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2. Write a Java program to swap two variables.

3. Write a Java program to print a face.

4. Write a Java program to compare three numbers.
*NB: Accept all numbers from the keyboard.*

5. Write a Java program to check if a character is an alphabet using if-else.

6. Write a Java program to check if a number is even or odd.

7. Write a Java program to find the factorial of a number.

8. What will be the output for the following snippet of code?

```java
public class PrintPattern {
public static void main(String[] args) {
int rows = 5;
for (int i = 1; i <= rows; ++i) {
for (int j = 1; j <= i; ++j) {
System.out.print("* ");
}
System.out.println();
}
}
}
```

9. Write a Java program to check if a character is a vowel or consonant using if and switch statements.

10. Describe what happens if, in `helloWorld.java`, you omit:
a. `main`
b. `String`
c. `HelloWorld`
d. `System.out`

11. Write a Java program to calculate compound interest and simple interest.
*NB: compoundInterest = principal \* (Math.pow((1 + rate / 100), time)) - principal;*
*simpleInterest = (principal \* rate \* time) / 100;*

12. Write a Java program to calculate the power of a number by accepting the exponent and base from the user.

13. Write a Java program to count vowels and consonants in a string.

14. Write a Java program to reverse an array's elements (from the last element to the first).

15. Write a Java program to print the following patterns.

16. Write the output and explain the reasoning behind each result:

```java
public class PrintPattern {
public static void main(String[] args) {
int x = 14, y = 17;
System.out.println(x | y);
System.out.println(x & y);
System.out.println(x >> 2);
System.out.println(y >> 1);
System.out.println(x << 2);
}
}
```
*NB: Explain each output manually.*

17. Write a Java program to sum the values of an array and calculate the average value of the array. The array values are [tex]$1, 2, 3, 4, 5, 6, 78, 9, 10$[/tex].

18. Write a Java program to print odd and even numbers from an array element [tex]$\{1, 2, 3, 4, 5, 6, 7, 8, 9, 11\}$[/tex].

19. Write a Java program to find all roots of a quadratic equation.
*NB: [tex]$x = \left(-b \pm \sqrt{b^2 - 4ac}\right) / 2a$[/tex]*

20. Write a Java program to generate a multiplication table.

Answer :

Certainly! Let's tackle each Java programming task mentioned step by step:

1. Swap Two Variables in Java:
```java
public class SwapVariables {
public static void main(String[] args) {
int a = 5;
int b = 10;
System.out.println("Before swap: a = " + a + ", b = " + b);
// Swap logic
int temp = a;
a = b;
b = temp;
System.out.println("After swap: a = " + a + ", b = " + b);
}
}
```

2. Print a Face in Java:
```java
public class PrintFace {
public static void main(String[] args) {
System.out.println(" +\"\"\"\"\"+ ");
System.out.println("[| o o |]");
System.out.println(" | ^ | ");
System.out.println(" | '-' | ");
System.out.println(" +-----+ ");
}
}
```

3. Compare Three Numbers:
```java
import java.util.Scanner;

public class CompareNumbers {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.println("Enter three numbers: ");
int num1 = scanner.nextInt();
int num2 = scanner.nextInt();
int num3 = scanner.nextInt();

if (num1 >= num2 && num1 >= num3) {
System.out.println(num1 + " is the largest number.");
} else if (num2 >= num1 && num2 >= num3) {
System.out.println(num2 + " is the largest number.");
} else {
System.out.println(num3 + " is the largest number.");
}
}
}
```

4. Check Alphabet Using if-else:
```java
import java.util.Scanner;

public class CheckAlphabet {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.println("Enter a character: ");
char ch = scanner.next().charAt(0);

if ((ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z')) {
System.out.println(ch + " is an alphabet.");
} else {
System.out.println(ch + " is not an alphabet.");
}
}
}
```

5. Check Even or Odd Number:
```java
import java.util.Scanner;

public class EvenOrOdd {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.println("Enter a number: ");
int number = scanner.nextInt();

if (number % 2 == 0) {
System.out.println(number + " is even.");
} else {
System.out.println(number + " is odd.");
}
}
}
```

6. Find Factorial of a Number:
```java
import java.util.Scanner;

public class Factorial {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.println("Enter a number: ");
int number = scanner.nextInt();
long factorial = 1;

for (int i = 2; i <= number; i++) {
factorial = i;
}
System.out.println("Factorial of " + number + " is " + factorial);
}
}
```

7. Output for the PrintPattern Class:
Given a simple Java code snippet using loops to print a pattern of stars:
```

```

8. Check Vowel or Consonant Using if and switch:
```java
import java.util.Scanner;

public class VowelConsonant {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.println("Enter a character: ");
char ch = scanner.next().charAt(0);

if ((ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z')) {
switch (Character.toLowerCase(ch)) {
case 'a':
case 'e':
case 'i':
case 'o':
case 'u':
System.out.println(ch + " is a vowel.");
break;
default:
System.out.println(ch + " is a consonant.");
}
} else {
System.out.println(ch + " is not an alphabet.");
}
}
}
```

9. Explanation of Java Program ommissions:
a. Omitting 'main': Without the `main` method, the program won’t run as it's the entry point for any Java application.
b. Omitting 'String': The `main` method parameter, `String[] args`, is essential for command-line arguments; removing `String` will lead to a compilation error.
c. Omitting 'HelloWorld': Removing the original class name will cause a compilation error since the file name and the class name must match.
d. Omitting 'System.out': `System.out` is the standard output stream in Java; omitting it will result in errors when trying to print to the console.

These tasks cover a range of basic Java programming skills. Let me know if you need help with anything else!

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