Lesson 3 Homework 1-5

Homework1.java

package lesson3;

public class Homework1 {

	public static void main(String[] args) {
		
		double[] num = {1.0, 4.0, 9.0, 1.0};
		System.out.println(findElement(num, 1.0));
		System.out.println(findElement(num, 4.0));
		System.out.println(findElement(num, 22.0));
	}

	static int findElement(double[] numbers, double el) {
		
		for (int i = 0; i < numbers.length; i ++) {
			if (numbers[i] == el) {
				return i;
			}
		}
		return -1;
	}
}

Homework2.java

package lesson3;

import java.util.Arrays;

public class Homework2 {

	public static void main(String[] args) {
		
		int[] arr = {0, 1, 2};
		int[] arr2 = new int[2];
		
		System.out.println("arr " + Arrays.toString(arr) + " arr2 " + Arrays.toString(arr2));
		copyArray(arr, 0, arr2, 0, 2);
		System.out.println("arr " + Arrays.toString(arr) + " arr2 " + Arrays.toString(arr2));
	}
	
	static void copyArray(int[] src, int srcPos, int[] dest, int destPos, int length) {
		
		for (int i = srcPos, j = destPos; i < length; i++, j++) {
			dest[j] = src[i];
		}
	}
}

Homework3.java

package lesson3;

public class Homework3 {

	public static void main(String[] args) {
		
		System.out.println(inverse("Happy Birthday!"));
		System.out.println(inverse("Happy Birthday"));
	}
	
	static String inverse(String str) {
		
		char[] charStr = str.toCharArray();
		char[] charStr2 = new char[charStr.length];
		
		for (int i = 0, j = charStr.length - 1; i < charStr.length; i++, j--) {
			charStr2[j] = charStr[i];
		}
		return new String(charStr2);
	}

Homework4.java

package lesson3;

public class Homework4 {

	public static void main(String[] args) {
		
		System.out.println(factorial(3));
		System.out.println(factorial(5));
		System.out.println(factorial(1));
	}
	
	static long factorial(int i) {
		
		if (i <= 0) {
			return 1;
		}
		
		long res = 1;
		for (int j = 1; j <= i; j++) {
			res = res * j;
		}
		return res;
	}
}

Homework5.java

package lesson3;

public class Homework5 {

	public static void main(String[] args) {
		
		String[][] arr1 = {{"oleg"},  {"Inna", "Smith", "25"}, {"Irina", "Koval"}};
		String[][] arr2 = {{},  {}};
		String[][] arr3 = {{},  {"Boris", "Govor", "66"}, {}};
		String[][] arr4 = {{"oleg"}, {"anton"}, null, {"Anna", "25"}};
		
		printArray(arr1);
		printArray(arr2);
		printArray(arr3);
		printArray(arr4);
	}
	
	static void printArray(String[][] data) {
		
		String result = "";
		
		if (data != null) {
			for (int i = 0; i < data.length; i++) {
				System.out.print("{");
				
				if (data[i] != null) {
					for (int j = 0; j < data[i].length; j++) {
						
						if (data[i][j] != null) {
						result = data[i][j] ;
						System.out.print(" " + result + " ");
						}
						else System.out.print("");
					}
				}
				System.out.print("}");
			}
			System.out.println();
		}
	}
}