Converting an uppercase letter to lowercase

import java.util.Scanner;

public class ConvertUperToLower

{

public static void main(String[] args)

{

Scanner scanner = new Scanner(System.in);

String string;

int i = 0;

int offset = 'a' - 'A';

System.out.print("Enter a string: ");

string = scanner.next();

System.out.println("The input string is: " + string);

char[] ch = new char[string.length()];

ch = string.toCharArray();

i = 0;

System.out.print("The convert result is: ");

while(i < string.length())

{

if (ch[i] >= 'A' && ch[i] <= 'Z')

{

ch[i] += offset;

}

System.out.printf("%c", ch[i]);

i++;

}

}

}

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import javax.swing.*;

public class AdditionTutor

{

public static void main(String[] args)

{

while(true)

{

int number1 = (int)(System.currentTimeMillis() % 10);

int number2 = (int)(System.currentTimeMillis() * 7 % 10);

String answerString = JOptionPane.showInputDialog("What is " + number1

+ " + " + number2 + "?");

int answer = Integer.parseInt(answerString);

JOptionPane.showMessageDialog(null, number1 + " + "

+ number2 + " = " + answer + " is " + (number1 + number2 == answer));

}

}

}

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import javax.swing.JOptionPane;

public class SubtractionTutor

{

public static void main(String[] args)

{

while(true)

{

int number1 = (int)(Math.random() * 10);

int number2 = (int)(Math.random() * 10);

if (number1 < number2)

{

int temp = number1;

number1 = number2;

number2 = temp;

}

String answerString = JOptionPane.showInputDialog("What is " + number1

+ " - " + number2 + "?");

int answer = Integer.parseInt(answerString);

String replyString;

if (number1 - number2 == answer)

{

replyString = "You are correct!";

}

else

{

replyString = "Your answer is wrong.\n" + number1 + " - "

+ number2 + " should be " + (number1 = number2);

}

JOptionPane.showMessageDialog(null, replyString);

}

}

}