");
String filename = scanner.nextLine();
Stack<String> lines= new Stack();
try (FileReader fr = new FileReader(filename);
BufferedReader br = new BufferedReader(fr)) {
String line = br.readLine();
while (line != null) {
lines.push(line);
line = br.readLine();
}
// display stack
while(! lines.isEmpty())
System.out.println( lines.pop());
} catch (Exception ex) {
System.out.println(ex.getMessage());
}
}
}
|
| Question No. | Correct Answer |
| 1 | c |
| 2 | d |
| 3 | d |
| 4 | c |
| 5 | a |
| 6 | c |
| 7 | c |
| 8 | a |
| 9 | d |
| 10 | d |
| 11 | a |
| 12 | c |
| 13 | a |
| 14 | c |
| 15 | d |
| 16 | c |
| 17 | c |
| 18 | c |
| 19 | d |
| 20 | c |
| 21 | d |
| 22 | b |
| 23 | c |
| 24 | b |
| 25 | d |
| 26 | a |
| 27 | d |
| 28 | c |
| 29 | c |
| 30 | b |
| 31 | b |
| 32 | c |
| 33 | a |
| 34 | c |
| 35 | d |
| 36 | b |
| 37 | d |
| 38 | b |
| 39 | b |
| 40 | a |
| 41 | d |
| 42 | a |
| 43 | a |
| 44 | b |
| 45 | a |
| 46 | c |
| 47 | a |
| 48 | d |
| 49 | a |
| 50 | c |