给我100道JAVA编程练习题，从基础到高级，从简单到复杂，最好带有参考答案，有答案的最好带上答案

好的，以下是一些从基础到高级、从简单到复杂的Java编程练习题，包含参考答案：

1. 编写一个程序，计算并输出1到100之间所有整数的和。
答案：

public class SumOfNumbers {
    public static void main(String[] args) {
        int sum = 0;
        for (int i = 1; i <= 100; i++) {
            sum += i;
        }
        System.out.println("The sum of numbers from 1 to 100 is " + sum);
    }
}

2. 编写一个程序，输出100以内的所有偶数。
答案：

public class EvenNumbers {
    public static void main(String[] args) {
        for (int i = 2; i <= 100; i += 2) {
            System.out.println(i);
        }
    }
}

3. 编写一个程序，输出用户输入的整数是否为质数。
答案：

import java.util.Scanner;

public class PrimeNumber {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("Enter a number:");
        int num = scanner.nextInt();
        boolean isPrime = true;
        for (int i = 2; i < num; i++) {
            if (num % i == 0) {
                isPrime = false;
                break;
            }
        }
        if (isPrime) {
            System.out.println(num + " is a prime number.");
        } else {
            System.out.println(num + " is not a prime number.");
        }
    }
}

4. 编写一个程序，输出用户输入的字符串中的单词数。
答案：

import java.util.Scanner;

public class WordCount {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("Enter a string:");
        String str = scanner.nextLine();
        String[] words = str.split("\\s+");
        int count = words.length;
        System.out.println("The number of words in the string is " + count);
    }
}

5. 编写一个程序，实现一个简单的计算器，可以进行加、减、乘、除四种运算。
答案：

import java.util.Scanner;

public class Calculator {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("Enter the first number:");
        double num1 = scanner.nextDouble();
        System.out.println("Enter the second number:");
        double num2 = scanner.nextDouble();
        System.out.println("Enter the operator (+, -, *, /):");
        char operator = scanner.next().charAt(0);
        double result = 0;
        switch (operator) {
            case '+':
                result = num1 + num2;
                break;
            case '-':
                result = num1 - num2;
                break;
            case '*':
                result = num1 * num2;
                break;
            case '/':
                result = num1 / num2;
                break;
            default:
                System.out.println("Invalid operator.");
                return;
        }
        System.out.println(num1 + " " + operator + " " + num2 + " = " + result);
    }
}

6. 编写一个程序，实现一个简单的登录系统，要求用户输入用户名和密码，如果用户名和密码正确则