Lessons6Example1

package com.gmail.kudr641;

import java.util.Calendar;
import java.util.Date;

public class Lessons6Example1 {

	public static void main(String[] args) {
		Date nowDate = new Date();

		Calendar calendar = Calendar.getInstance();

		calendar.setTime(nowDate);

		int nowYear = calendar.get(Calendar.YEAR);
		int nowMonth = calendar.get(Calendar.MONTH);
		int nowDay = calendar.get(Calendar.DAY_OF_MONTH);

		Calendar lastCalendar = Calendar.getInstance();

		lastCalendar.set(nowYear, nowMonth - 1, nowDay);

		long nowTime = calendar.getTimeInMillis();
		long lastTime = lastCalendar.getTimeInMillis();

		System.out.println(nowTime - lastTime);

	}

}

Lessons6Example2

package com.gmail.kudr641;

import java.util.Random;
import java.util.Scanner;

public class Lessons6Example2 {

	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		Random random = new Random();
		
		System.out.println("Input size array:");
		int size = scanner.nextInt();
		
		scanner.close();
		
		int[] array = new int[size];
		for(int i = 0;i < array.length; i += 1){
			array[i] = random.nextInt(10);
		}
		String str = arrayToString(array);
		
		System.out.println(str);
	}

	static String arrayToString(int[] array){
		StringBuilder sb = new StringBuilder("");		
		sb.append('[');		
		for(int i = 0; i < array.length; i += 1){		
			if(i < array.length - 1){				
				sb.append(array[i] + ", ");				
			}else{				
				sb.append(array[i]);				
			}					
		}		
		sb.append(']');
		return sb.toString();
	}
}

Lessons6Example3

package com.gmail.kudr641;

import java.util.Scanner;

public class Lessons6Example3 {

	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);

		System.out.println("Type a number in binary form:");
		String number = scanner.nextLine();
		scanner.close();

		printResult(number);
	}

	static boolean ifBinary(String number) {
		boolean binary = true;
		for (int i = 0; i < number.length(); i += 1) {
			if (number.charAt(i) != '0' && number.charAt(i) != '1') {
				binary = false;
				break;
			}
		}
		return binary;
	}

	static void printResult(String number) {
		if (ifBinary(number)) {
			int sum = 0;
			for (int i = number.length() - 1, j = 0; i >= 0; i -= 1, j += 1) {
				int x = Character.getNumericValue(number.charAt(j));
				int multiplication = x * (1 << i);
				sum += multiplication;
			}
			System.out.println("The number in decimal format: " + sum);
		} else {
			System.out.println("This number is in binary format!");
		}
	}
}

Lessons6Example4

package com.gmail.kudr641;

import java.util.Formatter;

public class Lessons6Example4 {

	public static void main(String[] args) {		

		Formatter formatter = new Formatter();
		for (int i = 2; i <= 12; i += 1) {			
						
			formatter.format("%."+ i +"f", Math.PI);

			String pi = formatter.toString();

			System.out.println(pi);
		}
		formatter.close();

	}

}