Java Basics Examples

public class Main {
    public static void main(String[] args) {
        int n = 7;
        int a = 0, b = 1;
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < n; i++) {
            sb.append(a);
            if (i < n-1) sb.append(" ");
            int next = a + b;
            a = b;
            b = next;
        }
        System.out.println(sb.toString());
    }
}

public class Main {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

public class Main {
    public static void main(String[] args) {
        int a = 12;
        int b = 30;
        int sum = a + b;
        System.out.println(sum);
    }
}

public class Main {
    public static void main(String[] args) {
        double n = 81.0;
        System.out.println(Math.sqrt(n));
    }
}

public class Main {
    public static void main(String[] args) {
        double base = 10, height = 5;
        double area = (base * height) / 2.0;
        System.out.println(area);
    }
}

public class Main {
    public static void main(String[] args) {
        int a = 3, b = 4;
        int temp = a;
        a = b;
        b = temp;
        System.out.println(a + " " + b);
    }
}

public class Main {
    public static void main(String[] args) {
        double a = 1, b = -3, c = 2;
        double d = b*b - 4*a*c;
        double r1 = (-b + Math.sqrt(d)) / (2*a);
        double r2 = (-b - Math.sqrt(d)) / (2*a);
        System.out.println(r1 + " " + r2);
    }
}

public class Main {
    public static void main(String[] args) {
        double km = 10.0;
        double miles = km * 0.621371;
        System.out.println(miles);
    }
}

public class Main {
    public static void main(String[] args) {
        double c = 25.0;
        double f = (c * 9/5) + 32;
        System.out.println(f);
    }
}

public class Main {
    public static void main(String[] args) {
        int n = 0;
        if (n > 0) System.out.println("positive");
        else if (n < 0) System.out.println("negative");
        else System.out.println("zero");
    }
}

public class Main {
    public static void main(String[] args) {
        int n = 7;
        System.out.println((n % 2 == 0) ? "even" : "odd");
    }
}

public class Main {
    public static void main(String[] args) {
        int n = 5;
        long fact = 1;
        for (int i = 2; i <= n; i++) fact *= i;
        System.out.println(fact);
    }
}

public class Main {
    static boolean isPrime(int n) {
        if (n < 2) return false;
        if (n % 2 == 0) return n == 2;
        for (int i = 3; i * i <= n; i += 2) {
            if (n % i == 0) return false;
        }
        return true;
    }

    public static void main(String[] args) {
        System.out.println(isPrime(29));
    }
}

import java.util.regex.*;
public class Main {
    public static void main(String[] args) {
        String s = "Hello World";
        Matcher m = Pattern.compile("[aeiouAEIOU]").matcher(s);
        int count = 0;
        while (m.find()) count++;
        System.out.println(count);
    }
}