Laboratory Activity: Loop Structure

EvenNum.java

import java.util.Scanner;

public class EvenNum {

	public static void main(String[] args) {
		Scanner sc = new Scanner (System.in);
		System.out.println("Program: EVEN NUMBERS FROM 1-50\n");
		System.out.println("Even Number from 1 to 50...");
		System.out.println("----------using for loop----------");
		for(int i = 1; i<=50; i++) {
			if(i%2 == 0) System.out.print(i + " ");
		}
		System.out.println("\n----------using while loop----------");
		int i = 1;
		while (i <= 50) {
			if (i%2 == 0) System.out.print(i + " ");
		i++;
		}
		System.out.println("\n----------using do...while loop----------");
		i = 1;
		do {
			if (i%2 == 0) System.out.print(i + " ");
			i++;
		}
		while(i <= 50);
	}

}

InterestRate.java

import java.util.*;
public class InterestRate
{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		double balance = 0, rate = 0.025;
		boolean loop = true;
		char option;
		System.out.println("Program: Bank Interest Rate\n");
		while (loop){
			System.out.print("Enter d for deposit, w for withdrawal or x to exit: ");
			option = sc.nextLine().charAt(0);
			balance+=balance*(0.025/12);
			switch(option){
				case 'e':
					loop = false;
					System.out.println("Balance after transaction: "+balance+"\n");
					break;
				case 'd':
					System.out.println("Beginning of Month Balance: "+balance);
					System.out.print("Enter deposit amount: ");
					double deposit = sc.nextDouble();
					balance+=deposit;
					System.out.println("Balance after transaction: "+balance+"\n");
					break;
				case 'w':
					System.out.println("Beginning of Month Balance: "+balance);
					System.out.print("Enter withdrawal amount: ");
					double withdraw = sc.nextDouble();
					balance-=withdraw;
					System.out.println("Balance after transaction: "+balance+"\n");
					break;
				default:
					System.err.println("Error: Invalid choice.");
			}
			sc.nextLine();
		}
	}
}

NameValidation.java

import java.util.Scanner;

public class NameValidation {

	public static void main(String[] args) {
		Scanner sc = new Scanner (System.in);
		System.out.println("Program: NAME VALIDATION\n");
		System.out.println("Using the while loop...");
		boolean loop = true;
		while(loop) { // flag-controlled
			System.out.print("Enter a word: ");
			String str = sc.next();
			if (str.equalsIgnoreCase("exit")) {
				System.out.println("Program is now terminating…");
				loop = false; // or just break; will do
			}
			else if (str.charAt(0) == str.charAt(str.length()-1))
				System.out.println("The first character is equal to its last character: "+str+"\n");
			else System.out.println("The first character is not equal to its last character: "+str+"\n");
		}
		System.out.println("\nUsing the do-while loop...");
		loop = true;
		do{
			System.out.print("Enter a word: ");
			String str = sc.next();
			if (str.equalsIgnoreCase("exit")) {
				System.out.println("Program is now terminating…");
				loop = false; // or just break; will do
			}
			else if (str.charAt(0) == str.charAt(str.length()-1))
				System.out.println("The first character is equal to its last character: "+str+"\n");
			else System.out.println("The first character is not equal to its last character: "+str+"\n");
		} while (loop); // flag-controlled
	}
}

Prime.java

import java.util.Scanner;

public class Prime {

	public static void main(String[] args) {
		Scanner sc = new Scanner (System.in);
		System.out.println("Program: PRIME NUMBERS\n");
		System.out.print("Enter number: ");
		int n = sc.nextInt();
		int i = 2;
		boolean loop = true;
		while (loop) {
			if (i < n)
				if (n%i == 0) {
					System.out.println("Not Prime");
					loop = false;
				}
				else i++;
			else {
				System.out.println("Prime");
				loop = false;
			}
		}
	}
}

StringManipulation.java

import javax.swing.JOptionPane;

public class StringManipulation {

	public static void main(String[] args) {
		boolean loop = true;
		while(loop) {
			String str = JOptionPane.showInputDialog("Enter string:");
			if (str == null || str.equals("DONE")) {
				int response = JOptionPane.showConfirmDialog(null, "Are you sure you want to exit?", "Exit", JOptionPane.YES_NO_OPTION);
				if (response == 0) loop = false;
			}
			else if (str.equals(""))
				JOptionPane.showMessageDialog(null, "You typed a blank input. Please try again.", "Error", JOptionPane.ERROR_MESSAGE);
			else {
				str.toLowerCase();
				int special = 0, consonants = 0, vowels = 0, odds = 0, evens = 0;
				for (int i = 0, len = str.length()-1; i <= len;i++) {
					char x = str.charAt(i);
					if(Character.isLetter(x)) {
						if (x == 'a' || x == 'e' || x == 'i' || x == 'o' || x == 'u')
							vowels++;
						else consonants++;
					}
					else if (Character.isDigit(x)) {
						if (x%2 == 0) evens++;
						else odds++;
					}
					else special++;
					if(i == len)
						JOptionPane.showMessageDialog(null, String.format("String: %s\n\n"
								+ "Special Characters: %d\nConsonants: %d"
								+ "\nVowels: %d\nOdd Numbers: %d\nEven Numbers: %d", str, special, consonants, vowels, odds, evens), "Result", JOptionPane.INFORMATION_MESSAGE);
					}
				}
			}
		}
	}

Sum50.java

import java.util.Scanner;

public class Sum50 {

	public static void main(String[] args) {
		Scanner sc = new Scanner (System.in);
		System.out.println("Program: SUM OF NUMBERS FROM 1-50\n");
		int sum = 0;
		for(int i = 50; i > 0; i--) //decrement
			sum+=i;
		System.out.println("Sum of numbers from 1 to 50: "+sum);
	}

}

SumofNPositiveOdds.java

import java.util.Scanner;

public class SumofNPositiveOdds {

	public static void main(String[] args) {
		Scanner sc = new Scanner (System.in);
		System.out.println("Program: SUM OF POSITIVE ODD INTEGERS FROM 1 TO N\n");
		System.out.print("Enter n: ");
		int n = sc.nextInt();
		int sum = 0;
		for (int i = 1, j = 1; i <= n; i++) {
			sum+=j;
			j+=2;
		}
		System.out.println("Result: "+sum);
	}

}

SumOfNSquares.java

import java.util.Scanner;

public class SumOfNSquares {

	public static void main(String[] args) {
		Scanner sc = new Scanner (System.in);
		System.out.println("Program: SUM OF SQUARES FROM 1 TO N\n");
		System.out.print("Enter n: ");
		int n = sc.nextInt();
		int sum = 0;
		for (int i = 1; i <= n; i++) {
			sum+=(i*i);
		}
		System.out.println("Result: "+sum);
	}

}

TableOfSquares.java

import java.util.Scanner;

public class TableOfSquares {

	public static void main(String[] args) {
		Scanner sc = new Scanner (System.in);
		System.out.println("Program: TABLE OF SQUARES\n");
		System.out.println("-------Using for loop----------");
		for (int i = 0; i <= 20; i++)
			System.out.printf("Number : %d\tSquare : %d\n", i, i*i); // Using String Formatter
		System.out.println("\n-------Using while loop--------");
		int i = 1;
		while(i <= 20) {
			System.out.printf("Number : %d\tSquare : %d\n", i, i*i); // Using String Formatter
			i++;
		}
		System.out.println("\n-------Using do...while loop------");
		i = 1;
		do {
			System.out.printf("Number : %d\tSquare : %d\n", i, i*i); // Using String Formatter
			i++;
		}while(i <= 20);
	}

}

WhiteSpaceCounter.java

import java.util.Scanner;

public class WhiteSpaceCounter {

	public static void main(String[] args) {
		Scanner sc = new Scanner (System.in);
		System.out.println("Program: WHITESPACES COUNTER\n");
		System.out.print("Enter string: ");
		String str = sc.nextLine();
		int whitespaces = 0;
		for (int i = 0, len = str.length()-1; i <= len;i++) {
			char x = str.charAt(i);
			if (Character.isWhitespace(x)) {
				whitespaces++;
			}
			}
		System.out.println("Result: "+whitespaces);
	}
}