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/**
* MIT License
*
* Copyright (c) 2017-2018 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.nio.file.Files;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.*;
import java.util.List;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;
/*
* Java Snippets code
*
*/
public class Library {
/**
* Generic 2 array concatenation
* Credits: Joachim Sauer https://stackoverflow.com/questions/80476/how-can-i-concatenate-two-arrays-in-java
* @param first is the first array (not null)
* @param second is the second array (not null)
* @param <T> the element type
* @return concatenated array
*/
public static <T> T[] arrayConcat(T[] first, T[] second) {
T[] result = Arrays.copyOf(first, first.length + second.length);
System.arraycopy(second, 0, result, first.length, second.length);
return result;
}
/**
* Generic N array concatenation
* Credits: Joachim Sauer https://stackoverflow.com/questions/80476/how-can-i-concatenate-two-arrays-in-java
* @param first is the first array (not null)
* @param rest the rest of the arrays (optional)
* @param <T> the element type
* @return concatenated array
*/
public static <T> T[] nArrayConcat(T[] first, T[]... rest) {
int totalLength = first.length;
for (T[] array : rest) {
totalLength += array.length;
}
T[] result = Arrays.copyOf(first, totalLength);
int offset = first.length;
for (T[] array : rest) {
System.arraycopy(array, 0, result, offset, array.length);
offset += array.length;
}
return result;
}
/**
* Recursive Fibonacci series
* Works only for small n and is spectacularly inefficient
* @param n
* @return fibonacci number for given n
*/
public static int fibonacci(int n) {
if (n <= 1) return n;
else return fibonacci(n-1) + fibonacci(n-2);
}
/**
* Factorial
* Works only for small numbers
* @param number for which factorial is to be calculated for
* @return factorial
*/
public static int factorial(int number) {
int result = 1;
for (int factor = 2; factor <= number; factor++) {
result *= factor;
}
return result;
}
/**
* Reverse string
* @param s the string to reverse
* @return reversed string
*/
public static String reverseString(String s) {
return new StringBuilder(s).reverse().toString();
}
/**
* Read file as list of strings
* @param filename the filename to read from
* @return list of strings
* @throws IOException
*/
public static List<String> readLines(String filename) throws IOException {
return Files.readAllLines(new File(filename).toPath());
}
/**
* Capture screenshot and save it to a file
* Credits: https://viralpatel.net/blogs/how-to-take-screen-shots-in-java-taking-screenshots-java/
* @param filename the name of the file
* @throws AWTException
* @throws IOException
*/
public static void captureScreen(String filename) throws AWTException, IOException {
Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
Rectangle screenRectangle = new Rectangle(screenSize);
Robot robot = new Robot();
BufferedImage image = robot.createScreenCapture(screenRectangle);
ImageIO.write(image, "png", new File(filename));
}
/**
* Convert string to date
* @param date the date string
* @param format expected date format
* @return Date
* @throws ParseException
*/
public static Date stringToDate(String date, String format) throws ParseException {
SimpleDateFormat simpleDateFormat = new SimpleDateFormat(format);
return simpleDateFormat.parse(date);
}
/**
* List directories
* @param path the path where to look
* @return array of File
*/
public static File[] listDirectories(String path) {
return new File(path).listFiles(File::isDirectory);
}
/**
* Checks if given string is palindrome (same forward and backward)
* Skips non-letter characters
* Credits: https://github.com/kousen/java_8_recipes
* @param s string to check
* @return true if palindrome
*/
public static boolean isPalindrome(String s) {
StringBuilder sb = new StringBuilder();
for (char c : s.toCharArray()) {
if (Character.isLetter(c)) {
sb.append(c);
}
}
String forward = sb.toString().toLowerCase();
String backward = sb.reverse().toString().toLowerCase();
return forward.equals(backward);
}
/**
* List files in directory
* @param folder the path where to look
* @return array of File
*/
public static File[] listFilesInDirectory(final File folder) {
return folder.listFiles(File::isFile);
}
/**
* Recursively list all the files in directory
* @param path the path to start the search from
* @return list of all files
*/
public static List<File> listAllFiles(String path) {
List<File> all = new ArrayList<>();
File[] list = new File(path).listFiles();
if (list != null) { // In case of access error, list is null
for (File f : list) {
if (f.isDirectory()) {
all.addAll(listAllFiles(f.getAbsolutePath()));
} else {
all.add(f.getAbsoluteFile());
}
}
}
return all;
}
/**
* Generate random lottery numbers
* @param numNumbers how many performLottery numbers are available (e.g. 49)
* @param numbersToPick how many numbers the player needs to pick (e.g. 6)
* @return array with the random numbers
*/
public static Integer[] performLottery(int numNumbers, int numbersToPick) {
List<Integer> numbers = new ArrayList<>();
for(int i = 0; i < numNumbers; i++) {
numbers.add(i+1);
}
Collections.shuffle(numbers);
return numbers.subList(0, numbersToPick).toArray(new Integer[numbersToPick]);
}
/**
* Zip single file
* @param srcFilename the filename of the source file
* @param zipFilename the filename of the destination zip file
* @throws IOException
*/
public static void zipFile(String srcFilename, String zipFilename) throws IOException {
File srcFile = new File(srcFilename);
try (
FileOutputStream fileOut = new FileOutputStream(zipFilename);
ZipOutputStream zipOut = new ZipOutputStream(fileOut);
FileInputStream fileIn = new FileInputStream(srcFile);
) {
ZipEntry zipEntry = new ZipEntry(srcFile.getName());
zipOut.putNextEntry(zipEntry);
final byte[] bytes = new byte[1024];
int length;
while ((length = fileIn.read(bytes)) >= 0) {
zipOut.write(bytes, 0, length);
}
}
}
/**
* Zip multiples files
* @param srcFilenames array of source file names
* @param zipFilename the filename of the destination zip file
* @throws IOException
*/
public static void zipFiles(String[] srcFilenames, String zipFilename) throws IOException {
try (
FileOutputStream fileOut = new FileOutputStream(zipFilename);
ZipOutputStream zipOut = new ZipOutputStream(fileOut);
) {
for (int i=0; i<srcFilenames.length; i++) {
File srcFile = new File(srcFilenames[i]);
try (FileInputStream fileIn = new FileInputStream(srcFile)) {
ZipEntry zipEntry = new ZipEntry(srcFile.getName());
zipOut.putNextEntry(zipEntry);
final byte[] bytes = new byte[1024];
int length;
while ((length = fileIn.read(bytes)) >= 0) {
zipOut.write(bytes, 0, length);
}
}
}
}
}
/**
* Sort an array with quicksort algorithm
* @param arr array to sort
* @param left left index where to begin sort (e.g. 0)
* @param right right index where to end sort (e.g. array length - 1)
*/
public static void quickSort(int[] arr, int left, int right) {
int pivotIndex = left + (right - left) / 2;
int pivotValue = arr[pivotIndex];
int i = left, j = right;
while (i <= j) {
while (arr[i] < pivotValue) {
i++;
}
while (arr[j] > pivotValue) {
j--;
}
if (i <= j) {
int tmp = arr[i];
arr[i] = arr[j];
arr[j] = tmp;
i++;
j--;
}
if (left < i) {
quickSort(arr, left, j);
}
if (right > i) {
quickSort(arr, i, right);
}
}
}
/**
* Performs HTTP GET request
* @param address the URL of the connection
* @return HTTP status code
* @throws IOException
*/
public static int httpGet(URL address) throws IOException {
HttpURLConnection con = (HttpURLConnection) address.openConnection();
return con.getResponseCode();
}
/**
* Checks if given number is a prime number
* Prime number is a number that is greater than 1 and divided by 1 or itself only
* Credits: https://en.wikipedia.org/wiki/Prime_number
* @param number number to check prime
* @return true if prime
*/
public static boolean isPrime(int number) {
if (number < 3) {
return true;
}
// check if n is a multiple of 2
if (number % 2 == 0) {
return false;
}
// if not, then just check the odds
for (int i = 3; i * i <= number; i += 2) {
if (number % i == 0) {
return false;
}
}
return true;
}
}